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  • 251.
    Sandborg, Michael
    et al.
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics UHL.
    Rossitti, Sandro
    Linköping University, Department of Clinical and Experimental Medicine. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Sinnescentrum, Department of Neurosurgery UHL.
    Pettersson, Håkan
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics UHL.
    Nilsson Althen, Jonas
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics UHL.
    Patient organ radiation doses during treatment for aneurismal subarachnoid haemorrhage2011Conference paper (Other academic)
  • 252.
    Sandborg, Michael
    et al.
    Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Linköping University, Faculty of Health Sciences.
    Tingberg, Anders
    Department of Radiation Physics, Malmö University Hospital, Malmö, Sweden.
    Ullman, Gustaf
    Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Linköping University, Faculty of Health Sciences.
    Dance, David R.
    Joint Department of Physics, The Royal Marsden NHS Trust and Institute of Cancer Research, London.
    Alm Carlsson, Gudrun
    Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Linköping University, Faculty of Health Sciences.
    Comparison of clinical and physical measures of image quality in chest and pelvis computed radiography at different tube voltages2006In: Medical physics (Lancaster), ISSN 0094-2405, Vol. 33, no 11, p. 4169-4175Article in journal (Refereed)
    Abstract [en]

    The aim of this work was to study the dependence of image quality in digital chest and pelvis radiography on tube voltage, and to explore correlations between clinical and physical measures of image quality. The effect on image quality of tube voltage in these two examinations was assessed using two methods. The first method relies on radiologists' observations of images of an anthropomorphic phantom, and the second method was based on computer modeling of the imaging system using an anthropomorphic voxel phantom. The tube voltage was varied within a broad range (50–150  kV), including those values typically used with screen-film radiography. The tube charge was altered so that the same effective dose was achieved for each projection. Two x-ray units were employed using a computed radiography (CR) image detector with standard tube filtration and antiscatter device. Clinical image quality was assessed by a group of radiologists using a visual grading analysis (VGA) technique based on the revised CEC image criteria. Physical image quality was derived from a Monte Carlo computer model in terms of the signal-to-noise ratio, SNR, of anatomical structures corresponding to the image criteria. Both the VGAS (visual grading analysis score) and SNR decrease with increasing tube voltage in both chest PA and pelvis AP examinations, indicating superior performance if lower tube voltages are employed. Hence, a positive correlation between clinical and physical measures of image quality was found. The pros and cons of using lower tube voltages with CR digital radiography than typically used in analog screen-film radiography are discussed, as well as the relevance of using VGAS and quantum-noise SNR as measures of image quality in pelvis and chest radiography.

  • 253.
    Sandström, Per
    et al.
    Linköping University, Department of Clinical and Experimental Medicine, Surgery. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Surgery in Östergötland.
    Dahlqvist Leinhard, Olof
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Dahlström, Nils
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences.
    Freij, Anna
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Kihlberg, Johan
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences.
    Brismar, Torkel
    Karolinska University Hospital, Stockholm, Sweden .
    Smedby, Örjan
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Lundberg, Peter
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics.
    Upptag i levern av kontrastmedlet Gd-EOB-DTPA påverkas kraftigt av leverfunktionen2009Conference paper (Other academic)
  • 254. Sastry, M.D.
    et al.
    Gustafsson, Håkan
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Health Sciences, Radiation Physics .
    Danilczuk, M.
    Lund, Anders
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Chemical Physics .
    Dynamical effects and ergodicity in the dipolar glass phase: Evidence from time-domain EPR and phase memory time studies of AsO44- in Rb1-x(NH4)xH2PO4 (x = 0,0.5,1)2006In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 18, no 17, p. 4265-4284Article in journal (Refereed)
    Abstract [en]

    Three-pulse electron spin echo envelope modulation (ESEEM), hyperfine sublevel correlation spectroscopy (HYSCORE) investigations and two-pulse electron spin echo (ESE) measurements of phase memory time TM, were carried out, in the 20-200 K temperature range, on an AsO44- paramagnetic probe stabilized in RbH2PO4 (RDP), NH4H2PO4 (ADP), and dipolar glass Rb0.5(NH4)0.5H2PO4 (RADP). The results obtained on ADP revealed hyperfine interaction of the probe ion with the 14N of the ammonium ion, the coupling constant satisfying the condition of 'cancellation' at a field of 480 mT. The ammonium ion was found to be in two different sites in ADP, which became indistinguishable on the formation of dipolar glass RADP. These results were confirmed by HYSCORE spectral measurements. The fast Fourier transform (FFT) spectra of three-pulse ESEEM decays have clearly revealed the interaction with protons in the bond both in ADP and RDP, and in RADP with an averaged coupling constant. The phase memory times in RADP exhibited strong temperature dependence and were found to be dependent on the nuclear spin quantum number mI of 75As. The temperature dependence of TM exhibited a well-defined maximum around 90 K, coinciding with the temperature of onset of 'freezing' in Rb0.5(NH4)0.5H2PO 4. This is symptomatic of dynamic fluctuations in the dipolar glass phase, with onset around 150 K, going through a maximum around 90 K and slowing down on further cooling. These results suggest that in RADP, a dynamical mechanism with progressive slowing down below 90 K is operative in the glass formation. This implies that the RADP system, with x = 0.5, exists in an ergodic relaxor (R)-state in the 20-200 K temperature range wherein every fluctuating monodomain can be viewed as statistically representative of the whole sample. © IOP Publishing Ltd.

  • 255. Sjoholm, B
    et al.
    Geijer, H
    Persliden, Jan
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics.
    Impact of digital imaging on radiation doses to the patient during X-ray examination of the urinary tract2005In: Acta Radiologica, ISSN 0284-1851, E-ISSN 1600-0455, Vol. 46, no 6, p. 657-661Article in journal (Refereed)
    Abstract [en]

    Purpose: To compare radiation doses given to patients undergoing IVU (intravenous urography) before and after digitalization of our X-ray department. Material and Methods: IVU examinations were monitored with dose area product meters before and after the X-ray department changed to digital techniques. The first step was a change from film-screen to storage phosphor plates, while the second step involved changing to a flat panel detector. Forty-two patients were included for the film-screen situation, 69 when using the storage phosphor plates, and 70 using the flat panel detector. Results: A dose reduction from 41.8 Gycm(2) to 31.5 Gycm(2) was achieved with the first step when the film-screen system was replaced with storage phosphor plates. A further reduction to 12.1 Gycm(2) was achieved using the flat panel detector. Conclusion: The introduction of the flat panel detectors made a considerable dose reduction possible.

  • 256.
    Slatkin, Daniel
    et al.
    Brookhaven National Laboratory.
    Spanne, Per
    Brookhaven National Laboratory.
    Dilmanian, Avraham
    Brookhaven National Laboratory.
    Sandborg, Michael
    Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Linköping University, Center for Medical Image Science and Visualization, CMIV. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics.
    Microbeam Radiation Therapy1992In: Medical physics (Lancaster), ISSN 0094-2405, Vol. 19, p. 1395-1400Article in journal (Refereed)
    Abstract [en]

    It is proposed to carry out radiotherapy and radiosurgery for brain lesions by crossfiring an array of parallel, closely spaced microbeams of synchrotron-generated x rays several times through an isocentric target, each microbeam in the array having an 25-µm-wide adjustable-height rectangular cross section. The following inferences from the known tissue sparing of 22-MeV deuteron microbeams in the mouse brain and the following exemplary Monte Carlo computations indicate that endothelial cells in the brain that are lethally irradiated by any microbeam in an array of adequately spaced microbeams outside an isocentric target will be replaced by endothelial cells regenerated from microscopically contiguous, minimally irradiated endothelium in intermicrobeam segments of brain vasculature. Endothelial regeneration will prevent necrosis of the nontargeted parenchymal tissue. However, neoplastic and/or nonneoplastic targeted tissues at the isocenter will be so severely depleted of potentially mitotic endothelial and parenchymal cells by multiple overlapping microbeams that necrosis will ensue. The Monte Carlo computations simulate microbeam irradiations of a 16-cm diameter, 16-cm-long cylindrical human head phantom using 50-, 100-, and 150-keV monochromatic x rays.

  • 257.
    Smedby, Örjan
    et al.
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Fredrikson, Mats
    Linköping University, Department of Clinical and Experimental Medicine, Occupational and Environmental Medicine. Linköping University, Faculty of Health Sciences.
    de Geer, Jakob
    Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences.
    Borgen, L
    Drammen Hospital, Norway .
    Sandborg, Michael
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics.
    Quantifying the potential for dose reduction with visual grading regression2013In: British Journal of Radiology, ISSN 0007-1285, E-ISSN 1748-880X, Vol. 86, no 1021Article in journal (Refereed)
    Abstract [en]

    Objectives To propose a method to study the effect of exposure settings on image quality and to estimate the potential for dose reduction when introducing dose-reducing measures.

    Methods Using the framework of visual grading regression (VGR), a log(mAs) term is included in the ordinal logistic regression equation, so that the effect of reducing the dose can be quantitatively related to the effect of adding post-processing. In the ordinal logistic regression, patient and observer identity are treated as random effects using generalised linear latent and mixed models. The potential dose reduction is then estimated from the regression coefficients. The method was applied in a single-image study of coronary CT angiography (CTA) to evaluate two-dimensional (2D) adaptive filters, and in an image-pair study of abdominal CT to evaluate 2D and three-dimensional (3D) adaptive filters.

    Results For five image quality criteria in coronary CTA, dose reductions of 16–26% were predicted when adding 2D filtering. Using five image quality criteria for abdominal CT, it was estimated that 2D filtering permits doses were reduced by 32–41%, and 3D filtering by 42–51%.

    Conclusions VGR including a log(mAs) term can be used for predictions of potential dose reduction that may be useful for guiding researchers in designing subsequent studies evaluating diagnostic value. With appropriate statistical analysis, it is possible to obtain direct numerical estimates of the dose-reducing potential of novel acquisition, reconstruction or post-processing techniques.

  • 258.
    Smedby, Örjan
    et al.
    Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Fredrikson, Mats
    Linköping University, Department of Clinical and Experimental Medicine, Occupational and Environmental Medicine. Linköping University, Faculty of Health Sciences.
    de Geer, Jakob
    Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences.
    Sandborg, Michael
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Quantifying effects of post-processing with visual grading regression2012In: Medical Imaging 2012: Image Perception, Observer Performance, and Technology Assessment / [ed] Craig K. Abbey; Claudia R. Mello-Thoms, SPIE - International Society for Optical Engineering, 2012, Vol. 8318, p. Art. no. 83181N-Conference paper (Refereed)
    Abstract [en]

    For optimization and evaluation of image quality, one can use visual grading experiments, where observers rate some aspect of image quality on an ordinal scale. To take into account the ordinal character of the data, ordinal logistic regression is used in the statistical analysis, an approach known as visual grading regression (VGR). In the VGR model one may include factors such as imaging parameters and post-processing procedures, in addition to patient and observer identity. In a single-image study, 9 radiologists graded 24 cardiac CTA images acquired with ECG-modulated tube current using standard settings (310 mAs), reduced dose (62 mAs) and reduced dose after post-processing. Image quality was assessed using visual grading with five criteria, each with a five-level ordinal scale from 1 (best) to 5 (worst). The VGR model included one term estimating the dose effect (log of mAs setting) and one term estimating the effect of postprocessing. The model predicted that 115 mAs would be required to reach an 80% probability of a score of 1 or 2 for visually sharp reproduction of the heart without the post-processing filter. With the post-processing filter, the corresponding figure would be 86 mAs. Thus, applying the post-processing corresponded to a dose reduction of 25%. For other criteria, the dose-reduction was estimated to 16-26%. Using VGR, it is thus possible to quantify the potential for dose-reduction of post-processing filters.

  • 259.
    Smedby, Örjan
    et al.
    Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Fredrikson, Mats
    Linköping University, Department of Clinical and Experimental Medicine, Occupational and Environmental Medicine. Linköping University, Faculty of Health Sciences.
    de Geer, Jakob
    Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences.
    Sandborg, Michael
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Visual grading regression with random effects2012In: MEDICAL IMAGING 2012: IMAGE PERCEPTION, OBSERVER PERFORMANCE, AND TECHNOLOGY ASSESSMENT, SPIE - International Society for Optical Engineering, 2012, Vol. 8318, p. Art. no. 831805-Conference paper (Refereed)
    Abstract [en]

    To analyze visual grading experiments, ordinal logistic regression (here called visual grading regression, VGR) may be used in the statistical analysis. In addition to types of imaging or post-processing, the VGR model may include factors such as patient and observer identity, which should be treated as random effects. Standard software does not allow random factors in ordinal logistic regression, but using Generalized Linear Latent And Mixed Models (GLLAMM) this is possible. In a single-image study, 9 radiologists graded 24 cardiac Computed Tomography Angiography (CTA) images with reduced dose without and after post-processing with a 2D adaptive filter, using five image quality criteria. First, standard ordinal logistic regression was carried out, treating filtering, patient and observer identity as fixed effects. The same analysis was then repeated with GLLAMM, treating filtering as a fixed effect and patient and observer identity as random effects. With both approaches, a significant effect (pless than0.01) of the filtering was found for all five criteria. No dramatic differences in parameter estimates or significance levels were found between the two approaches. It is concluded that random effects can be appropriately handled in VGR using GLLAMM, but no major differences in the results were found in a preliminary evaluation.

  • 260.
    Stark, K.
    et al.
    Department of Systems Ecology, Stockholm University, Stockholm 106 91, Sweden.
    Pettersson, Håkan
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics.
    External radiation doses from 137Cs to frog phantoms in a wetland area: In situ measurements and dose model calculations2008In: Radiation and Environmental Biophysics, ISSN 0301-634X, E-ISSN 1432-2099, Vol. 47, no 4, p. 481-489Article in journal (Refereed)
    Abstract [en]

    For assessment of external radiation doses to frogs in a wetland area contaminated with 137Cs, frog phantoms were constructed from polymethyl methacrylate (PMMA). The frog phantoms contained thermoluminescence (TL) chips and were used in situ at two study sites to measure doses. To test if higher doses are received by the sensitive skin of frogs, extra-thin TL chips were applied close to the surface of the frog phantoms. In addition, the measured doses were compared with those calculated on the basis of soil sample data from the wetland multiplied with dose-conversion coefficients from the US Department of Energy's RESRAD-BIOTA code and from the ERICA assessment tool. Measured doses were generally lower than those calculated to ellipsoids used to model frogs. Higher doses were measured at the frog phantoms' surfaces in comparison to inner parts at one of the two sites indicating that the frogs' thin skin could receive a higher radiation dose than expected. In the efforts to assure protection of non-human biota, in situ measurements with phantoms provide valuable dose information and input to dose models in site-specific risk assessments of areas contaminated with radionuclides. © 2008 Springer-Verlag.

  • 261.
    Stark, Karolina
    et al.
    Stockholm University .
    Pettersson, Håkan B L
    Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics.
    Response to "On the calculation of external radiation doses from Cs-137 to frog phantoms in a wetland area" by G. Prohl and A. Ulanovsky2009In: RADIATION AND ENVIRONMENTAL BIOPHYSICS, ISSN 0301-634X, Vol. 48, no 2, p. 245-246Article in journal (Other academic)
  • 262.
    Stenström, Mats
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Computerised Microtomography: Non-invasive imaging and analysis of biological samples, with special reference to monitoring development of osteoporosis in small animals2001Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The use of Computerised microtomography (CμT) in biomedical research is well established, with most applications developed at synchrotron facilities. The possibility to non-invasively monitor morphological changes in biological samples, makes it an attractive technique in biomedicine. However, high absorbed doses and long examination times are a disadvantage that limits the possibilities of performing longitudinal examinations.

    The aim of this work was to optimise CmT using conventional X-ray tubes for applications in non-destructive material testing and for skeleton research in small animals (rat). A calculational model of the imaging system was developed and used to optimise the relation between image quality, expressed as the signal-to-noise ratio (SNR) in detecting a contrasting detail, and imaging time in material testing. The model was modified to optimise the relation between the SNR in detecting a trabecular detail in cancelleous bone and the mean absorbed dose in spongiosa and skin for (rat) tibia and femur.

    Gastrectomized Sprague-Dawley rats were used to initiate osteoporotic changes. In order to detect differences in between gastrectomized rats and controls, spatial resolutions of 150 mm or better were needed. The minimum absorbed doses in femur spongiosa at SNR = 5 were 1mGy - 700 mGy at spatial resolutions from 100 mm to10 mm. In femur skin, the corresponding minimum absorbed doses were 2 mGy - 2000 mGy. Corresponding values for tibia were 0.3 mGy - 300 mGy for both spongiosa and skin (spatial resolution of 100 mm to10 mm). Taking 0.5 Gy as the tolerance limit for the spongiosa dose, longitudinal studies with six repeated examinations will be possible at a spatial resolution of 25 mm in femur and 17 examinations in tibia.

    List of papers
    1. Methodologic aspects of computed microtomography to monitor the development of osteoporosis in gastrectomized rats
    Open this publication in new window or tab >>Methodologic aspects of computed microtomography to monitor the development of osteoporosis in gastrectomized rats
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    1995 (English)In: Academic Radiology, ISSN 1076-6332, Vol. 2, no 9, p. 785-791Article in journal (Refereed) Published
    Abstract [en]

    Rationale and Objectives

    We investigated the methodologic development of computed microtomography (CMT) for monitoring the development of osteoporosis in male Sprague-Dawley rats.

    Methods

    Eight rats were gastrectomized and eight rats were sham operated. Femurs, tibias, and tails were prepared, and CMT scans with spatial resolutions of 5–500 μm were made. Bone diameters, bone areas, and moments of inertia were determined from the CMT scans. Optimal slice position and the need for spatial resolution and energy optimization for future in vivo applications were investigated.

    Results

    Gastrectomy caused dramatic changes in the bone architecture of the tibia and the femur. The main features were vacuolization of the bone and reduced amounts of compact bone. Although the outer diameters of tubular bones (femur and tibia) were largely unaffected, their inner diameters were greatly increased following gastrectomy. Relative bone area and moment of inertia were greatly reduced. The optimal photon energy was 12 keV.

    Conclusion

    It is possible to monitor gastrectomy-evoked changes in bone morphology at various sites in rats using CMT scanning. The changes are suggestive of osteoporosis. By optimizing the energy spectrum and spatial resolution, as well as choosing the proper slice position, it should be possible to keep absorbed doses low enough to avoid acute radiation injury in repeated in vivo measurements.

    Keywords
    Computed microtomography scanning, gastrectomy, osteoporosis, bone architecture, Sprague-Dawley rats
    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-13564 (URN)10.1016/S1076-6332(05)80487-8 (DOI)
    Available from: 2001-02-20 Created: 2001-02-20 Last updated: 2015-03-20
    2. A theoretical model for determination of the optimal irradiation conditions for computerised tomography
    Open this publication in new window or tab >>A theoretical model for determination of the optimal irradiation conditions for computerised tomography
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    1995 (English)In: Insight (Northampton), ISSN 1354-2575, E-ISSN 1754-4904, Vol. 37, no 12, p. 978-985Article in journal (Refereed) Published
    Abstract [en]

    Image quality in Computerised Tomography (CT) depends strongly on the quality of the CT-projection data. These depend on sample composition and geometry, contrasting details within the sample and the equipment used, i.e. X-ray spectra, filtration, detector response and geometry. This paper focuses on the problem of selecting the optimal physical parameters to maximise the signal-to-noise in CT projection data (SNRCT) between a contrasting detail and the surrounding sample for CT-scanners equipped with poly-energetic X-ray sources (conventional X-ray tubes) and energy-integrating detector systems (image intensifier and optical video chain). The work includes the derivation and verification ofa theoretical model for SNRCT which can be used for predicting the optimal physical parameters for specific imaging tasks. It is shown that simplified calculations valid for mono-energetic X-ray sources and/or photon counting detectors do not correctly predict the optimal settings. This study also includes measurements of the actual X-ray source and photon transport Monte Carlo simulations of the response of the detector system.

    Keywords
    Non destructive test ; Optimization ; Tomography ; Image quality ; Filtration ; Experimental study ; Optical method ; X ray irradiation ; Verification ; Measurement method ; Numerical method ; Numerical convergence
    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-13565 (URN)
    Available from: 2001-02-20 Created: 2001-02-20 Last updated: 2017-12-13
    3. Maximising the signal-to-noise ratio in computerised tomography data using robust design
    Open this publication in new window or tab >>Maximising the signal-to-noise ratio in computerised tomography data using robust design
    1996 (English)In: Insight (Northampton), ISSN 1354-2575, E-ISSN 1754-4904, Vol. 38, no 2, p. 112-117Article in journal (Refereed) Published
    Abstract [en]

    Image quality in Computerised Tomography (CT) depends strongly on the quality of the CT-projection data, which vary with the imaged sample and the equipment used. The objective has been to find a setting of the CT-scanner Control Factors (CF) maximising the signal-to-noise ratio in CT projection data (SNRCT) of a contrasting detail (for example a defect) and a surrounding cylindrical sample, and to present a general optimisation methodology. An optimisation case study was carried out, valid for a CT-scanner equipped with a polyenergetic X-ray source (conventional) with tungsten target and a partially energy-integrating detector system (image intensifier and optical video chain), with and without consideration qf the exposure limits associated with the microfocal X-ray source used. The CF of interest were tube potential, exposure (product of tube current and exposure time), material and thickness of the primary filter, optical aperture and attenuation equalising filter design. The settings yielding the highest values of SNRCT were found using thick filter of high atomic number, small iris and use of an X-ray attenuation equalisation filter design. The exposure limits make the CF interdependent, yielding another optimal setting. The CF setting was also found to be independent of the contrasting detail, in the particular case study.

    Keywords
    Non destructive test ; Tomography ; Signal to noise ratio ; Image quality ; Scanner ; Signal analysis ; X ray
    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-13566 (URN)
    Available from: 2001-02-20 Created: 2001-02-20 Last updated: 2017-12-13
    4. Absorbed dose aspects on in vivo microtomography on small experimental animals
    Open this publication in new window or tab >>Absorbed dose aspects on in vivo microtomography on small experimental animals
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    2001 (English)In: Journal of Bone and Mineral Research, ISSN 0884-0431, E-ISSN 1523-4681Article in journal (Refereed) Submitted
    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-13567 (URN)
    Available from: 2001-02-20 Created: 2001-02-20 Last updated: 2017-12-13
    5. Bone mineral density and bone structure parameters as predictors of bone strength: an analysis using computerized microtomography and gastrectomy-induced osteopenia in the rat
    Open this publication in new window or tab >>Bone mineral density and bone structure parameters as predictors of bone strength: an analysis using computerized microtomography and gastrectomy-induced osteopenia in the rat
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    2000 (English)In: Journal of Biomechanics, ISSN 0021-9290, Vol. 33, no 3, p. 289-297Article in journal (Refereed) Published
    Abstract [en]

    In this study the relationships of bone mineral density (BMD) and bone structure parameters calculated from 2D microtomography images to bone strength were investigated. Femurs from 21 male Sprague Dawley rats were subjected to dual-energy X-ray absorptiometry, computerized microtomography (CμT) and either three-point cantilever bending (femoral shaft) or two-point bending compression (femoral neck). Gastrectomy was performed on 12 animals and 9 were sham operated. From the tomograms bone structure analysis was performed using a software routine based on grey level run-length method. Correlations of BMD and bone structure parameters to mechanical parameters were investigated as were differences between the gastrectomized and the control samples. The reductions of BMD between the groups were 21 and 27% in the femoral neck and shaft, respectively. For the shaft, the correlations of BMD to all mechanical parameters were significant and BMD was a consistent predictor of bone strength for cortical bone. However, in the femoral neck where cancellous bone predominates, BMD was weakly correlated only to deflection. A significant correlation between trabecular thickness and neck bone strength was found. Hence, compared to trabecular thickness, BMD was of limited value in predicting bone strength in the femoral neck.

    Keywords
    Computerised microtomography, Bone structure, Bone strength, Bone mineral density, Osteopenia
    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-13568 (URN)10.1016/S0021-9290(99)00181-5 (DOI)
    Available from: 2001-02-20 Created: 2001-02-20 Last updated: 2015-03-20
  • 263.
    Stenström, Mats
    et al.
    Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Linköping University, Faculty of Health Sciences.
    Olander, Birger
    Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Linköping University, Faculty of Health Sciences.
    Carlsson, Carl A.
    Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Linköping University, Faculty of Health Sciences.
    Alm Carlsson, Gudrun
    Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics.
    Håkanson, Rolf
    Department of Pharmacology, University of Lund, Lund, Sweden.
    Methodologic aspects of computed microtomography to monitor the development of osteoporosis in gastrectomized rats1995In: Academic Radiology, ISSN 1076-6332, Vol. 2, no 9, p. 785-791Article in journal (Refereed)
    Abstract [en]

    Rationale and Objectives

    We investigated the methodologic development of computed microtomography (CMT) for monitoring the development of osteoporosis in male Sprague-Dawley rats.

    Methods

    Eight rats were gastrectomized and eight rats were sham operated. Femurs, tibias, and tails were prepared, and CMT scans with spatial resolutions of 5–500 μm were made. Bone diameters, bone areas, and moments of inertia were determined from the CMT scans. Optimal slice position and the need for spatial resolution and energy optimization for future in vivo applications were investigated.

    Results

    Gastrectomy caused dramatic changes in the bone architecture of the tibia and the femur. The main features were vacuolization of the bone and reduced amounts of compact bone. Although the outer diameters of tubular bones (femur and tibia) were largely unaffected, their inner diameters were greatly increased following gastrectomy. Relative bone area and moment of inertia were greatly reduced. The optimal photon energy was 12 keV.

    Conclusion

    It is possible to monitor gastrectomy-evoked changes in bone morphology at various sites in rats using CMT scanning. The changes are suggestive of osteoporosis. By optimizing the energy spectrum and spatial resolution, as well as choosing the proper slice position, it should be possible to keep absorbed doses low enough to avoid acute radiation injury in repeated in vivo measurements.

  • 264.
    Stenström, Mats
    et al.
    Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Linköping University, Faculty of Health Sciences.
    Olander, Birger
    Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Linköping University, Faculty of Health Sciences.
    Lehto-Axtelius, Daisy
    Department of Radiology, Centre for Oral Health, Malmö University, Sweden.
    Madsen, Jan Erik
    Institute for Surgical Research, Rikshospitalet, Oslo, Norway.
    Nordsletten, Lars
    Institute for Surgical Research, Rikshospitalet, Oslo, Norway.
    Alm Carlsson, Gudrun
    Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics.
    Bone mineral density and bone structure parameters as predictors of bone strength: an analysis using computerized microtomography and gastrectomy-induced osteopenia in the rat2000In: Journal of Biomechanics, ISSN 0021-9290, Vol. 33, no 3, p. 289-297Article in journal (Refereed)
    Abstract [en]

    In this study the relationships of bone mineral density (BMD) and bone structure parameters calculated from 2D microtomography images to bone strength were investigated. Femurs from 21 male Sprague Dawley rats were subjected to dual-energy X-ray absorptiometry, computerized microtomography (CμT) and either three-point cantilever bending (femoral shaft) or two-point bending compression (femoral neck). Gastrectomy was performed on 12 animals and 9 were sham operated. From the tomograms bone structure analysis was performed using a software routine based on grey level run-length method. Correlations of BMD and bone structure parameters to mechanical parameters were investigated as were differences between the gastrectomized and the control samples. The reductions of BMD between the groups were 21 and 27% in the femoral neck and shaft, respectively. For the shaft, the correlations of BMD to all mechanical parameters were significant and BMD was a consistent predictor of bone strength for cortical bone. However, in the femoral neck where cancellous bone predominates, BMD was weakly correlated only to deflection. A significant correlation between trabecular thickness and neck bone strength was found. Hence, compared to trabecular thickness, BMD was of limited value in predicting bone strength in the femoral neck.

  • 265.
    Stenström, Mats
    et al.
    Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Linköping University, Faculty of Health Sciences.
    Olander, Birger
    Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Linköping University, Faculty of Health Sciences.
    Söderberg, Jonas
    Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Linköping University, Faculty of Health Sciences.
    Sandborg, Michael
    Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Linköping University, Faculty of Health Sciences.
    Alm Carlsson, Gudrun
    Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Linköping University, Faculty of Health Sciences.
    Absorbed dose aspects on in vivo microtomography on small experimental animals2001In: Journal of Bone and Mineral Research, ISSN 0884-0431, E-ISSN 1523-4681Article in journal (Refereed)
  • 266.
    Svalkvist, Angelica
    et al.
    University of Gothenburg, Sweden Sahlgrens University Hospital, Sweden .
    Allansdotter Johnsson, Ase
    University of Gothenburg, Sweden Sahlgrens University Hospital, Sweden .
    Vikgren, Jenny
    University of Gothenburg, Sweden Sahlgrens University Hospital, Sweden .
    Hakansson, Markus
    University of Gothenburg, Sweden .
    Ullman, Gustaf
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Boijsen, Marianne
    University of Gothenburg, Sweden Sahlgrens University Hospital, Sweden .
    Fisichella, Valeria
    University of Gothenburg, Sweden Sahlgrens University Hospital, Sweden .
    Flinck, Agneta
    University of Gothenburg, Sweden Sahlgrens University Hospital, Sweden .
    Molnar, David
    Sahlgrens University Hospital, Sweden .
    Mansson, Lars Gunnar
    University of Gothenburg, Sweden Sahlgrens University Hospital, Sweden .
    Bath, Magnus
    University of Gothenburg, Sweden Sahlgrens University Hospital, Sweden .
    Evaluation of an improved method of simulating lung nodules in chest tomosynthesis2012In: Acta Radiologica, ISSN 0284-1851, E-ISSN 1600-0455, Vol. 53, no 8, p. 874-884Article in journal (Refereed)
    Abstract [en]

    Background: Simulated pathology is a valuable complement to clinical images in studies aiming at evaluating an imaging technique. In order for a study using simulated pathology to be valid, it is important that the simulated pathology in a realistic way reflect the characteristics of real pathology. less thanbrgreater than less thanbrgreater thanPurpose: To perform a thorough evaluation of a nodule simulation method for chest tomosynthesis, comparing the detection rate and appearance of the artificial nodules with those of real nodules in an observer performance experiment. less thanbrgreater than less thanbrgreater thanMaterial and Methods: A cohort consisting of 64 patients, 38 patients with a total of 129 identified pulmonary nodules and 26 patients without identified pulmonary nodules, was used in the study. Simulated nodules, matching the real clinically found pulmonary nodules by size, attenuation, and location, were created and randomly inserted into the tomosynthesis section images of the patients. Three thoracic radiologists and one radiology resident reviewed the images in an observer performance study divided into two parts. The first part included nodule detection and the second part included rating of the visual appearance of the nodules. The results were evaluated using a modified receiver-operating characteristic (ROC) analysis. less thanbrgreater than less thanbrgreater thanResults: The sensitivities for real and simulated nodules were comparable, as the area under the modified ROC curve (AUC) was close to 0.5 for all observers (range, 0.43-0.55). Even though the ratings of visual appearance for real and simulated nodules overlapped considerably, the statistical analysis revealed that the observers to were able to separate simulated nodules from real nodules (AUC values range 0.70-0.74). less thanbrgreater than less thanbrgreater thanConclusion: The simulation method can be used to create artificial lung nodules that have similar detectability as real nodules in chest tomosynthesis, although experienced thoracic radiologists may be able to distinguish them from real nodules.

  • 267.
    Svalkvist, Angelica
    et al.
    University of Gothenburg.
    Hakansson, Markus
    University of Gothenburg.
    Ullman, Gustaf
    Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Linköping University, Faculty of Health Sciences.
    Bath, Magnus
    University of Gothenburg.
    Simulation of lung nodules in chest tomosynthesis2010In: RADIATION PROTECTION DOSIMETRY, ISSN 0144-8420, Vol. 139, no 1-3, p. 130-139Article in journal (Refereed)
    Abstract [en]

    The aim of the present work was to develop an adequate method for simulating lung nodules in clinical chest tomosynthesis images. Based on the visual appearance of real nodules, artificial, three-dimensional nodules with irregular shape and surface structure were created using an approach of combining spheres of different sizes and central points. The nodules were virtually positioned at the desired locations inside the patient and by using the known geometry of the tomosynthesis acquisition, the radiation emitted from the focal spot, passing through the nodule and reaching the detector could be simulated. The created nodules were thereby projected into raw-data tomosynthesis projection images before reconstruction of the tomosynthesis section images. The focal spot size, signal spread in the detector, scattered radiation, patient motion and existing anatomy at the location of the nodule were taken into account in the simulations. It was found that the blurring caused by the modulation transfer function and the patient motion overshadows the effects of a finite focal spot and aliasing and also obscures the surface structure of the nodules, which provides an opportunity to simplify the simulations and decrease the simulation times. Also, the limited in-depth resolution of the reconstructed tomosynthesis section images reduces the necessity to take details of the anatomical structures at the location of the inserted nodule into account.

  • 268.
    Svalkvist, Angelica
    et al.
    Dept. of Radiation Physics, Sahlgrenska Academy at University of Gothenburg, Gothenburg, Sweden.
    Ullman, Gustaf
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences. Department of Cell and Molecular Biology, Uppsala University, Uppsala, Sweden.
    Håkansson, Markus
    Dept. of Radiation Physics, Sahlgrenska Academy at University of Gothenburg, Gothenburg, Sweden and Dept. of Diagnostic Radiology, Södra Älvsborgs Sjukhus, Sahlgrenska University Hospital, Gothenburg, Sweden.
    Dance, David R.
    NCCPM, Royal Surrey County Hospital, Guildford , UK.
    Sandborg, Michael
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Department of Biomedical Engineering, Center for Medical Image Science and Visualization. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics.
    Alm Carlsson, Gudrun
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics.
    Båth, Magnus
    Dept. of Radiation Physics, Sahlgrenska Academy at University of Gothenburg, Gothenburg, Sweden and fDept. of Medical Physics and Biomedical Engineering, Sahlgrenska University Hospital, Gothenburg, Sweden.
    Investigation of the effect of varying scatter-to-primary ratios on nodule contrast in chest tomosynthesis2011In: Medical Imaging 2011: Physics of Medical Imaging / [ed] Norbert J. Pelc; Ehsan Samei; Robert M. Nishikawa, SPIE - International Society for Optical Engineering, 2011, p. 79615Y-1-79615Y-10Conference paper (Other academic)
    Abstract [en]

    The primary aim of the present work was to analyze the effects of varying scatter-to-primary ratios on the appearance of simulated nodules in chest tomosynthesis section images. Monte Carlo simulations of the chest tomosynthesis system GE Definium 8000 VolumeRAD (GE Healthcare, Chalfont St. Giles, UK) were used to investigate the variation of scatter-to-primary ratios between different angular projections. The simulations were based on a voxel phantom created from CT images of an anthropomorphic chest phantom. An artificial nodule was inserted at 80 different positions in the simulated phantom images, using five different approaches for the scatter-to-primary ratios in the insertion process. One approach included individual determination of the scatter-to primary-ratio for each projection image and nodule location, while the other four approaches were using mean value, median value and zero degree projection value of the scatter-to-primary ratios at each nodule position as well as using a constant scatter-to-primary ratio of 0.5 for all nodule positions. The results indicate that the scatter-to-primary ratios vary up to a factor of 10 between the different angular tomosynthesis projections (±15°). However, the error in the resulting nodule contrast introduced by not taking all variations into account is in general smaller than 10 %.

  • 269.
    Söderberg, Jonas
    Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Linköping University, Faculty of Health Sciences.
    Dosimetry and radiation quality in fast-neutron radiation therapy: A study of radiation quality and basic dosimetric properties of fast-neutrons for external beam radiotherapy and problems associated with corrections of measured charged particle cross-sections2007Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The dosimetric properties of fast-neutron beams with energies ≤80 MeV were explored using Monte Carlo techniques. Taking into account transport of all relevant types of released charged particles (electrons, protons, deuterons, tritons, 3He and α particles) pencil-beam dose distributions were derived and used to calculate absorbed dose distributions. Broad-beam depth doses in phantoms of different materials were calculated and compared and the scaling factors required for converting absorbed dose in one material to absorbed dose in another derived. The scaling factors were in good agreement with available published data and show that water is a good substitute for soft tissue even at neutron energies as high as 80 MeV. The inherent penumbra and the fraction of absorbed dose due to photon interactions were also studied, and found to be consistent with measured values reported in the literature.

    Treatment planning in fast-neutron therapy is commonly performed using dose calculation algorithms designed for photon beam therapy. When applied to neutron beams, these algorithms have limitations arising from the physical models used. Monte Carlo derived neutron pencil-beam kernels were parameterized and implemented in the photon dose calculation algorithms of the TMS (MDS Nordion) treatment planning system. It was shown that these algorithms yield good results in homogeneous water media. However, the method used to calculate heterogeneity corrections in the photon dose calculation algorithm did not yield correct results for neutron beams in heterogeneous media.

    To achieve results with adequate accuracy using Monte Carlo simulations, fundamental cross-section data are needed. Neutron cross-sections are still not sufficiently well known. At the The Svedberg Laboratory in Uppsala, Sweden, an experimental facility has been designed to measure neutron-induced charged-particle production cross-sections for (n,xp), (n,xd), (n,xt), (n,x3He) and (n,xα) reactions at neutron energies up to 100 MeV. Depending on neutron energy, these generated particles account for up to 90% of the absorbed dose. In experimental determination of the cross-sections, measured data have to be corrected for the energies lost by the charged particles before leaving the target in which they were generated. To correct for the energy-losses, a computational code (CRAWL) was developed. It uses a stripping method. With the limitation of reduced energy resolution, spectra derived using CRAWL compares well with those derived using other methods.

    In fast-neutron therapy, the relative biological effectiveness (RBE) varies from 1.5 to 5, depending on neutron energy, dose level and biological end-point. LET and other physical quantities, developed within the field of microdosimetry over the past couple of decades, have been used to describe RBE variations between different fast-neutron beams as well as within a neutron irradiated body. In this work, a Monte Carlo code (SHIELD-HIT) capable of transporting all charged particles contributing to absorbed dose, was used to calculate energy-differential charged particle spectra. Using these spectra, values of the RBE related quantities LD, γD, γ* and R were derived and studied as function of neutron energy, phantom material and position in a phantom. Reasonable agreement with measured data in the literature was found and indicates that the quantities may be used to predict RBE variations in an arbitrary fast-neutron beam.

    List of papers
    1. Correction of measured charged-particle spectra for energy losses in the target: A comparison of three methods
    Open this publication in new window or tab >>Correction of measured charged-particle spectra for energy losses in the target: A comparison of three methods
    2002 (English)In: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, ISSN 0168-583X, E-ISSN 1872-9584, Vol. 195, no 3-4, p. 426-434Article in journal (Refereed) Published
    Abstract [en]

    The experimental facility, MEDLEY, at the The Svedberg Laboratory in Uppsala, has been constructed to measure neutron-induced charged-particle production cross-sections for (n, xp), (n, xd), (n, xt), (n, x3He) and (n, xα) reactions at neutron energies up to 100 MeV. Corrections for the energy loss of the charged particles in the target are needed in these measurements, as well as for loss of particles. Different approaches have been used in the literature to solve this problem. In this work, a stripping method is developed, which is compared with other methods developed by Rezentes et al. and Slypen et al. The results obtained using the three codes are similar and they could all be used for correction of experimental charged-particle spectra. Statistical fluctuations in the measured spectra cause problems independent of the applied technique, but the way to handle it differs in the three codes.

    Keywords
    Neutron, Cross-section, Charged particle, Energy-loss corrections
    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-14359 (URN)10.1016/S0168-583X(02)01090-X (DOI)000178915500023 ()
    Available from: 2007-03-22 Created: 2007-03-22 Last updated: 2017-12-13
    2. Fast neutron absorbed dose distributions in the energy range 0.5-80 MeV: a Monte Carlo study
    Open this publication in new window or tab >>Fast neutron absorbed dose distributions in the energy range 0.5-80 MeV: a Monte Carlo study
    2000 (English)In: Physics in Medicine and Biology, ISSN 0031-9155, E-ISSN 1361-6560, Vol. 45, no 10, p. 2987-3007Article in journal (Refereed) Published
    Abstract [en]

    Neutron pencil-beam absorbed dose distributions in phantoms of bone, ICRU soft tissue, muscle, adipose and the tissue substitutes water, A-150 (plastic) and PMMA (acrylic) have been calculated using the Monte Carlo code FLUKA in the energy range 0.5 to 80 MeV. For neutrons of energies ≤20 MeV, the results were compared to those obtained using the Monte Carlo code MCNP4B. Broad-beam depth doses and lateral dose distributions were derived. Broad-beam dose distributions in various materials were compared using two kinds of scaling factor: a depth-scaling factor and a dose-scaling factor. Build-up factors due to scattered neutrons and photons were derived and the appropriate choice of phantom material for determining dose distributions in soft tissue examined. Water was found to be a good substitute for soft tissue even at neutron energies as high as 80 MeV. The relative absorbed doses due to photons ranged from 2% to 15% for neutron energies 10-80 MeV depending on phantom material and depth. For neutron energies below 10 MeV the depth dose distributions derived with MCNP4B and FLUKA differed significantly, the difference being probably due to the use of multigroup transport of low energy (<19.6 MeV) neutrons in FLUKA. Agreement improved with increasing neutron energies up to 20 MeV. At energies >20 MeV, MCNP4B fails to describe dose build-up at the phantom interface and penumbra at the edge of the beam because it does not transport secondary charged particles. The penumbra width, defined as the distance between the 80% and 20% iso-dose levels at 5 cm depth and for a 10×10 cm2 field, was between 0.9 mm and 7.2 mm for neutron energies 10-80 MeV.

    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-14360 (URN)10.1088/0031-9155/45/10/317 (DOI)000089865300017 ()
    Available from: 2007-03-22 Created: 2007-03-22 Last updated: 2017-12-13
    3. Monte Carlo evaluation of a photon pencil kernel algorithm applied to fast neutron therapy treatment planning
    Open this publication in new window or tab >>Monte Carlo evaluation of a photon pencil kernel algorithm applied to fast neutron therapy treatment planning
    2003 (English)In: Physics in Medicine and Biology, ISSN 0031-9155, Vol. 48, no 20, p. 3327-3344Article in journal (Refereed) Published
    Abstract [en]

    When dedicated software is lacking, treatment planning for fast neutron therapy is sometimes performed using dose calculation algorithms designed for photon beam therapy. In this work Monte Carlo derived neutron pencil kernels in water were parametrized using the photon dose algorithm implemented in the Nucletron TMS (treatment management system) treatment planning system. A rectangular fast-neutron fluence spectrum with energies 0–40 MeV (resembling a polyethylene filtered p(41)+ Be spectrum) was used. Central axis depth doses and lateral dose distributions were calculated and compared with the corresponding dose distributions from Monte Carlo calculations for homogeneous water and heterogeneous slab phantoms. All absorbed doses were normalized to the reference dose at 10 cm depth for a field of radius 5.6 cm in a 30 × 40 × 20 cm3 water test phantom. Agreement to within 7% was found in both the lateral and the depth dose distributions. The deviations could be explained as due to differences in size between the test phantom and that used in deriving the pencil kernel (radius 200 cm, thickness 50 cm). In the heterogeneous phantom, the TMS, with a directly applied neutron pencil kernel, and Monte Carlo calculated absorbed doses agree approximately for muscle but show large deviations for media such as adipose or bone. For the latter media, agreement was substantially improved by correcting the absorbed doses calculated in TMS with the neutron kerma factor ratio and the stopping power ratio between tissue and water. The multipurpose Monte Carlo code FLUKA was used both in calculating the pencil kernel and in direct calculations of absorbed dose in the phantom.

    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-14361 (URN)10.1088/0031-9155/48/20/005 (DOI)
    Available from: 2007-03-22 Created: 2007-03-22 Last updated: 2015-03-20
    4. RBE related quantities in fast-neutron therapy beams derived using Monte Carlo calculated charged particle spectra
    Open this publication in new window or tab >>RBE related quantities in fast-neutron therapy beams derived using Monte Carlo calculated charged particle spectra
    Show others...
    Manuscript (Other academic)
    Identifiers
    urn:nbn:se:liu:diva-14362 (URN)
    Available from: 2007-03-22 Created: 2007-03-22 Last updated: 2010-01-13
  • 270.
    Söderberg, Jonas
    et al.
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Alm Carlsson, Gudrun
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics.
    Fast neutron absorbed dose distributions in the energy range 0.5-80 MeV: a Monte Carlo study2000In: Physics in Medicine and Biology, ISSN 0031-9155, E-ISSN 1361-6560, Vol. 45, no 10, p. 2987-3007Article in journal (Refereed)
    Abstract [en]

    Neutron pencil-beam absorbed dose distributions in phantoms of bone, ICRU soft tissue, muscle, adipose and the tissue substitutes water, A-150 (plastic) and PMMA (acrylic) have been calculated using the Monte Carlo code FLUKA in the energy range 0.5 to 80 MeV. For neutrons of energies ≤20 MeV, the results were compared to those obtained using the Monte Carlo code MCNP4B. Broad-beam depth doses and lateral dose distributions were derived. Broad-beam dose distributions in various materials were compared using two kinds of scaling factor: a depth-scaling factor and a dose-scaling factor. Build-up factors due to scattered neutrons and photons were derived and the appropriate choice of phantom material for determining dose distributions in soft tissue examined. Water was found to be a good substitute for soft tissue even at neutron energies as high as 80 MeV. The relative absorbed doses due to photons ranged from 2% to 15% for neutron energies 10-80 MeV depending on phantom material and depth. For neutron energies below 10 MeV the depth dose distributions derived with MCNP4B and FLUKA differed significantly, the difference being probably due to the use of multigroup transport of low energy (<19.6 MeV) neutrons in FLUKA. Agreement improved with increasing neutron energies up to 20 MeV. At energies >20 MeV, MCNP4B fails to describe dose build-up at the phantom interface and penumbra at the edge of the beam because it does not transport secondary charged particles. The penumbra width, defined as the distance between the 80% and 20% iso-dose levels at 5 cm depth and for a 10×10 cm2 field, was between 0.9 mm and 7.2 mm for neutron energies 10-80 MeV.

  • 271.
    Söderberg, Jonas
    et al.
    Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Linköping University, Faculty of Health Sciences.
    Alm Carlsson, Gudrun
    Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics.
    Ahnesjö, Anders
    Nucletron Scandinavia AB, Uppsala, Sweden.
    Monte Carlo evaluation of a photon pencil kernel algorithm applied to fast neutron therapy treatment planning2003In: Physics in Medicine and Biology, ISSN 0031-9155, Vol. 48, no 20, p. 3327-3344Article in journal (Refereed)
    Abstract [en]

    When dedicated software is lacking, treatment planning for fast neutron therapy is sometimes performed using dose calculation algorithms designed for photon beam therapy. In this work Monte Carlo derived neutron pencil kernels in water were parametrized using the photon dose algorithm implemented in the Nucletron TMS (treatment management system) treatment planning system. A rectangular fast-neutron fluence spectrum with energies 0–40 MeV (resembling a polyethylene filtered p(41)+ Be spectrum) was used. Central axis depth doses and lateral dose distributions were calculated and compared with the corresponding dose distributions from Monte Carlo calculations for homogeneous water and heterogeneous slab phantoms. All absorbed doses were normalized to the reference dose at 10 cm depth for a field of radius 5.6 cm in a 30 × 40 × 20 cm3 water test phantom. Agreement to within 7% was found in both the lateral and the depth dose distributions. The deviations could be explained as due to differences in size between the test phantom and that used in deriving the pencil kernel (radius 200 cm, thickness 50 cm). In the heterogeneous phantom, the TMS, with a directly applied neutron pencil kernel, and Monte Carlo calculated absorbed doses agree approximately for muscle but show large deviations for media such as adipose or bone. For the latter media, agreement was substantially improved by correcting the absorbed doses calculated in TMS with the neutron kerma factor ratio and the stopping power ratio between tissue and water. The multipurpose Monte Carlo code FLUKA was used both in calculating the pencil kernel and in direct calculations of absorbed dose in the phantom.

  • 272.
    Söderberg, Jonas
    et al.
    Linköping University, Department of Medicine and Care, Radio Physics. Linköping University, Faculty of Health Sciences.
    Dangtip, Somsak
    Department of Neutron Research, Uppsala University, Uppsala, Sweden.
    Alm Carlsson, Gudrun
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics.
    Olsson, Nils
    Department of Neutron Research, Uppsala University, Uppsala, Sweden.
    Correction of measured charged-particle spectra for energy losses in the target: A comparison of three methods2002In: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, ISSN 0168-583X, E-ISSN 1872-9584, Vol. 195, no 3-4, p. 426-434Article in journal (Refereed)
    Abstract [en]

    The experimental facility, MEDLEY, at the The Svedberg Laboratory in Uppsala, has been constructed to measure neutron-induced charged-particle production cross-sections for (n, xp), (n, xd), (n, xt), (n, x3He) and (n, xα) reactions at neutron energies up to 100 MeV. Corrections for the energy loss of the charged particles in the target are needed in these measurements, as well as for loss of particles. Different approaches have been used in the literature to solve this problem. In this work, a stripping method is developed, which is compared with other methods developed by Rezentes et al. and Slypen et al. The results obtained using the three codes are similar and they could all be used for correction of experimental charged-particle spectra. Statistical fluctuations in the measured spectra cause problems independent of the applied technique, but the way to handle it differs in the three codes.

  • 273.
    Söderfeldt, Birgitta
    et al.
    Karolinska institutet.
    Ragnehed, Mattias
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medicine and Health Sciences, Radiation Physics. Östergötlands Läns Landsting, Centre for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics UHL. Linköping University, Faculty of Health Sciences.
    Håkansson, Irene
    Östergötlands Läns Landsting, Sinnescentrum. Linköping University, Department of Clinical and Experimental Medicine. Linköping University, Faculty of Health Sciences.
    Lundberg, Peter
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medicine and Health Sciences, Radiation Physics. Linköping University, Department of Medicine and Health Sciences, Radiology. Östergötlands Läns Landsting, Centre for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics UHL. Östergötlands Läns Landsting, Centre for Diagnostics, Department of Radiology in Linköping. Linköping University, Faculty of Health Sciences.
    Nilsson, M
    Ahlner, Johan
    Östergötlands Läns Landsting, Heart and Medicine Centre. Östergötlands Läns Landsting, Heart and Medicine Centre, Department of Endocrinology and Gastroenterology UHL. Linköping University, Department of Medicine and Health Sciences, Clinical Pharmacology. Linköping University, Faculty of Health Sciences.
    Engström, Maria
    Linköping University, Department of Medicine and Health Sciences, Radiology. Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Faculty of Health Sciences.
    Influence of Diazepam on Clinically Designed fMRI2006Conference paper (Other academic)
  • 274.
    Tapiovaara, Markku
    et al.
    Finnish Centre for Radiat. & Nucl. Safety.
    Sandborg, Michael
    Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Linköping University, Center for Medical Image Science and Visualization, CMIV. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics. Linköping University, Faculty of Health Sciences.
    Evaluation of image quality in fluoroscopy by measurements and Monte Carlo calculations1995In: Physics in Medicine and Biology, ISSN 0031-9155, E-ISSN 1361-6560, Vol. 40, no 4, p. 589-607Article in journal (Refereed)
    Abstract [en]

    The authors have studied image quality in fluoroscopy, as related to the detectability of low-contrast iodine or acrylic (PMMA) details added to a homogeneous 20 cm thick PMMA phantom, by experimental measurements of the signal-to-noise ratio (SNR) and by Monte Carlo calculation. The agreement between the measured and calculated SNR at equal absorbed dose in the phantom showed that the imaging performance of X-ray image intensifier (XRII) based fluoroscopic systems is well understood and can be mainly accounted for by X-ray attenuation in the phantom and the detail, and by the interaction statistics of primary and secondary (scattered) X-ray quanta in the input phosphor of the XRII. The electronic noise sources in the video chain bad only a small effect on the detectability of the details studied here. The optimal X-ray tube potential was 50-60 kV for detecting the low-contrast iodine detail in the phantom, and 70-100 kV for detecting the thin PMMA detail. For the task of detecting the iodine detail the use of a fibre-interspaced antiscatter grid improved the dose-to-information conversion efficiency of the imaging system by a factor of 2.2 as compared to imaging without the grid, and additional filtering of the X-ray beam by 0.25 mm Cu increased the efficiency by a factor of 1.6. Monte Carlo results were further used to estimate the potential of increasing the dose-to-information conversion efficiency by imaging system design changes. For the detection task of a static, low-contrast, low-spatial-frequency iodine contrast material detail embedded in a 20 cm thick soft-tissue phantom, the greatest contributions for further improvement could be achieved by improved antiscatter devices, X-ray spectrum modification, and by decreasing the absorption in the material layers in front of the CsI phosphor of the XRII. Contrary to this, no significant efficiency increase could be obtained by increasing the CsI phosphor coating thickness from the present value of 180 mg cm-2, or by changes in the video chain characteristics. The maximum potential of efficiency improvement is a factor of 6.3 when compared to the reference fluoroscopy system operated at 60 kV with 2.7 mm Al primary beam filtration, and a factor of 3.9 when compared to the reference system at 50 kV with the primary beam filtration added by 0.25 mm Cu.

  • 275.
    Thomson, R M.
    et al.
    Carleton University, Canada .
    Carlsson Tedgren, Åsa
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics UHL.
    Williamson, J F.
    Virginia Commonwealth University, VA USA .
    On the biological basis for competing macroscopic dose descriptors for kilovoltage dosimetry: cellular dosimetry for brachytherapy and diagnostic radiology2013In: Physics in Medicine and Biology, ISSN 0031-9155, E-ISSN 1361-6560, Vol. 58, no 4, p. 1123-1150Article in journal (Refereed)
    Abstract [en]

    The purpose of this work is to investigate how alternative macroscopic dose descriptors track absorbed dose to biologically relevant subcellular targets via Monte Carlo (MC) analysis of cellular models for a variety of cancerous and normal soft tissues for kilovoltage radiation. The relative mass distributions of water, light inorganic elements, and protein components of nuclear and cytoplasm compartments for various tissues are determined from a literature review. These data are used to develop representative cell models to demonstrate the range of mass elemental compositions of these subcellular structures encountered in the literature from which radiological quantities (energy absorption and attenuation coefficients; stopping powers) are computed. Using representative models of cell clusters, doses to subcellular targets are computed using MC simulation for photon sources of energies between 20 and 370 keV and are compared to bulk medium dose descriptors. It is found that cells contain significant and varying mass fractions of protein and inorganic elements, leading to variations in mass energy absorption coefficients for cytoplasm and nuclear media as large as 10% compared to water for sub-50 keV photons. Doses to subcellular structures vary by as much as 23% compared to doses to the corresponding average bulk medium or to small water cavities embedded in the bulk medium. Relationships between cellular target doses and doses to the bulk medium or to a small water cavity embedded in the bulk medium are sensitive to source energy and cell morphology, particularly for lower energy sources, e. g., low energy brachytherapy (andlt;50 keV). Results suggest that cells in cancerous and normal soft tissues are generally not radiologically equivalent to either water or the corresponding average bulk tissue. For kilovoltage photon sources, neither dose to bulk medium nor dose to water quantitatively tracks energy imparted to biologically relevant subcellular targets for the range of cellular morphologies and tissues considered.

  • 276.
    Tisell, Anders
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics UHL.
    The Non-Invasive Brain Biopsy: Implementation and Application of Quantitative Magnetic Resonance Spectroscopy on Healthy and Diseased Human Brain2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Introduction: In this thesis, one of the major objectives was to implement a method for (absolute) quantitative magnetic resonance spectroscopy (qMRS) of the human brain, intended for clinical use. The implemented method was based on standard spatially selective MRS sequences. The tissue water was used as an internal reference, which was calibrated using whole brain quantitative magnetic resonance imaging (qMRI). The second objective was to apply the method in clinical neuroimaging investigation, of different disease processes in the human brain.

    Materials and Methods: In total, 158 subjects were included and 507 MRS measurements (330 in white matter and 177 in the thalamus) were acquired.

    In a cross-sectional study of multiple sclerosis (MS), 35 ‘clinically definite MS’ (CDMS) patients were included, of which 15 were atypical CDMS patients with a very low number of white matter lesions (two or fewer), and 20 were typical CDMS patients with white matter lesions (three or more) were included. The metabolite concentrations in normal appearing white matter (NAWM) and the thalamus were assessed using the qMRS method developed in this thesis, and the brain parenchymal fraction (BPF) was calculated from the qMRI data. A cohort of 27 CDMS patients were then treated with Natalizumab and examined both at baseline, and after one year of treatment. Both qMRS and CSF samples for the purpose of assessing intrathecal inflammation were obtained. In addition, the frontal deep white matter (FDWM) and the thalamus were investigated in 20 idiopathic normal pressure hydrocephalus (iNPH) patients using qMRS. Finally, the left thalamus of 14 Kleine-Levin Syndrome (KLS) patients were examined using both qMRS and functional MRI (fMRI) of neurological activation of the left thalamus during a working memory test. Moreover, 63 healthy subjects were included as controls for this work.

    Results: A quantitative MRS method based on water referencing was successfully developed, implemented, and evaluated at 1.5 T. Both healthy subjects and MS patients showed a positive correlation between the concentrations of total Creatine (tCr) and myo Inositol (mIns) and age, and also a negative correlation with BPF were observed. Glutamate and Glutamine (Glx) levels were elevated for all MS patient groups compared to healthy controls. In contrast, lower concentrations of total N-acetyl aspartate and N-acetyl aspartate glutamate (tNA) and higher mIns concentrations in NAWM were only observed in MS patients that had developed white matter lesions. Moreover, the change in concentrations of tCr and total Choline (tCho) in MS patients during Natalizumab-treatment were positively correlated with markers of intrathecal inflammation. The iNPH patients had lower tNA and N-acetyl aspartate (NAA) concentrations in the thalamus compared to the controls. In addition, the NAA concentrations in the left thalamus were inversely correlated to the fMRI activation in the left thalamus during the working memory test in KLS patients.

    Discussion: The calculated calibration factors were in good agreement with the results found in the literature, indicating that the calibration factors were accurate.

    The observed elevated Glx concentration in MS could be due to increased concentrations of glutamate (Glu), which is neurotoxic at high concentrations, thus the elevated Glx could be linked to the clinically observed neurodegeneration in MS both in patients that have developed lesions and in atypical patients that do not develop any (or extremely few) lesions.

    Both tCr and mIns can be used as glia markers, thus the correlations of tCr and mIns concentrations with both age and BPF indicates that the local glia cell density, or tissue fraction, increases with age and atrophy. Moreover, the higher mIns concentrations in the NAWM of MS patients with a substantial white matter lesion load indicate that the glia tissue amount in NAWM is increased in MS patients that develop lesions. NAA is neuronal-specific, thus the lower tNA concentrations indicate that the neurone concentration is lower in the NAWM of MS patients that develop MS lesions. The lack of correlation between tNA with age and BPF in combination with the presence of correlation between tCr and mIns with both age and BPF, might be explained using a model for neurodegeneration. In which, there is a higher neurone loss compared to the glia loss. However, the lost tissue is compensated by compression of the tissue, which keeps the density of neurones more or less constant and the density of glia increased.

    The low concentration levels of the neuronal marker NAA in the thalamus of the iNPH patients indicates that the basal ganglia-thalamic-subcortical frontal circuits are damage or at least strongly modulated in the thalamus.

    The correlation between strong activation in left thalamus during a working memory test with the neuronal marker NAA indicate that the KLS patients that have low neuronal concentration also needed to utilise the working memory circuitry more heavily in order to perform the task as healthy subjects.

    Conclusion: It is possible to use qMRI for accurate and robust determination of qMRS in clinical practice, even at 1.5 T field strength. The tGlx concentration may be an important marker for pathology in the nonlesional white matter of MS-patients. The increased glia and loss of neurones in the NAWM are associated with the formation of white matter lesions.

    List of papers
    1. Procedure for Quantitative 1H Magnetic Resonance Spectroscopy and Tissue Characterization of Human Brain Tissue Based on the Use of Quantitative Magnetic Resonance Imaging
    Open this publication in new window or tab >>Procedure for Quantitative 1H Magnetic Resonance Spectroscopy and Tissue Characterization of Human Brain Tissue Based on the Use of Quantitative Magnetic Resonance Imaging
    2013 (English)In: Magnetic Resonance in Medicine, ISSN 0740-3194, E-ISSN 1522-2594, Vol. 70, no 4, p. 905-915Article in journal (Refereed) Published
    Abstract [en]

    PurposeExisting methods for quantitative magnetic resonance spectroscopy are not widely used for magnetic resonance spectroscopy examinations in clinical practice due to the lengthy and difficult workflow. In this report, we aimed to investigate whether metabolite concentrations show co-variation with relaxation parameters (R-1,R-H2O,R-2,R-H2O), water concentration (C-H2O), and age, using a quantitative magnetic resonance spectroscopy method, which is suitable for a clinical setting. MethodsWe performed 166 single voxel magnetic resonance spectroscopy measurements in the white matter and thalamus in 47 healthy subjects, aged 18-72 years. Whole brain R-1,R-H2O, R-2,R-H2O, and C-H2O maps were determined for each subject using quantitative magnetic resonance imaging. Absolute metabolite concentrations were calculated by calibrating the water-scaled magnetic resonance spectroscopy, using the quantitative magnetic resonance imaging maps of R-1,R-H2O, R-2,R-H2O, and C-H2O. ResultsAbsolute concentrations in white matter of total Creatine and myo-Inositol were correlated with age (total Creatine: 12 4 M/year, P < 0.01; myo-Inositol: 23 +/- 9 M/year, P < 0.05), suggesting a process of increased glia density in aging white matter. Moreover, total Creatine and total N-acetylaspartate were inversely correlated with the R-1,R-H2O and positively correlated with the C-H2O of white matter. In addition, the Cramer-Rao lower bound was biased regarding the metabolite concentration, suggesting that should not be used as a quality assessment. ConclusionThe implemented method was fast, robust, and user-independent.

    Keywords
    1H-MRS, qMRI, LCModel, White matter, Thalamus, Age
    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-85921 (URN)10.1002/mrm.24554 (DOI)000325136300002 ()
    Available from: 2012-12-03 Created: 2012-12-03 Last updated: 2019-06-14
    2. Increased Concentrations of Glutamate and Glutamine in Normal Appearing White Matter of Patients with Multiple Sclerosis and Normal MR Imaging Brain Scans
    Open this publication in new window or tab >>Increased Concentrations of Glutamate and Glutamine in Normal Appearing White Matter of Patients with Multiple Sclerosis and Normal MR Imaging Brain Scans
    Show others...
    2013 (English)In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 8, no 4Article in journal (Refereed) Published
    Abstract [en]

    In Multiple Sclerosis (MS) the relationship between disease process in normal-appearing white matter (NAWM) and the development of white matter lesions is not well understood. In this study we used single voxel proton ‘Quantitative Magnetic Resonance Spectroscopy’ (qMRS) to characterize the NAWM and thalamus both in atypical ‘Clinically Definite MS’ (CDMS) patients, MRIneg (N = 15) with very few lesions (two or fewer lesions), and in typical CDMS patients, MRIpos (N = 20) with lesions, in comparison with healthy control subjects (N = 20). In addition, the metabolite concentrations were also correlated with extent of brain atrophy measured using Brain Parenchymal Fraction (BPF) and severity of the disease measured using ‘Multiple Sclerosis Severity Score’ (MSSS). Elevated concentrations of glutamate and glutamine (Glx) were observed in both MS groups (MRIneg 8.12 mM, p<0.001 and MRIpos 7.96 mM p<0.001) compared to controls, 6.76 mM. Linear regressions of Glx and total creatine (tCr) with MSSS were 0.16±0.06 mM/MSSS (p = 0.02) for Glx and 0.06±0.03 mM/MSSS (p = 0.04) for tCr, respectively. Moreover, linear regressions of tCr and myo-Inositol (mIns) with BPF were −6.22±1.63 mM/BPF (p<0.001) for tCr and −7.71±2.43 mM/BPF (p = 0.003) for mIns. Furthermore, the MRIpos patients had lower N-acetylaspartate and N-acetylaspartate-glutamate (tNA) and elevated mIns concentrations in NAWM compared to both controls (tNA: p = 0.04 mIns p<0.001) and MRIneg (tNA: p = 0.03 , mIns: p = 0.002). The results suggest that Glx may be an important marker for pathology in non-lesional white matter in MS. Moreover, Glx is related to the severity of MS independent of number of lesions in the patient. In contrast, increased glial density indicated by increased mIns and decreased neuronal density indicated by the decreased tNA, were only observed in NAWM of typical CDMS patients with white matter lesions.

    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-85924 (URN)10.1371/journal.pone.0061817 (DOI)000317907200090 ()23613944 (PubMedID)
    Available from: 2012-12-03 Created: 2012-12-03 Last updated: 2019-06-14Bibliographically approved
    3. Association between Change in Normal Appearing White Matter Metabolites and Intrathecal Inflammation in Natalizumab-Treated Multiple Sclerosis
    Open this publication in new window or tab >>Association between Change in Normal Appearing White Matter Metabolites and Intrathecal Inflammation in Natalizumab-Treated Multiple Sclerosis
    Show others...
    2012 (English)In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 7, no 9, p. e44739-Article in journal (Refereed) Published
    Abstract [en]

    Background: Multiple sclerosis (MS) is associated not only with focal inflammatory lesions but also diffuse pathology in the central nervous system (CNS). Since there is no firm association between the amount of focal inflammatory lesions and disease severity, diffuse pathology in normal appearing white matter (NAWM) may be crucial for disease progression. Immunomodulating treatments for MS reduce the number of focal lesions, but possible effects on diffuse white matter pathology are less studied. Furthermore, it is not known whether intrathecal levels of inflammatory or neurodegenerative markers are associated with development of pathology in NAWM.

    Methods: Quantitative proton magnetic resonance spectroscopy (1H-MRS) was used to investigate NAWM in 27 patients with relapsing MS before and after one year of treatment with natalizumab as well as NAWM in 20 healthy controls at baseline. Changes in 1H-MRS metabolite concentrations during treatment were also correlated with a panel of intrathecal markers of inflammation and neurodegeneration in 24 of these 27 patients.

    Results: The group levels of 1H-MRS metabolite concentrations were unchanged pre-to posttreatment, but a pattern of high magnitude correlation coefficients (r = 0.43–0.67, p<0.0005–0.03) were found between changes in individual metabolite concentrations (total creatine and total choline) and levels of pro-inflammatory markers (IL-1β and CXCL8).

    Conclusions: Despite a clinical improvement and a global decrease in levels of inflammatory markers in cerebrospinal fluid during treatment, high levels of pro-inflammatory CXCL8 and IL-1β were associated with an increase in 1H-MRS metabolites indicative of continued gliosis development and membrane turnover in NAWM.

    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-84270 (URN)10.1371/journal.pone.0044739 (DOI)000309742800016 ()
    Note

    funding agencies|Swedish Society of Neurologically Disabled||Swedish Society of Medicine||National Research Council (VR/NT)||University Hospital of Linkoping||County Council of Ostergotland||Teva||Biogen Idec||

    Available from: 2012-10-03 Created: 2012-10-03 Last updated: 2019-06-14
    4. Reduced thalamic N-acetylaspartate in idiopathic normal pressure hydrocephalus: a controlled (1)H-magnetic resonance spectroscopy study of frontal deep white matter and the thalamus using absolute quantification
    Open this publication in new window or tab >>Reduced thalamic N-acetylaspartate in idiopathic normal pressure hydrocephalus: a controlled (1)H-magnetic resonance spectroscopy study of frontal deep white matter and the thalamus using absolute quantification
    Show others...
    2011 (English)In: Journal of Neurology, Neurosurgery and Psychiatry, ISSN 0022-3050, E-ISSN 1468-330X, Vol. 82, no 7, p. 772-778Article in journal (Refereed) Published
    Abstract [en]

    Introduction Patients with idiopathic normal pressure hydrocephalus (INPH) frequently have a reduction in cerebral blood flow in the subcortical frontal lobe/basal ganglia/thalamic areas. With magnetic resonance spectroscopy, the metabolism in the brain can be examined. The aim of this study was to investigate if there was a compromised metabolism in the thalamus and in the subcortical frontal areas in INPH patients. This was done by measuring total creatine, myo-inositol, total choline, N-acetylaspartate (NAA), total N-acetylaspartate (tNA), glutamate and lactate levels. A comparison was made with healthy individuals (HI). Subjects and methods 16 patients (nine males, seven females, mean age 74 years, range 49-83) diagnosed as INPH and 15 HI (nine males, six females, mean age 74 years, range 62-89) were examined. 1 H magnetic resonance spectroscopy (1.5 T, point-resolved spectroscopy, echo time/relaxation time 30/3000 ms, volume of interest 2.5-3 ml) was performed in frontal deep white matter and in the thalamus. Absolute quantification with internal water as a reference was used. Results INPH patients had lower NAA (p = 0.02) and lower tNA (p = 0.05) concentrations in the thalamus compared with HI. NAA and tNA in the frontal deep white matter did not differ between patients and HI. The absolute metabolic concentrations of total creatine, myoinositol total choline, tNA, lactate and Cr ratios in frontal deep white matter and in the thalamus were similar in INPH patients and HI. Conclusion Reduced thalamic NAA and tNA in INPH patients suggest a compromised metabolic neuronal function in these regions. Thus, the thalamus might have an important role in the pathogenesis of INPH.

    Place, publisher, year, edition, pages
    BMJ Publishing Group, 2011
    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-69842 (URN)10.1136/jnnp.2010.223529 (DOI)000291429200016 ()
    Note

    Original Publication: Fredrik Lundin, Anders Tisell, Olof Dahlqvist Leinhard, M. Tullberg, C. Wikkelso, Peter Lundberg and Göran Leijon, Reduced thalamic N-acetylaspartate in idiopathic normal pressure hydrocephalus: a controlled (1)H-magnetic resonance spectroscopy study of frontal deep white matter and the thalamus using absolute quantification, 2011, Journal of Neurology, Neurosurgery and Psychiatry, (82), 7, 772-778. http://dx.doi.org/10.1136/jnnp.2010.223529 Copyright: BMJ Publishing Group http://group.bmj.com/

    Available from: 2011-08-10 Created: 2011-08-08 Last updated: 2019-06-14
    5. Low Thalamic NAA-Concentration Corresponds to Strong Neural Activation in Working Memory in Kleine-Levin Syndrome
    Open this publication in new window or tab >>Low Thalamic NAA-Concentration Corresponds to Strong Neural Activation in Working Memory in Kleine-Levin Syndrome
    Show others...
    2013 (English)In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 8, no 2Article in journal (Refereed) Published
    Abstract [en]

    Background

    Kleine Levin Syndrome (KLS) is a rare disorder of periodic hypersomnia and behavioural disturbances in young individuals. It has previously been shown to be associated with disturbances of working memory (WM), which, in turn, was associated with higher activation of the thalamus with increasing WM load, demonstrated with functional magnetic resonance imaging (fMRI). In this study we aimed to further elucidate how these findings are related to the metabolism of the thalamus.

    Methods

    fMRI and magnetic resonance spectroscopy were applied while performing a WM task. Standard metabolites were examined: n-acetylaspartate (NAA), myo-inositol, choline, creatine and glutamate-glutamine. Fourteen KLS-patients and 15 healthy controls participated in the study. The patients with active disease were examined in asymptomatic periods.

    Results

    There was a statistically significant negative correlation between thalamic fMRI-activation and thalamic NAA, i.e., high fMRI-activation corresponded to low NAA-levels. This correlation was not seen in healthy controls. Thalamic levels of NAA in patients and controls showed no significant differences between the groups. None of the other metabolites showed any co-variation with fMRI-activiation.

    Conclusion

    This study shows negative correlation between NAA-levels and fMRI-activity in the left thalamus of KLS-patients while performing a WM task. This correlation could not be found in healthy control subjects, primarily interpreted as an effect of increased effort in the patient group upon performing the task. It might indicate a disturbance in the neuronal networks responsible for WM in KLS patients, resulting in higher effort at lower WM load, compared with healthy subjects. The general relationship between NAA and BOLD-signal is also discussed in the article.

    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-85927 (URN)10.1371/journal.pone.0056279 (DOI)000316849500009 ()
    Available from: 2012-12-03 Created: 2012-12-03 Last updated: 2019-06-14Bibliographically approved
  • 277.
    Tisell, Anders
    et al.
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics.
    Dahlqvist Leinhard, Olof
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics.
    Warntjes, Jan Bertus Marcel
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Clinical Physiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Clinical Physiology in Linköping.
    Aalto, Arne
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences.
    Smedby, Örjan
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Landtblom, Anne-Marie
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Clinical and Experimental Medicine, Neurology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Local Health Care Services in Central Östergötland, Department of Neurology. Östergötlands Läns Landsting, Local Health Care Services in West Östergötland, Department of Medical Specialist in Motala.
    Lundberg, Peter
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Increased Concentrations of Glutamate and Glutamine in Normal Appearing White Matter of Patients with Multiple Sclerosis and Normal MR Imaging Brain Scans2013In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 8, no 4Article in journal (Refereed)
    Abstract [en]

    In Multiple Sclerosis (MS) the relationship between disease process in normal-appearing white matter (NAWM) and the development of white matter lesions is not well understood. In this study we used single voxel proton ‘Quantitative Magnetic Resonance Spectroscopy’ (qMRS) to characterize the NAWM and thalamus both in atypical ‘Clinically Definite MS’ (CDMS) patients, MRIneg (N = 15) with very few lesions (two or fewer lesions), and in typical CDMS patients, MRIpos (N = 20) with lesions, in comparison with healthy control subjects (N = 20). In addition, the metabolite concentrations were also correlated with extent of brain atrophy measured using Brain Parenchymal Fraction (BPF) and severity of the disease measured using ‘Multiple Sclerosis Severity Score’ (MSSS). Elevated concentrations of glutamate and glutamine (Glx) were observed in both MS groups (MRIneg 8.12 mM, p<0.001 and MRIpos 7.96 mM p<0.001) compared to controls, 6.76 mM. Linear regressions of Glx and total creatine (tCr) with MSSS were 0.16±0.06 mM/MSSS (p = 0.02) for Glx and 0.06±0.03 mM/MSSS (p = 0.04) for tCr, respectively. Moreover, linear regressions of tCr and myo-Inositol (mIns) with BPF were −6.22±1.63 mM/BPF (p<0.001) for tCr and −7.71±2.43 mM/BPF (p = 0.003) for mIns. Furthermore, the MRIpos patients had lower N-acetylaspartate and N-acetylaspartate-glutamate (tNA) and elevated mIns concentrations in NAWM compared to both controls (tNA: p = 0.04 mIns p<0.001) and MRIneg (tNA: p = 0.03 , mIns: p = 0.002). The results suggest that Glx may be an important marker for pathology in non-lesional white matter in MS. Moreover, Glx is related to the severity of MS independent of number of lesions in the patient. In contrast, increased glial density indicated by increased mIns and decreased neuronal density indicated by the decreased tNA, were only observed in NAWM of typical CDMS patients with white matter lesions.

  • 278.
    Tisell, Anders
    et al.
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics.
    Dahlqvist Leinhard, Olof
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics.
    Warntjes, Jan Bertus Marcel
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Clinical Physiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Clinical Physiology in Linköping.
    Lundberg, Peter
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Procedure for Quantitative 1H Magnetic Resonance Spectroscopy and Tissue Characterization of Human Brain Tissue Based on the Use of Quantitative Magnetic Resonance Imaging2013In: Magnetic Resonance in Medicine, ISSN 0740-3194, E-ISSN 1522-2594, Vol. 70, no 4, p. 905-915Article in journal (Refereed)
    Abstract [en]

    PurposeExisting methods for quantitative magnetic resonance spectroscopy are not widely used for magnetic resonance spectroscopy examinations in clinical practice due to the lengthy and difficult workflow. In this report, we aimed to investigate whether metabolite concentrations show co-variation with relaxation parameters (R-1,R-H2O,R-2,R-H2O), water concentration (C-H2O), and age, using a quantitative magnetic resonance spectroscopy method, which is suitable for a clinical setting. MethodsWe performed 166 single voxel magnetic resonance spectroscopy measurements in the white matter and thalamus in 47 healthy subjects, aged 18-72 years. Whole brain R-1,R-H2O, R-2,R-H2O, and C-H2O maps were determined for each subject using quantitative magnetic resonance imaging. Absolute metabolite concentrations were calculated by calibrating the water-scaled magnetic resonance spectroscopy, using the quantitative magnetic resonance imaging maps of R-1,R-H2O, R-2,R-H2O, and C-H2O. ResultsAbsolute concentrations in white matter of total Creatine and myo-Inositol were correlated with age (total Creatine: 12 4 M/year, P < 0.01; myo-Inositol: 23 +/- 9 M/year, P < 0.05), suggesting a process of increased glia density in aging white matter. Moreover, total Creatine and total N-acetylaspartate were inversely correlated with the R-1,R-H2O and positively correlated with the C-H2O of white matter. In addition, the Cramer-Rao lower bound was biased regarding the metabolite concentration, suggesting that should not be used as a quality assessment. ConclusionThe implemented method was fast, robust, and user-independent.

  • 279.
    Tisell, Anders
    et al.
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medical and Health Sciences, Radiation Physics. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Dahlqvist Leinhard, Olof
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Warntjes, Marcel, Jan Bertus
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medical and Health Sciences, Clinical Physiology. Östergötlands Läns Landsting, Heart Centre, Department of Clinical Physiology. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Engström, Maria
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Landtblom, Anne-Marie
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Clinical and Experimental Medicine. Östergötlands Läns Landsting, Local Health Care Services in Central Östergötland, Department of Neurology. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Lundberg, Peter
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics. Östergötlands Läns Landsting, Centre for Medical Imaging, Department of Radiology in Linköping.
    Absolute quantification of LCModel water scaled metabolite concentration of 1H magnetic resonance spectroscopy (MRS) using quantitative magnetic resoonance imaging (qMRI)2008In: ESMRMB,2008, 2008Conference paper (Other academic)
    Abstract [en]

      

  • 280.
    Tisell, Anders
    et al.
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medicine and Health Sciences, Radiation Physics. Östergötlands Läns Landsting, Centre for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics UHL. Linköping University, Faculty of Health Sciences.
    Dahlqvist Leinhard, Olof
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medicine and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Warntjes, Marcel
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medicine and Health Sciences. Linköping University, Faculty of Health Sciences.
    West, Janne
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medicine and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Lundberg, Peter
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medicine and Health Sciences, Radiation Physics. Linköping University, Department of Medicine and Health Sciences, Radiology. Östergötlands Läns Landsting, Centre for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics UHL. Östergötlands Läns Landsting, Centre for Diagnostics, Department of Radiology in Linköping. Linköping University, Faculty of Health Sciences.
    Absolute quantification of 1H Magnetic Resonance Spectroscopy of human brain using qMRI2009Conference paper (Other academic)
  • 281.
    Tisell, Anders
    et al.
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medicine and Health Sciences, Radiation Physics. Östergötlands Läns Landsting, Centre for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics UHL. Linköping University, Faculty of Health Sciences.
    Engström, Maria
    Linköping University, Department of Medicine and Health Sciences, Radiology. Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Faculty of Health Sciences.
    Dahlqvist Leinhard, Olof
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medicine and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Karlsson, T
    Vigren, P
    Landtblom, Anne-Marie
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Clinical and Experimental Medicine, Psychiatry. Östergötlands Läns Landsting, Sinnescentrum, Department of Neurosurgery UHL. Linköping University, Faculty of Health Sciences.
    Lundberg, Peter
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medicine and Health Sciences, Radiation Physics. Linköping University, Department of Medicine and Health Sciences, Radiology. Östergötlands Läns Landsting, Centre for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics UHL. Östergötlands Läns Landsting, Centre for Diagnostics, Department of Radiology in Linköping. Linköping University, Faculty of Health Sciences.
    Combining fMRI with qMRS for understanding the etiology of periodic hypersomnia2009Conference paper (Other academic)
  • 282.
    Tisell, Anders
    et al.
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medical and Health Sciences, Radiation Physics. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Engström, Maria
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Karlsson, Thomas
    Linköping University, Faculty of Arts and Sciences. Linköping University, Department of Behavioural Sciences and Learning. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Vigren, Patrik
    NSC.
    Dahlqvist Leinhard, Olof
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Lundberg, Peter
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics. Östergötlands Läns Landsting, Centre for Medical Imaging, Department of Radiology in Linköping.
    Etiology of periodic hypersomnia explored by combined functional and molecular neuroimaging methods2008In: World Molecular Imaging Conference,,2008, 2008Conference paper (Other academic)
    Abstract [en]

      

  • 283.
    Tisell, Anders
    et al.
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics UHL.
    Mellergård, Johan
    Linköping University, Department of Clinical and Experimental Medicine, Neurology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Local Health Care Services in Central Östergötland, Department of Neurology.
    Dahlqvist Leinhard, Olof
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Dahle, Charlotte
    Linköping University, Department of Clinical and Experimental Medicine, Clinical Immunology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Diagnostics, Department of Clinical Immunology and Transfusion Medicine.
    Ernerudh, Jan
    Linköping University, Department of Clinical and Experimental Medicine, Clinical Immunology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Diagnostics, Department of Clinical Immunology and Transfusion Medicine.
    Vrethem, Magnus
    Linköping University, Department of Clinical and Experimental Medicine, Neurology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Local Health Care Services in Central Östergötland, Department of Neurology.
    Landtblom, Anne-Marie
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Clinical and Experimental Medicine, Neurology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Local Health Care Services in Central Östergötland, Department of Neurology.
    Lundberg, Peter
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics UHL.
    Brain Atrophy in MS Patients Correlates with Creatine Concentrations2012Conference paper (Other academic)
  • 284.
    Tisell, Anders
    et al.
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics UHL.
    Mellergård, Johan
    Linköping University, Department of Clinical and Experimental Medicine, Neurology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Local Health Care Services in Central Östergötland, Department of Neurology.
    Dahlqvist Leinhard, Olof
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Dahle, Charlotte
    Linköping University, Department of Clinical and Experimental Medicine, Clinical Immunology. Linköping University, Faculty of Health Sciences.
    Ernerudh, Jan
    Linköping University, Department of Clinical and Experimental Medicine, Clinical Immunology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Diagnostics, Department of Clinical Immunology and Transfusion Medicine.
    Vrethem, Magnus
    Linköping University, Department of Clinical and Experimental Medicine, Neurology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Local Health Care Services in Central Östergötland, Department of Neurology.
    Landtblom, Anne-Marie
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Clinical and Experimental Medicine, Neurology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Local Health Care Services in Central Östergötland, Department of Neurology. Östergötlands Läns Landsting, Local Health Care Services in the West of Östergötland, Department of Medical Specialist.
    Lundberg, Peter
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics UHL. Östergötlands Läns Landsting, Centre for Diagnostics, Department of Radiology in Linköping.
    Increased Glia in Multiple Sclerosis Patients Correlates with Intrathecal Inflammation2011Conference paper (Refereed)
  • 285.
    Tisell, Anders
    et al.
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medical and Health Sciences, Radiation Physics. Östergötlands Läns Landsting, Centre for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics UHL. Linköping University, Faculty of Health Sciences.
    Mellergård, Johan
    Linköping University, Department of Clinical and Experimental Medicine, Neurology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Local Health Care Services in Central Östergötland, Department of Neurology.
    Dahlqvist Leinhard, Olof
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Dahle, Charlotte
    Linköping University, Department of Clinical and Experimental Medicine, Clinical Immunology. Linköping University, Faculty of Health Sciences.
    Ernerudh, Jan
    Linköping University, Department of Clinical and Experimental Medicine, Clinical Immunology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Diagnostics, Department of Clinical Immunology and Transfusion Medicine.
    Vrethem, Magnus
    Linköping University, Department of Clinical and Experimental Medicine, Neurology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Local Health Care Services in Central Östergötland, Department of Neurology.
    Landtblom, Anne-Marie
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Clinical and Experimental Medicine, Neurology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Local Health Care Services in Central Östergötland, Department of Neurology. Östergötlands Läns Landsting, Local Health Care Services in the West of Östergötland, Department of Medical Specialist.
    Lundberg, Peter
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics UHL. Östergötlands Läns Landsting, Centre for Diagnostics, Department of Radiology in Linköping.
    Multiple Sclerosis Severity Score (MSSS) Correlates With Changes in NAWM Metabolism During Treatment2011Conference paper (Refereed)
  • 286.
    Toll, Pia
    et al.
    Östergötlands Läns Landsting, Heart and Medicine Centre, Department of Clinical Physiology UHL.
    Olsson, Eva
    Östergötlands Läns Landsting, Heart and Medicine Centre, Department of Clinical Physiology UHL.
    Gustafsson, Agnetha
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics UHL.
    Erfarenheter från avvikelsehantering i Linköping2010Conference paper (Other academic)
  • 287.
    Ullman, Gustaf
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Quantifying image quality in diagnostic radiology using simulation of the imaging system and model observers2008Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Accurate measures of both clinical image quality and patient radiation risk are needed for successful optimisation of medical imaging with ionising radiation. Optimisation in diagnostic radiology means finding the image acquisition technique that maximises the perceived information content and minimises the radiation risk or keeps it at a reasonably low level. The assessment of image quality depends on the diagnostic task and may in addition to system and quantum noise also be hampered by overlying projected anatomy.

    The main objective of this thesis is to develop methods for assessment of image quality in simulations of projection radiography. In this thesis, image quality is quantified by modelling the whole x‐ray imaging system including the x‐ray tube, patient, anti‐scatter device, image detector and the observer. This is accomplished by using Monte Carlo (MC) simulation methods that allow simultaneous estimates of measures of image quality and patient dose. Measures of image quality include the signal‐to‐noise‐ratio, SNR, of pathologic lesions and radiation risk is estimated by using organ doses to calculate the effective dose. Based on high‐resolution anthropomorphic phantoms, synthetic radiographs were calculated and used for assessing image quality with model‐observers (Laguerre‐Gauss (LG) Hotelling observer) that mimic real, human observers. Breast and particularly chest imaging were selected as study cases as these are particularly challenging for the radiologists.

    In chest imaging the optimal tube voltage in detecting lung lesions was investigated in terms of their SNR and the contrast of the lesions relative to the ribs. It was found that the choice of tube voltage depends on whether SNR of the lesion or the interfering projected anatomy (i.e. the ribs) is most important for detection. The Laguerre‐Gauss (LG) Hotelling observer is influenced by the projected anatomical background and includes this into its figure‐of‐merit, SNRhot,LG. The LG‐observer was found to be a better model of the radiologist than the ideal observer that only includes the quantum noise in its analysis. The measures of image quality derived from our model are found to correlate relatively well with the radiologist’s assessment of image quality. Therefore MC simulations can be a valuable and an efficient tool in the search for dose‐efficient imaging systems and image acquisition schemes.

    List of papers
    1. A search for optimal x‐ray spectra in iodine contrast media mammography
    Open this publication in new window or tab >>A search for optimal x‐ray spectra in iodine contrast media mammography
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    2005 (English)In: Physics in medicine and biology, ISSN 0031-9155, Vol. 50, no 13, p. 3143-3152Article in journal (Refereed) Published
    Abstract [en]

    The aim of this work was to search for the optimal x-ray tube voltage and anode–filter combination in digital iodine contrast media mammography. In the optimization, two entities were of interest: the average glandular dose, AGD, and the signal-to-noise ratio, SNR, for detection of diluted iodine contrast medium. The optimum is defined as the technique maximizing the figure of merit, SNR2/AGD. A Monte Carlo computer program was used which simulates the transport of photons from the x-ray tube through the compression plate, breast, breast support plate, anti-scatter grid and image detector. It computes the AGD and the SNR of an iodine detail inside the compressed breast. The breast thickness was varied between 2 and 8 cm with 10–90% glandularity. The tube voltage was varied between 20 and 55 kV for each anode material (Rh, Mo and W) in combination with either 25 µm Rh or 0.05–0.5 mm Cu added filtration. The x-ray spectra were calculated with MCNP4C (Monte Carlo N-Particle Transport Code System, version 4C). A CsI scintillator was used as the image detector. The results for Rh/0.3mmCu, Mo/0.3mmCu and W/0.3mmCu were similar. For all breast thicknesses, a maximum in the figure of merit was found at approximately 45 kV for the Rh/Cu, Mo/Cu and W/Cu combinations. The corresponding results for the Rh/Rh combination gave a figure of merit that was typically lower and more slowly varying with tube voltage. For a 4 cm breast at 45 kV, the SNR2/AGD was 3.5 times higher for the Rh/0.3mmCu combination compared with the Rh/Rh combination. The difference is even larger for thicker breasts. The SNR2/AGD increases slowly with increasing Cu-filter thickness. We conclude that tube voltages between 41 and 55 kV and added Cu-filtration will result in significant dose advantage in digital iodine contrast media mammography compared to using the Rh/Rh anode/filter combination at 25–32 kV.

    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-13217 (URN)10.1088/0031-9155/50/13/012 (DOI)
    Available from: 2008-04-28 Created: 2008-04-28 Last updated: 2015-03-20
    2. Distributions of scatter to primary ratios and signal to noise ratios per pixel in digital chest imaging
    Open this publication in new window or tab >>Distributions of scatter to primary ratios and signal to noise ratios per pixel in digital chest imaging
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    2005 (English)In: Radiation protection dosimetry, ISSN 0144-8420, Vol. 114, no 1-3, p. 355-358Article in journal (Refereed) Published
    Abstract [en]

    The aim of this work was to calculate distributions of scatter-to-primary ratios (s/p) and signal-to-noise ratios per pixel (SNRp) in chest images. Such distributions may provide useful information on how physical image quality (contrast, SNR) is distributed over the posterior/anterior (PA) chest image. A Monte Carlo computer program was used for the calculations, including a model of both the patient (voxel phantom) and the imaging system (X-ray tube, anti-scatter grid and image detector). The calculations were performed for three PA thicknesses 20, 24 and 28 cm. For a 24 cm patient, the s/p varies between 0.5 in the lung to 2.5 behind the spine and heart. The corresponding variation of the SNRp is a factor of 3, with the highest values in the lung. Increasing the patient thickness from 20 to 28 cm increases the s/p by a factor of 2.2 behind the spine and heart.

    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-13218 (URN)10.1093/rpd/nch530 (DOI)
    Available from: 2008-04-28 Created: 2008-04-28 Last updated: 2015-03-20
    3. Towards optimization in digital chest radiography using Monte Carlo modelling
    Open this publication in new window or tab >>Towards optimization in digital chest radiography using Monte Carlo modelling
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    2006 (English)In: Physics in medicine and biology, ISSN 0031-9155, Vol. 51, no 11, p. 2729-2743Article in journal (Refereed) Published
    Abstract [en]

    A Monte Carlo based computer model of the x-ray imaging system was used to investigate how various image quality parameters of interest in chest PA radiography and the effective dose E vary with tube voltage (90–150 kV), additional copper filtration (0–0.5 mm), anti-scatter method (grid ratios 8–16 and air gap lengths 20–40 cm) and patient thickness (20–28 cm) in a computed radiography (CR) system. Calculated quantities were normalized to a fixed value of air kerma (5.0 µGy) at the automatic exposure control chambers. Soft-tissue nodules were positioned at different locations in the anatomy and calcifications in the apical region. The signal-to-noise ratio, SNR, of the nodules and the nodule contrast relative to the contrast of bone (C/CB) as well as relative to the dynamic range in the image (Crel) were used as image quality measures. In all anatomical regions, except in the densest regions in the thickest patients, the air gap technique provides higher SNR and contrast ratios than the grid technique and at a lower effective dose E. Choice of tube voltage depends on whether quantum noise (SNR) or the contrast ratios are most relevant for the diagnostic task. SNR increases with decreasing tube voltage while C/CB increases with increasing tube voltage.

    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-13219 (URN)10.1088/0031-9155/51/11/003 (DOI)
    Available from: 2008-04-28 Created: 2008-04-28 Last updated: 2015-03-20
    4. Comparison of clinical and physical measures of image quality in chest and pelvis computed radiography at different tube voltages
    Open this publication in new window or tab >>Comparison of clinical and physical measures of image quality in chest and pelvis computed radiography at different tube voltages
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    2006 (English)In: Medical physics (Lancaster), ISSN 0094-2405, Vol. 33, no 11, p. 4169-4175Article in journal (Refereed) Published
    Abstract [en]

    The aim of this work was to study the dependence of image quality in digital chest and pelvis radiography on tube voltage, and to explore correlations between clinical and physical measures of image quality. The effect on image quality of tube voltage in these two examinations was assessed using two methods. The first method relies on radiologists' observations of images of an anthropomorphic phantom, and the second method was based on computer modeling of the imaging system using an anthropomorphic voxel phantom. The tube voltage was varied within a broad range (50–150  kV), including those values typically used with screen-film radiography. The tube charge was altered so that the same effective dose was achieved for each projection. Two x-ray units were employed using a computed radiography (CR) image detector with standard tube filtration and antiscatter device. Clinical image quality was assessed by a group of radiologists using a visual grading analysis (VGA) technique based on the revised CEC image criteria. Physical image quality was derived from a Monte Carlo computer model in terms of the signal-to-noise ratio, SNR, of anatomical structures corresponding to the image criteria. Both the VGAS (visual grading analysis score) and SNR decrease with increasing tube voltage in both chest PA and pelvis AP examinations, indicating superior performance if lower tube voltages are employed. Hence, a positive correlation between clinical and physical measures of image quality was found. The pros and cons of using lower tube voltages with CR digital radiography than typically used in analog screen-film radiography are discussed, as well as the relevance of using VGAS and quantum-noise SNR as measures of image quality in pelvis and chest radiography.

    Keywords
    diagnostic radiography, Monte Carlo methods, image denoising, dosimetry, phantoms, biomedical equipment
    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-13220 (URN)10.1118/1.2362871 (DOI)
    Available from: 2008-04-28 Created: 2008-04-28 Last updated: 2017-12-13
    5. Calculation of images from an anthropomorphic chest phantom using Monte Carlo methods
    Open this publication in new window or tab >>Calculation of images from an anthropomorphic chest phantom using Monte Carlo methods
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    2006 (English)In: Proceedings of SPIE, 2006, Vol. 6142Conference paper, Published paper (Refereed)
    Abstract [en]

    Monte Carlo (MC) computer simulation of chest x-ray imaging systems has hitherto been performed using anthropomorphic phantoms with too large (3 mm) voxel sizes. The aim for this work was to develop and use a Monte Carlo computer program to compute projection x-ray images of a high-resolution anthropomorphic voxel phantom for visual clinical image quality evaluation and dose-optimization. An Alderson anthropomorphic chest phantom was imaged in a CT-scanner and reconstructed with isotropic voxels of 0.7 mm. The phantom was segmented and included in a Monte Carlo computer program using the collision density estimator to derive the energies imparted to the detector per unit area of each pixel by scattered photons. The image due to primary photons was calculated analytically including a pre-calculated detector response function. Attenuation and scatter of x-rays in the phantom, grid and image detector was considered. Imaging conditions (tube voltage, anti-scatter device) were varied and the images compared to a real computed radiography (Fuji FCR 9501) image. Four imaging systems were simulated (two tube voltages 81 kV and 141 kV using either a grid with ratio 10 or a 30 cm air gap). The effect of scattered radiation on the visibility of thoracic vertebrae against the heart and lungs is demonstrated. The simplicity in changing the imaging conditions will allow us not only to produce images of existing imaging systems, but also of hypothetical, future imaging systems. We conclude that the calculated images of the high-resolution voxel phantom are suitable for human detection experiments of low-contrast lesions.

    Series
    ; 6142
    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-13221 (URN)10.1117/12.644119 (DOI)
    Available from: 2008-04-28 Created: 2008-04-28 Last updated: 2015-03-20
    6. Development of a Monte Carlo based model for optimization using the Laguerre‐Gauss Hotelling observer
    Open this publication in new window or tab >>Development of a Monte Carlo based model for optimization using the Laguerre‐Gauss Hotelling observer
    Show others...
    2008 (English)In: Medical physics, ISSN 0094-2405Article in journal (Refereed) Submitted
    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-13222 (URN)
    Available from: 2008-04-28 Created: 2008-04-28 Last updated: 2017-01-11
  • 288.
    Ullman, Gustaf
    et al.
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Båth, Magnus
    Alm Carlsson, Gudrun
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Dance, David R.
    Tapiovaara, Markku
    Sandborg, Michael
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Development of a Monte Carlo based model for optimization using the Laguerre‐Gauss Hotelling observer2008In: Medical physics, ISSN 0094-2405Article in journal (Refereed)
  • 289.
    Ullman, Gustaf
    et al.
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medicine and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Dance, David R.
    Royal Surrey County Hospital, Guildford.
    Sandborg, Michael
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medicine and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics.
    Alm Carlsson, Gudrun
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medicine and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics.
    Svalkvist, Angelica
    University of Gothenburg.
    Båth, Magnus
    University of Gothenburg.
    A Monte Carlo-based model for simulation of digital chest tomosynthesis2010In: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 139, no 1-3, p. 159-163Article in journal (Refereed)
    Abstract [en]

    The aim of this work was to calculate synthetic digital chest tomosynthesis projections using a computer simulation model based on the Monte Carlo method. An anthropomorphic chest phantom was scanned in a computed tomography scanner, segmented and included in the computer model to allow for simulation of realistic high-resolution X-ray images. The input parameters to the model were adapted to correspond to the VolumeRAD chest tomosynthesis system from GE Healthcare. Sixty tomosynthesis projections were calculated with projection angles ranging from +15 to −15°. The images from primary photons were calculated using an analytical model of the anti-scatter grid and a pre-calculated detector response function. The contributions from scattered photons were calculated using an in-house Monte Carlo-based model employing a number of variance reduction techniques such as the collision density estimator. Tomographic section images were reconstructed by transferring the simulated projections into the VolumeRAD system. The reconstruction was performed for three types of images using: (i) noise-free primary projections, (ii) primary projections including contributions from scattered photons and (iii) projections as in (ii) with added correlated noise. The simulated section images were compared with corresponding section images from projections taken with the real, anthropomorphic phantom from which the digital voxel phantom was originally created. The present article describes a work in progress aiming towards developing a model intended for optimisation of chest tomosynthesis, allowing for simulation of both existing and future chest tomosynthesis systems.

  • 290.
    Ullman, Gustaf
    et al.
    Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Linköping University, Faculty of Health Sciences.
    Malusek, Alexandr
    Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Linköping University, Faculty of Health Sciences.
    Sandborg, Michael
    Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Linköping University, Faculty of Health Sciences.
    Dance, David R.
    The Royal Marsden NHS Trust, United Kingdom.
    Alm Carlsson, Gudrun
    Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Linköping University, Faculty of Health Sciences.
    Calculation of images from an anthropomorphic chest phantom using Monte Carlo methods2006In: Proceedings of SPIE, 2006, Vol. 6142Conference paper (Refereed)
    Abstract [en]

    Monte Carlo (MC) computer simulation of chest x-ray imaging systems has hitherto been performed using anthropomorphic phantoms with too large (3 mm) voxel sizes. The aim for this work was to develop and use a Monte Carlo computer program to compute projection x-ray images of a high-resolution anthropomorphic voxel phantom for visual clinical image quality evaluation and dose-optimization. An Alderson anthropomorphic chest phantom was imaged in a CT-scanner and reconstructed with isotropic voxels of 0.7 mm. The phantom was segmented and included in a Monte Carlo computer program using the collision density estimator to derive the energies imparted to the detector per unit area of each pixel by scattered photons. The image due to primary photons was calculated analytically including a pre-calculated detector response function. Attenuation and scatter of x-rays in the phantom, grid and image detector was considered. Imaging conditions (tube voltage, anti-scatter device) were varied and the images compared to a real computed radiography (Fuji FCR 9501) image. Four imaging systems were simulated (two tube voltages 81 kV and 141 kV using either a grid with ratio 10 or a 30 cm air gap). The effect of scattered radiation on the visibility of thoracic vertebrae against the heart and lungs is demonstrated. The simplicity in changing the imaging conditions will allow us not only to produce images of existing imaging systems, but also of hypothetical, future imaging systems. We conclude that the calculated images of the high-resolution voxel phantom are suitable for human detection experiments of low-contrast lesions.

  • 291.
    Ullman, Gustaf
    et al.
    Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Linköping University, Faculty of Health Sciences.
    Sandborg, Michael
    Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Linköping University, Faculty of Health Sciences.
    Dance, David R.
    Joint Department of Physics, The Royal Marsden NHS Foundation Trust and Institute of Cancer Research, London, UK.
    Hunt, Roger A.
    Joint Department of Physics, The Royal Marsden NHS Foundation Trust and Institute of Cancer Research, London, UK.
    Alm Carlsson, Gudrun
    Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Linköping University, Faculty of Health Sciences.
    Towards optimization in digital chest radiography using Monte Carlo modelling2006In: Physics in medicine and biology, ISSN 0031-9155, Vol. 51, no 11, p. 2729-2743Article in journal (Refereed)
    Abstract [en]

    A Monte Carlo based computer model of the x-ray imaging system was used to investigate how various image quality parameters of interest in chest PA radiography and the effective dose E vary with tube voltage (90–150 kV), additional copper filtration (0–0.5 mm), anti-scatter method (grid ratios 8–16 and air gap lengths 20–40 cm) and patient thickness (20–28 cm) in a computed radiography (CR) system. Calculated quantities were normalized to a fixed value of air kerma (5.0 µGy) at the automatic exposure control chambers. Soft-tissue nodules were positioned at different locations in the anatomy and calcifications in the apical region. The signal-to-noise ratio, SNR, of the nodules and the nodule contrast relative to the contrast of bone (C/CB) as well as relative to the dynamic range in the image (Crel) were used as image quality measures. In all anatomical regions, except in the densest regions in the thickest patients, the air gap technique provides higher SNR and contrast ratios than the grid technique and at a lower effective dose E. Choice of tube voltage depends on whether quantum noise (SNR) or the contrast ratios are most relevant for the diagnostic task. SNR increases with decreasing tube voltage while C/CB increases with increasing tube voltage.

  • 292.
    Ullman, Gustaf
    et al.
    Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Linköping University, Faculty of Health Sciences.
    Sandborg, Michael
    Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Linköping University, Faculty of Health Sciences.
    Dance, David R.
    Joint Department of Physics, The Royal Marsden NHS Trust, London, UK .
    Hunt, Roger
    Joint Department of Physics, The Royal Marsden NHS Trust, London, UK .
    Alm Carlsson, Gudrun
    Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Linköping University, Faculty of Health Sciences.
    Distributions of scatter to primary ratios and signal to noise ratios per pixel in digital chest imaging2005In: Radiation protection dosimetry, ISSN 0144-8420, Vol. 114, no 1-3, p. 355-358Article in journal (Refereed)
    Abstract [en]

    The aim of this work was to calculate distributions of scatter-to-primary ratios (s/p) and signal-to-noise ratios per pixel (SNRp) in chest images. Such distributions may provide useful information on how physical image quality (contrast, SNR) is distributed over the posterior/anterior (PA) chest image. A Monte Carlo computer program was used for the calculations, including a model of both the patient (voxel phantom) and the imaging system (X-ray tube, anti-scatter grid and image detector). The calculations were performed for three PA thicknesses 20, 24 and 28 cm. For a 24 cm patient, the s/p varies between 0.5 in the lung to 2.5 behind the spine and heart. The corresponding variation of the SNRp is a factor of 3, with the highest values in the lung. Increasing the patient thickness from 20 to 28 cm increases the s/p by a factor of 2.2 behind the spine and heart.

  • 293.
    Ullman, Gustaf
    et al.
    Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Linköping University, Faculty of Health Sciences.
    Sandborg, Michael
    Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Linköping University, Faculty of Health Sciences.
    Dance, David R.
    Joint Department of Physics, The Royal Marsden NHS Trust, London, UK.
    Yaffe, Martin
    Department of Medical Biophysics, University of Toronto, Sunnybrook and Women's College Health Sciences Centre, Ontario, Canada.
    Alm Carlsson, Gudrun
    Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Linköping University, Faculty of Health Sciences.
    A search for optimal x‐ray spectra in iodine contrast media mammography2005In: Physics in medicine and biology, ISSN 0031-9155, Vol. 50, no 13, p. 3143-3152Article in journal (Refereed)
    Abstract [en]

    The aim of this work was to search for the optimal x-ray tube voltage and anode–filter combination in digital iodine contrast media mammography. In the optimization, two entities were of interest: the average glandular dose, AGD, and the signal-to-noise ratio, SNR, for detection of diluted iodine contrast medium. The optimum is defined as the technique maximizing the figure of merit, SNR2/AGD. A Monte Carlo computer program was used which simulates the transport of photons from the x-ray tube through the compression plate, breast, breast support plate, anti-scatter grid and image detector. It computes the AGD and the SNR of an iodine detail inside the compressed breast. The breast thickness was varied between 2 and 8 cm with 10–90% glandularity. The tube voltage was varied between 20 and 55 kV for each anode material (Rh, Mo and W) in combination with either 25 µm Rh or 0.05–0.5 mm Cu added filtration. The x-ray spectra were calculated with MCNP4C (Monte Carlo N-Particle Transport Code System, version 4C). A CsI scintillator was used as the image detector. The results for Rh/0.3mmCu, Mo/0.3mmCu and W/0.3mmCu were similar. For all breast thicknesses, a maximum in the figure of merit was found at approximately 45 kV for the Rh/Cu, Mo/Cu and W/Cu combinations. The corresponding results for the Rh/Rh combination gave a figure of merit that was typically lower and more slowly varying with tube voltage. For a 4 cm breast at 45 kV, the SNR2/AGD was 3.5 times higher for the Rh/0.3mmCu combination compared with the Rh/Rh combination. The difference is even larger for thicker breasts. The SNR2/AGD increases slowly with increasing Cu-filter thickness. We conclude that tube voltages between 41 and 55 kV and added Cu-filtration will result in significant dose advantage in digital iodine contrast media mammography compared to using the Rh/Rh anode/filter combination at 25–32 kV.

  • 294.
    van Ettinger-Veenstra, Helene
    et al.
    Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Linköping University, Center for Medical Image Science and Visualization, CMIV.
    Gauffin, Helena
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Clinical and Experimental Medicine. Linköping University, Faculty of Health Sciences.
    McAllister, Anita
    Linköping University, Department of Clinical and Experimental Medicine, Speech and Language Pathology. Linköping University, Faculty of Health Sciences.
    Lundberg, Peter
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Linköping University, Center for Medical Image Science and Visualization, CMIV. Östergötlands Läns Landsting, Centre for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics UHL.
    Karlsson, Thomas
    Linköping University, Department of Behavioural Sciences and Learning.
    Engström, Maria
    Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Linköping University, Center for Medical Image Science and Visualization, CMIV.
    Language deficits in Epilepsy, an fMRI study2012In:  , 2012Conference paper (Refereed)
  • 295.
    van Ettinger-Veenstra, Helene
    et al.
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences.
    Gauffin, Helena
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Clinical and Experimental Medicine, Neurology. Linköping University, Faculty of Health Sciences.
    McAllister, Anita
    Linköping University, Department of Clinical and Experimental Medicine, Speech and Language Pathology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Sinnescentrum, Department of ENT - Head and Neck Surgery UHL.
    Lundberg, Peter
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics UHL.
    Ulrici, Daniel
    Östergötlands Läns Landsting, Local Health Care Services in Central Östergötland, Department of Neurology.
    Landtblom, Anne-Marie
    Östergötlands Läns Landsting, Local Health Care Services in Central Östergötland, Department of Neurology. Linköping University, Department of Clinical and Experimental Medicine, Neurology. Linköping University, Faculty of Health Sciences.
    Karlsson, Thomas
    Linköping University, Department of Behavioural Sciences and Learning. Linköping University, Faculty of Arts and Sciences.
    Engström, Maria
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences.
    Language deficits in Epilepsy, an fMRI study2012Conference paper (Other academic)
    Abstract [en]

    Cognitive functions in people with epilepsy are affected by focality, number of generalized seizures, side effects of antiepileptic drugs (AEDs) or the underlying disease (Kwan, 2001). Newly diagnosed patients have cognitive deficits even before starting on AEDs. Performance declines already in the first year after diagnosis and the impairment continues in the following years (Taylor, 2010; Baker, 2011). In mesial temporal lobe epilepsy (TLE) the hippocampal damage seems to be progressive and accompanied by thinning of neocortex (Briellmann, 2002; Bernhardt, 2009). Widespread structural and functional abnormalities in left TLE can affect more distant networks (Bonilha, 2009); a damage pattern also seen in right TLE (Karunanayaka, 2011).

  • 296.
    van Ettinger-Veenstra, Helene M
    et al.
    Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Linköping University, Center for Medical Image Science and Visualization, CMIV.
    Ragnehed, Mattias
    Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Linköping University, Center for Medical Image Science and Visualization, CMIV.
    Hällgren, Mathias
    Linköping University, Department of Clinical and Experimental Medicine, Technical Audiology. Linköping University, Faculty of Health Sciences.
    Karlsson, Thomas
    Linköping University, Department of Behavioural Sciences and Learning. Linköping University, Faculty of Arts and Sciences. Linköping University, Center for Medical Image Science and Visualization, CMIV.
    Landtblom, Anne-Marie
    Linköping University, Department of Clinical and Experimental Medicine, Neurology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Local Health Care Services in Central Östergötland, Department of Neurology. Östergötlands Läns Landsting, Local Health Care Services in the West of Östergötland, Department of Medical Specialist. Linköping University, Center for Medical Image Science and Visualization, CMIV.
    Lundberg, Peter
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics. Östergötlands Läns Landsting, Centre for Medical Imaging, Department of Radiology in Linköping.
    Engström, Maria
    Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Linköping University, Center for Medical Image Science and Visualization, CMIV.
    Right-hemispheric brain activation correlates to language performance2010In: NEUROIMAGE, ISSN 1053-8119, Vol. 49, no 4, p. 3481-3488Article in journal (Refereed)
    Abstract [en]

    Language function in the right-hemispheric homologues of Brocas and Wernickes areas does not only correlate with left-handedness or pathology, but occurs naturally in right-handed healthy subjects as well. In the current study, two non-invasive methods of assessing language lateralization are correlated with behavioral results in order to link hemispheric dominance to language ability in healthy subjects. Functional magnetic resonance imaging (fMRI) together with a sentence-completion paradigm was used to determine region-specific lateralization indices in the left- and right-sided Brocas and Wernickes areas, the frontal temporal lobe, the anterior cingulate cortex and the parietal lobe. In addition, dichotic listening results were used to determine overall language lateralization and to strengthen conclusions by correlating with fMRI indices. Results showed that fMRI lateralization in the superior parietal, the posterior temporal, and the anterior cingulate cortices correlated to dichotic listening. A decreased right ear advantage (REA), which indicates less left- hemispheric dominance in language, correlated with higher performance in most administered language tasks, including reading, language ability, fluency, and non-word discrimination. Furthermore, right hemispheric involvement in the posterior temporal lobe and the homologue of Brocas area suggests better performance in behavioral language tasks. This strongly indicates a supportive role of the right-hemispheric counterparts of Brocas and Wernickes areas in language performance.

  • 297.
    van Ettinger-Veenstra, Helene
    et al.
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences.
    Ragnehed, Mattias
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics UHL.
    McAllister, Anita
    Linköping University, Department of Clinical and Experimental Medicine, Speech and Language Pathology. Linköping University, Faculty of Health Sciences.
    Lundberg, Peter
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics UHL. Östergötlands Läns Landsting, Centre for Diagnostics, Department of Radiology in Linköping.
    Engström, Maria
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences.
    Right-hemispheric cortical contributions to language ability in healthy adults2012In: Brain and Language, ISSN 0093-934X, E-ISSN 1090-2155, Vol. 120, no 3, p. 395-400Article in journal (Refereed)
    Abstract [en]

    In this study we investigated the correlation between individual linguistic ability based on performance levels and their engagement of typical and atypical language areas in the brain. Eighteen healthy subjects between 21 and 64 years participated in language ability tests, and subsequent functional MRI scans measuring brain activity in response to a sentence completion and a word fluency task. Performance in both reading and high-level language tests correlated positively with increased right-hemispheric activation in the inferior frontal gyrus (specifically Brodmann area 47), the dorsolateral prefrontal cortex (DLPFC), and the medial temporal gyrus (Brodmann area 21). In contrast, we found a negative correlation between performance and left-hemispheric DLPFC activation.

    Our findings indicate that the right lateral frontal and right temporal regions positively modulate aspects of language ability.

  • 298. Vestad, Tor Arne
    et al.
    Gustafsson, Håkan
    Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Linköping University, Faculty of Health Sciences.
    Lund, Anders
    Linköping University, Department of Physics, Chemistry and Biology, Chemical Physics . Linköping University, The Institute of Technology.
    Hole, Eli Olaug
    Sagstuen, Einar
    Radiation-induced radicals in lithium formate monohydrate (LiHCO2·H2O). EPR and ENDOR studies of X-irradiated crystal and polycrystalline samples2004In: PCCP : physical chemistry chemical physics, ISSN 1463-9076, Vol. 6, p. 3017-3022Article in journal (Refereed)
    Abstract [en]

    Single crystals and polycrystalline samples of lithium formate monohydrate (HCO2Li·H2O) were X-irradiated at 295 K and studied using X-band EPR, ENDOR, and ENDOR-induced EPR (EIE) spectroscopy at 200 or 295 K. Two different radical species were observed. The overall dominating species is the CO2 radical trapped in the crystal matrix at an orientation not very different from that of the parent CO2 fragment in the unirradiated matrix. The g- and 13C hyperfine coupling tensors of the CO2 radical were determined. The large linewidth (about 1.5 mT) of the polycrystalline EPR spectrum is due to extensive hyperfine couplings with lithium ions and protons in the environment. Four lithium couplings and four proton couplings associated with the CO2 radical were measured, and all couplings were assigned to specific matrix nuclei. The spectra yield evidence for a second radical in low relative abundance. One small lithium hyperfine interaction detected was ascribed to this radical. Spectral simulations of the EPR and ENDOR spectra support the conclusions made.

  • 299.
    Vesterbacka, P
    et al.
    Radiation and Nuclear Safety Authority, Finland.
    Pettersson, Håkan
    Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics. Linköping University, Faculty of Health Sciences.
    Hanste, U-M
    Radiation and Nuclear Safety Authority, Finland.
    Jakobson, E
    Radiation Safety Department, Estonia.
    Kolstad, T
    Norwegian Radiation Protection Authority.
    Roos, P
    Riso National Laboratory.
    Östergren, I
    Swedish Radiation Safety Authority .
    Intercomparison of Rn-222 determination from groundwater2010In: Applied Radiation and Isotopes, ISSN 0969-8043, E-ISSN 1872-9800, Vol. 68, no 1, p. 214-218Article in journal (Refereed)
    Abstract [en]

    An intercomparison exercise on Rn-222 determination in groundwater was organized between eight Nordic laboratories. The individual laboratory results were in most cases within 20% of the median value and within reported uncertainties. Considering the particular difficulties in preparing, transporting and analyzing Rn-222, being a gaseous radionuclide, the results indicate a high analytical capability among the Nordic laboratories. In order to maintain a high analytical quality, similar intercomparisons will also be needed in the future.

  • 300.
    Vigren, Patrick
    et al.
    Linköping University, Department of Clinical and Experimental Medicine, Neurology. Linköping University, Faculty of Health Sciences. Linköping University, Department of Clinical and Experimental Medicine, Neurosurgery.
    Tisell, Anders
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics.
    Engström, Maria
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences.
    Karlsson, Thomas
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Behavioural Sciences and Learning, Disability Research. Linköping University, Faculty of Arts and Sciences.
    Dahlqvist Leinhard, Olof
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics.
    Lundberg, Peter
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Landtblom, Anne-Marie
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Clinical and Experimental Medicine, Neurology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Local Health Care Services in Central Östergötland, Department of Neurology.
    Low Thalamic NAA-Concentration Corresponds to Strong Neural Activation in Working Memory in Kleine-Levin Syndrome2013In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 8, no 2Article in journal (Refereed)
    Abstract [en]

    Background

    Kleine Levin Syndrome (KLS) is a rare disorder of periodic hypersomnia and behavioural disturbances in young individuals. It has previously been shown to be associated with disturbances of working memory (WM), which, in turn, was associated with higher activation of the thalamus with increasing WM load, demonstrated with functional magnetic resonance imaging (fMRI). In this study we aimed to further elucidate how these findings are related to the metabolism of the thalamus.

    Methods

    fMRI and magnetic resonance spectroscopy were applied while performing a WM task. Standard metabolites were examined: n-acetylaspartate (NAA), myo-inositol, choline, creatine and glutamate-glutamine. Fourteen KLS-patients and 15 healthy controls participated in the study. The patients with active disease were examined in asymptomatic periods.

    Results

    There was a statistically significant negative correlation between thalamic fMRI-activation and thalamic NAA, i.e., high fMRI-activation corresponded to low NAA-levels. This correlation was not seen in healthy controls. Thalamic levels of NAA in patients and controls showed no significant differences between the groups. None of the other metabolites showed any co-variation with fMRI-activiation.

    Conclusion

    This study shows negative correlation between NAA-levels and fMRI-activity in the left thalamus of KLS-patients while performing a WM task. This correlation could not be found in healthy control subjects, primarily interpreted as an effect of increased effort in the patient group upon performing the task. It might indicate a disturbance in the neuronal networks responsible for WM in KLS patients, resulting in higher effort at lower WM load, compared with healthy subjects. The general relationship between NAA and BOLD-signal is also discussed in the article.

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