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  • 201. Somsak, Dangtip
    et al.
    Atac, A
    Bergenwall, B
    Blomgren, J
    Elmgren, K
    Johansson, C
    Klug, J
    Olsson, Nils
    Alm Carlsson, Gudrun
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Söderberg, Jonas
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Facility for measurements of nuclear cross sections for fast neutron cancer therapy2000Ingår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 452, nr 3, s. 484-504Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A facility for measurements of neutron-induced double-differential light-ion production cross-sections, for application within, e.g., fast neutron cancer therapy, is described. The central detection elements are three-detector telescopes consisting of two silicon detectors and a CsI crystal. Use of ?E-?E-E techniques allows good particle identification for p, d, t, 3He and alpha particles over an energy range from a few MeV up to 100 MeV. Active plastic scintillator collimators are used to define the telescope solid angle. Measurements can be performed using up to eight telescopes at 20░ intervals simultaneously, thus covering a wide angular range. The performance of the equipment is illustrated using experimental data taken with a carbon target at En = 95 MeV. Distortions of the measured charged-particle spectra due to energy and particle losses in the target are corrected using a newly developed computer code. Results from such correction calculations are presented.

  • 202. Sparring Björkstén, Karin
    et al.
    Ekberg, Stefan
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Medicinsk radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Säfström, Pia
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Medicinsk radiologi. Östergötlands Läns Landsting, Bildmedicinskt centrum, Avdelningen för radiologi US.
    Dige, N
    Granerus, Göran
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Klinisk fysiologi. Östergötlands Läns Landsting, Hjärtcentrum, Fysiologiska kliniken.
    A computerized human reference brain for rCBF/SPET technetium-99m exametazime (HMPAO) investigation of elderly2004Ingår i: Clinical Physiology and Functional Imaging, ISSN 1475-0961, E-ISSN 1475-097X, Vol. 24, nr 4, s. 196-204Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Using the bull's eye approach, a reference brain from the single photon emission tomography (SPET) images of 10 subjects aged 62-81 years with excellent mental and physical health was constructed. SPET images were acquired twice, 1 week apart, using a single detector rotating gamma camera collecting 64 planar images over a 360° orbit. The centre of each transaxial slice was first defined with an automatic edge detecting algorithm applied to an anterior-posterior and a side profile of the brain. Each slice was divided into 40 sectors. Maximum counts/pixel in each sector was picked. The 40 maximum count values from one transaxial slice were allowed to form a horizontal row in a new parametric image on the x-axis and slice number from the vertex to the basal parts of the brain on the y-axis. This new image was scaled to a 64 × 16 pixel matrix by interpolation, which meant a normalization of all studies to the same size. The parametric image in each subject was scaled with regard to intensity by a factor calculated by a normalization procedure using the least squares analysis. Mean and SD for each pixel were calculated, thereby constructing a 'mean parametric image', and a 'SD parametric image'. These two images are meant to be used as the reference brain for evaluation of patient studies. This method can be used for objective measurements of diffuse brain changes and for pattern recognition in larger groups of patients. Statistical multifactorial analysis of parameters used for acquisition and data processing is possible. © 2004 Blackwell Publishing Ltd.

  • 203.
    Stark, K.
    et al.
    Department of Systems Ecology, Stockholm University, Stockholm 106 91, Sweden.
    Pettersson, Håkan
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    External radiation doses from 137Cs to frog phantoms in a wetland area: In situ measurements and dose model calculations2008Ingår i: Radiation and Environmental Biophysics, ISSN 0301-634X, E-ISSN 1432-2099, Vol. 47, nr 4, s. 481-489Artikel i tidskrift (Refereegranskat)
    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.

  • 204.
    Stark, Karolina
    et al.
    Stockholm University .
    Pettersson, Håkan B L
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Response to "On the calculation of external radiation doses from Cs-137 to frog phantoms in a wetland area" by G. Prohl and A. Ulanovsky2009Ingår i: RADIATION AND ENVIRONMENTAL BIOPHYSICS, ISSN 0301-634X, Vol. 48, nr 2, s. 245-246Artikel i tidskrift (Övrigt vetenskapligt)
  • 205.
    Stenström, Mats
    et al.
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
    Olander, Birger
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
    Carlsson, Carl A.
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
    Alm Carlsson, Gudrun
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Håkanson, Rolf
    Department of Pharmacology, University of Lund, Lund, Sweden.
    Methodologic aspects of computed microtomography to monitor the development of osteoporosis in gastrectomized rats1995Ingår i: Academic Radiology, ISSN 1076-6332, Vol. 2, nr 9, s. 785-791Artikel i tidskrift (Refereegranskat)
    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.

  • 206.
    Stenström, Mats
    et al.
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
    Olander, Birger
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
    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
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Bone mineral density and bone structure parameters as predictors of bone strength: an analysis using computerized microtomography and gastrectomy-induced osteopenia in the rat2000Ingår i: Journal of Biomechanics, ISSN 0021-9290, Vol. 33, nr 3, s. 289-297Artikel i tidskrift (Refereegranskat)
    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.

  • 207.
    Söderberg, Jonas
    et al.
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
    Alm Carlsson, Gudrun
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Fast neutron absorbed dose distributions in the energy range 0.5-80 MeV: a Monte Carlo study2000Ingår i: Physics in Medicine and Biology, ISSN 0031-9155, E-ISSN 1361-6560, Vol. 45, nr 10, s. 2987-3007Artikel i tidskrift (Refereegranskat)
    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.

  • 208.
    Söderberg, Jonas
    et al.
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
    Alm Carlsson, Gudrun
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Ahnesjö, Anders
    Nucletron Scandinavia AB, Uppsala, Sweden.
    Monte Carlo evaluation of a photon pencil kernel algorithm applied to fast neutron therapy treatment planning2003Ingår i: Physics in Medicine and Biology, ISSN 0031-9155, Vol. 48, nr 20, s. 3327-3344Artikel i tidskrift (Refereegranskat)
    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.

  • 209.
    Söderberg, Jonas
    et al.
    Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Linköpings universitet, Hälsouniversitetet.
    Dangtip, Somsak
    Department of Neutron Research, Uppsala University, Uppsala, Sweden.
    Alm Carlsson, Gudrun
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    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 methods2002Ingår i: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, ISSN 0168-583X, E-ISSN 1872-9584, Vol. 195, nr 3-4, s. 426-434Artikel i tidskrift (Refereegranskat)
    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.

  • 210.
    Söderberg, Jonas
    et al.
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Radiofysik.
    Pettersson, Håkan
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Katastrofer orsakade av joniserande strålning2002Ingår i: Katastrofmedicin / [ed] Sten Lennquist, Linköping: Linköpings universitet , 2002, 2, s. 303-318Kapitel i bok, del av antologi (Övrigt vetenskapligt)
    Abstract [sv]

    Denna bok beskriver hur man ska hantera den svåra uppgiften att bedriva sjukvård på effektivast möjliga sätt i alla de olika typer av situationer där det akuta vårdbehovet överstiger vad som kan klaras med tillgängliga resurser. Den täcker hela omhändertagandekedjan från skadeområdet till definitiv behandling på sjukhus. Denna nya upplaga av Katastrofmedicin är en helt ny bok, utökad till innehållet och uppdaterad mot bakgrund av den omfattande utveckling som präglat detta ämnesområde sedan föregående upplaga.

    Katastrofmedicin kan användas som både läromedel vid utbildning på alla nivåer och som en lättillgänglig handbok och vänder sig till såväl personal i prehospital vård som till läkare och sjuksköterskor på sjukhusens akutmottagningar och inom berörda specialiteter.

  • 211. Tapiovaara, M
    et al.
    Sandborg, Michael
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Medicinsk radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    How should low-contrast detail detectability be measured in fluoroscopy?2004Ingår i: Medical physics (Lancaster), ISSN 0094-2405, Vol. 31, nr 9, s. 2564-2576Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The relationship and precision of four methods for measuring the low-contrast detail detectability in fluoroscopic imaging were studied. These included the physical measurement of the accumulation rate of the square of the signal-to-noise ratio (SNRrate2), two-alternative forced-choice (2-AFC) experiments, sixteen-alternative forced-choice (16-AFC) experiments and subjective determination of the threshold contrast. The precision and sensitivity of the threshold contrast measurement were seen to be modest in the constancy testing of fluoroscopic equipment: only large changes in system performance could be reliably detected by that method. The measurement of the SNRrate2 is suggested instead. The relationship between the results of the various methods were studied, and it was found that human performance can be related to SNRrate2 by introducing the concept of the effective image information integration time (teff). When measured for an unlimited observation time, it depicts the saturation of human performance in detecting a static low-contrast detail in dynamic image noise. Here, teff was found to be about 0.6 s in 2-AFC tests and 0.3 s in 16-AFC tests. © 2004 American Association of Physicists in Medicine.

  • 212.
    Tapiovaara, Markku
    et al.
    Finnish Centre for Radiat. & Nucl. Safety.
    Sandborg, Michael
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen. Linköpings universitet, Hälsouniversitetet.
    Evaluation of image quality in fluoroscopy by measurements and Monte Carlo calculations1995Ingår i: Physics in Medicine and Biology, ISSN 0031-9155, E-ISSN 1361-6560, Vol. 40, nr 4, s. 589-607Artikel i tidskrift (Refereegranskat)
    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.

  • 213.
    Tapiovaara, Markku
    et al.
    n/a.
    Servomaa, Antti
    n/a.
    Sandborg, Michael
    Linköpings universitet, Institutionen för medicin och vård, Medicinsk radiofysik. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen. Linköpings universitet, Hälsouniversitetet.
    Dance, David
    n/a.
    Optimizing the imaging conditions in paediatric fluoroscopy2000Ingår i: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 90, nr 1-2, s. 211-216Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Patient dose and image quality were studied in paediatric fluoroscopy. The study consisted of two parts: theoretical calculation of optimal imaging conditions by the Monte Carlo method and clinical measurements of dose rate and SNR2rate at six hospitals. For many imaging tasks the most efficient imaging technique in fluoroscopy is obtained by using high filtration, relatively low X ray tube potential and a fibre-interspaced and -covered grid for all but the smallest patients and X ray field sizes. The clinical measurements supported our theoretical results and revealed a notable variation in image quality and dose rate among the hospitals studied. Notable patient dose rate reduction seems possible in paediatric fluoroscopy by adjusting the equipment to work with more efficient imaging factors and a low image receptor input dose rate.

  • 214.
    Thilander Klang, Anne
    et al.
    Department of Medical Physics and Biomedical Engineering, Sahlgrenska University Hospital, SE-413 45.
    Helmrot, Ebba
    Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen. Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiologi. Linköpings universitet, Hälsouniversitetet.
    METHODS OF DETERMINING THE EFFECTIVE DOSE INDENTAL RADIOLOGY2010Ingår i: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 139, nr 1-3, s. 306-309Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A wide variety of X-ray equipment is used today in dental radiology, including intra-oral, orthopantomographic, cephalometric, cone-beam computed tomography (CBCT) and computed tomography (CT). This raises the question of how the radiation risks resulting from different kinds of examinations should be compared. The risk to the patient is usually expressed in terms of the effective dose. However, it is difficult to determine its reliability, and it is difficult to make comparisons, especially when different modalities are used. The classification of the new CBCT units is also problematic as they are sometimes classified as CT units. This will lead to problems in choosing the best dosimetric method, especially when the examination geometry more resembles an ordinary orthopantomographic examination, as the axis of rotation is not at the centre of the patient, and small radiation field sizes are used. The purpose of this study was to present different methods for the estimation of the effective dose from the equipment currently used in dental radiology, and to discuss their limitations. The methods are compared based on common used measurable and computable dose quantities, and their reliability in the estimation of effective dose.

  • 215. Tingberg, A
    et al.
    Båth, M
    Håkansson, M
    Medin, J
    Besjakov, J
    Sandborg, Michael
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Medicinsk radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Alm-Carlsson, Gudrun
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Medicinsk radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Mattsson, S
    Månsson, LG
    Evaluation of image quality of lumbar spine images: A comparison between FFE and VGA2005Ingår i: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 114, nr 1-3, s. 53-61Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Purpose: The aim of the present study is to compare two different methods for evaluation of the quality of clinical X-ray images. Methods: Based on fifteen lumbar spine radiographs, two new sets of images were created. A hybrid image set was created by adding two distributions of artificial lesions to each original image. The image quality parameters spatial resolution and noise were manipulated and a total of 210 hybrid images were created. A set of 105 disease-free images was created by applying the same combinations of spatial resolution and noise to the original images. The hybrid images were evaluated with the free-response forced error experiment (FFE) and the normal images with visual grading analysis (VGA) by nine experienced radiologists. Results: In the VGA study, images with low noise were preferred over images with higher noise levels. The alteration of the MTF had a limited influence on the VGA score. For the FFE study, the visibility of the lesions was independent of the sharpness and the noise level. No correlation was found between the two image quality measures. Conclusions: FFE is a precise method for evaluation of image quality, but the results are only valid for the type of lesion used in the study, whereas VGA is a more general method for clinical image quality assessment. The results of the FFE study indicate that there might be a potential to lower the dose levels in lumbar spine radiography without losing important diagnostic information. © The Author 2005. Published by Oxford University Press. All rights reserved.

  • 216. Tingberg, A
    et al.
    Båth, M
    Håkansson, M
    Medin, J
    Sandborg, Michael
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Medicinsk radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Alm-Carlsson, Gudrun
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Medicinsk radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Mattsson, S
    Gunnar Månsson, L
    Comparison of two methods for evaluation of image quality of lumbar spine radiographs2004Ingår i: SPIE Proc Jfr 2001 Preceedings of SPIE ISSN 1605-7422, ISSN 1017-2653, Vol. 5372Artikel i tidskrift (Refereegranskat)
  • 217. Tingberg, A
    et al.
    Eriksson, F
    Medin, J
    Besjakov, J
    Båth, M
    Håkansson, M
    Sandborg, Michael
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Medicinsk radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Almen, A
    Alm-Carlsson, Gudrun
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Medicinsk radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Mattsson, S
    Månsson, LG
    Inter-observer variation in masked and unmasked images for quality evaluation of clinical radiographs2005Ingår i: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 114, nr 1-3, s. 62-68Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Purpose: To investigate the influence of masking on the inter-observer variation in image quality evaluation of clinical radiographs of chest and lumbar spine. Background: Inter-observer variation is a big problem in image quality evaluation since this variation is often much bigger than the variation in image quality between, for example, two radiographic systems. In this study, we have evaluated the effect of masking on the inter-observer variation. The idea of the masking was to force every observer to view exactly the same part of the image and to avoid the effect of the overall 'first impression' of the image. A discussion with a group of European expert radiologists before the study indicated that masking might be a good way to reduce the inter-observer variation. Methods: Five chest and five lumbar spine radiographs were collected together with detailed information regarding exposure conditions. The radiographs were digitised with a high-performance scanner and five different manipulations were performed, simulating five different exposure conditions. The contrast, noise and spatial resolution were manipulated by this method. The images were printed onto the film and the individual masks were produced for each film, showing only the parts of the images that were necessary for the image quality evaluation. The quality of the images was evaluated on ordinary viewing boxes by a large group of experienced radiologists. The images were examined with and without the masks with a set of image criteria (if fulfilled, 1 point, and not fulfilled, 0 point), and the mean score was calculated for each simulated exposure condition. Results: The results of this study indicate that - contrary to what was supposed - the inter-observer variation increased when the images were masked. In some cases, especially for chest, this increase was statistically significant. Conclusions: Based on the results of this study, image masking in studies of fulfilment of image criteria cannot be recommended. © The Author 2005. Published by Oxford University Press. All rights reserved.

  • 218. Tingberg, A
    et al.
    Herrmann, C
    Lanhede, B
    Almen, A
    Sandborg, Michael
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Medicinsk radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    McVey, G
    Mattsson, S
    Panzer, W
    Besjakov, J
    Månsson, LG
    Kheddache, S
    Alm-Carlsson, Gudrun
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Medicinsk radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Dance, DR
    Tylen, U
    Zankl, M
    Influence of the characteristic curve on the clinical image quality of lumbar spine and chest radiographs2004Ingår i: British Journal of Radiology, ISSN 0007-1285, E-ISSN 1748-880X, Vol. 77, nr 915, s. 204-215Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The "European Guidelines on Quality Criteria for Diagnostic Radiographic Images" do not address the choice of the film characteristic (H&D) curve, which is an important parameter for the description of a radiographic screen-film system. The image contrast of clinical lumbar spine and chest radiographs was altered by digital image processing techniques, simulating images with different H&D curves, both steeper and flatter than the original. The manipulated images were printed on film for evaluation. Seven experienced radiologists evaluated the clinical image quality by analysing the fulfilment of the European Image Criteria (ICS) and by visual grading analysis (VGA) of in total 224 lumbar spine and 360 chest images. A parallel study of the effect of the H&D curve has also been made using a theoretical model. The contrast (ΔOD) of relevant anatomical details was calculated, using a Monte Carlo simulation-model of the complete imaging system including a 3D voxel phantom of a patient. Correlations between the calculated contrast and the radiologists' assessment by VGA were sought. The results of the radiologists' assessment show that the quality in selected regions of lumbar spine and chest images can be significantly improved by the use of films with a steeper H&D curve compared with the standard latitude film. Significant (p<0.05) correlations were found between the VGA results and the calculations of the contrast of transverse processes and trabecular details in the lumbar spine vertebrae, and with the contrast of blood vessels in the retrocardiac area of the chest.

  • 219.
    Tisell, Anders
    et al.
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV.
    Dahlqvist Leinhard, Olof
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
    Warntjes, Marcel, Jan Bertus
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och hälsa, Klinisk fysiologi. Östergötlands Läns Landsting, Hjärtcentrum, Fysiologiska kliniken. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV.
    Engström, Maria
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiologi. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV.
    Landtblom, Anne-Marie
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för klinisk och experimentell medicin. Östergötlands Läns Landsting, Närsjukvården i centrala Östergötland, Neurologiska kliniken. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV.
    Lundberg, Peter
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen. Östergötlands Läns Landsting, Bildmedicinskt centrum, Röntgenkliniken i Linköping.
    Absolute quantification of LCModel water scaled metabolite concentration of 1H magnetic resonance spectroscopy (MRS) using quantitative magnetic resoonance imaging (qMRI)2008Ingår i: ESMRMB,2008, 2008Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

      

  • 220.
    Tisell, Anders
    et al.
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV.
    Engström, Maria
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiologi. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV.
    Karlsson, Thomas
    Linköpings universitet, Filosofiska fakulteten. Linköpings universitet, Institutionen för beteendevetenskap och lärande. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV.
    Vigren, Patrik
    NSC.
    Dahlqvist Leinhard, Olof
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
    Lundberg, Peter
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen. Östergötlands Läns Landsting, Bildmedicinskt centrum, Röntgenkliniken i Linköping.
    Etiology of periodic hypersomnia explored by combined functional and molecular neuroimaging methods2008Ingår i: World Molecular Imaging Conference,,2008, 2008Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

      

  • 221. Togowa, O
    et al.
    Povinec, PP
    Pettersson, Håkan
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Collective dose estimates by the marine food pathway from liquid radioactive wastes dumped in the sea of Japan.1999Ingår i: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 237, s. 241-248Artikel i tidskrift (Refereegranskat)
  • 222.
    Ullman, Gustaf
    et al.
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
    Dance, David R.
    Royal Surrey County Hospital, Guildford.
    Sandborg, Michael
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Alm Carlsson, Gudrun
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Svalkvist, Angelica
    University of Gothenburg.
    Båth, Magnus
    University of Gothenburg.
    A Monte Carlo-based model for simulation of digital chest tomosynthesis2010Ingår i: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 139, nr 1-3, s. 159-163Artikel i tidskrift (Refereegranskat)
    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.

    Ladda ner fulltext (pdf)
    FULLTEXT01
  • 223.
    Ullman, Gustaf
    et al.
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Medicinsk radiofysik.
    Sandborg, Michael
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Medicinsk radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Dance, D
    Hunt, R
    Alm-Carlsson, Gudrun
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Medicinsk radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    The influence of patient thickness and imaging system on patient dose and physical image quality in digital chest imaging2005Ingår i: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 114, nr 1-3, s. 294-297Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The aim of this work was to study the influence of patient thickness, tube voltage and image detector on patient dose, contrast and ideal observer signal-to-noise ratio (SNRI), for pathological details positioned at different regions in the image in posterior-anterior (PA) chest radiology. A Monte Carlo computational model was used to compute measures of physical image quality (contrast, SNRI) and patient effective dose, E. Two metastasis-like details positioned in the central right lung and right lung near the spine, respectively, were studied. The tube voltage was varied between 100 and 150 kV and the patient thickness between 20 and 28 cm. Both, a computed radiography (CR) system and a direct radiography (DR) system, were investigated. The DR system provides both lower doses and better image quality compared with the CR system. The SNRI2/E is ∼2.9 times higher for the DR system compared with the CR system. © The Author 2005. Published by Oxford University Press. All rights reserved.

  • 224.
    Ullman, Gustav
    et al.
    Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Linköpings universitet, Hälsouniversitetet.
    Sandborg, Michael
    Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Alm Carlsson, Gudrun
    Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Validation of Voxman Monte Carlo code and calibration for digital systems2003Rapport (Övrigt vetenskapligt)
    Abstract [en]

    The objective of this work was to test the Monte Carlo model ‘Voxman’ against measurements on x-ray systems in the clinic. X-ray transmission experiments are performed to test of the accuracy of the Monte Carlo photon transport. Experiments were also performed with an image plate (CR) system in the clinic to compare the measured pixel values with calculated pixel values. Measurements were also performed with the automatic exposure control (AEC) chambers used in Linköping and Motala. The purpose for those measurements was to choose a normalisation of the entrance surface dose.

    Ladda ner fulltext (pdf)
    Validation of Voxman Monte Carlo code and calibration for digital systems
  • 225.
    Ullman, Gustav
    et al.
    Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Linköpings universitet, Hälsouniversitetet.
    Sandborg, Michael
    Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Dance, David R
    Department of Physics, The Royal Marsden NHS Trust, UK.
    Båth, M.
    Department of Radiation Physics, Göteborg, Sweden.
    Håkansson, M.
    Department of Radiation Physics, Göteborg, Sweden.
    Börjesson, S.
    Department of Radiation Physics, Göteborg, Sweden.
    Hunt, Roger
    Department of Physics, The Royal Marsden NHS Trust, UK.
    Alm Carlsson, Gudrun
    Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    On the extent of quantum noise limitation in digital chest radiography2004Rapport (Övrigt vetenskapligt)
    Abstract [en]

    The aim for this work was to study to what extent the detection of nodules is quantum noise limited, based on the combined results from a nodule-detection clinical trial and a Monte Carlo computational model of a digital chest imaging system. The Monte Carlo computer program computes measures of physical image quality such as image contrast, C and signalto-noise ratio, SNR for nodules of any size. A computed radiography (CR) imaging system used simulated. The patient anterior-posterior thickness was 25 cm and nodules with diameters between 1-40 mm were included. The image contrast and SNR was calculated for 1600 (40x40) positions in the chest image and averaged over five anatomical regions of interest (lateral pulmonary, retrocardial, hilar, lower- and upper mediastinal regions). Threshold contrasts for each region, Cth, corresponding to Az=0.80 for detecting a 10 mm nodule, were deduced from the clinical trial. A threshold is also used for the quantum noise signal-to-noise ratio, SNRth. The model computes the diameter of a disk-shaped object that is required to comply with the two criteria: SNR≥SNRth and C≥Cth. A system is said to be quantum noise limited when the nodule size required to fulfil both criteria is not limited by the contrast but by the SNR. The required nodule diameter is largest in the hilar region (25 mm) and smallest in the lateral pulmonary region (11 mm). When the threshold SNRth=25 is used, the lower mediastinal region is quantum noise limited already at low speed classes (S>100). The hilar region is never quantum noise limited at realistic speed classes (S<1000). The accuracy of this model will be tested in the future by more sophisticated modelling of anatomical background and noise in the SNR-expression.

    Ladda ner fulltext (pdf)
    On the extent of quantum noise limitation in digital chest radiography
  • 226.
    Ullman, Gustav
    et al.
    Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Linköpings universitet, Hälsouniversitetet.
    Sandborg, Michael
    Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Dance, David R
    Department of Physics, The Royal Marsden NHS Trust, UK.
    Hunt, Roger
    Department of Physics, The Royal Marsden NHS Trust, UK.
    Alm Carlsson, Gudrun
    Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Distributions of scatter-to-primary ratios in chest PA radiography using grid or air gap for scatter-rejection2004Rapport (Övrigt vetenskapligt)
    Abstract [en]

    The aim for this work was to calculate distributions of scatter-to-primary ratios (εs/εp) and signal-to-noise ratios per pixel (SNRp) for a large set of imaging systems with either grid or air gap for scatter rejection. Grids with ratio 8-16 and air gap length 20 and 40 cm were used. The tube voltage was varied between 90-150 kV and three patient thickness between 20-28 cm were tested in order to compare scatter-rejections techniques for different conditions. Distributions of this sort may provide useful information on how physical image quality (contrast, SNR) is distributed over the chest PA image. A Monte Carlo computer program was used for the calculations, including a model of both the patient (voxel phantom) and the imaging system. The mean value of the εs/εp is 0.39 in the hilar region and 1.72 in the lower mediastinal region. For a 28 cm patient, the corresponding values are 0.42 in the hilar region and 2.58 in the lower mediastinal region. The grid with ratio 16 is the most efficient scatter rejection technique in all regions except the hilar region. In the hilar region, the most efficient technique is the 40 cm air gap.

    Ladda ner fulltext (pdf)
    Distributions of scatter-to-primary ratios in chest PA radiography using grid or air gap for scatter-rejection
  • 227.
    Ullman, Gustav
    et al.
    Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Linköpings universitet, Hälsouniversitetet.
    Sandborg, Michael
    Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Dance, David R
    Department of Physics, The Royal Marsden NHS Trust, UK.
    Hunt, Roger
    Department of Physics, The Royal Marsden NHS Trust, UK.
    Alm Carlsson, Gudrun
    Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Optimisation of chest radiology by computer modelling of image quality measures and patient effective dose2004Rapport (Övrigt vetenskapligt)
    Abstract [en]

    A set of modelled computed radiography (CR) systems are compared with a reference system. Calculations are performed, which compares the effective dose and a set of figures of merit corresponding to the image quality of both the modelled systems and the reference system. For a nodule with soft tissue corresponding, the signal-to-noise ratio, SNR, is found to decrease with increasing tube voltage. On the other hand, the ratio of the contrast of the nodule compared to the contrast of a rib (nodule-to-rib contrast-ratio) is found to increase with increasing tube voltage.

    Ladda ner fulltext (pdf)
    Optimisation of chest radiology by computer modelling of image quality measures and patient effective dose
  • 228.
    Ullman, Gustav
    et al.
    Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Linköpings universitet, Hälsouniversitetet.
    Sandborg, Michael
    Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Hunt, Roger
    Department of Physics, The Royal Marsden NHS Trust, UK.
    Dance, David R
    Department of Physics, The Royal Marsden NHS Trust, UK.
    Alm Carlsson, Gudrun
    Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Implementation of pathologies in the Monte Carlo model in chest and breast imaging2003Rapport (Övrigt vetenskapligt)
    Abstract [en]

    The Monte Carlo simulation model of the chest and breast imaging systems including a voxelised model of the patient are used to compute measures of image quality and patient absorbed dose. It is important that the model computes measures of image quality of pathological details that are similar in size, composition and position as real pathological details in typical chest and breast images. Moreover, the other partners of the co-coordinated research project will produce hybrid images with pathological details and have these images assessed by a group of radiologist. The model will then be used to study to what extent variations in clinical image quality can be explained by variations in physical image quality, for example signal-to-noise ratio. This report summarizes the selection of pathological details to include in the model of chest and breast imaging systems.

    Ladda ner fulltext (pdf)
    Implementation of pathologies in the Monte Carlo model in chest and breast imaging
  • 229.
    Ullman, Gustav
    et al.
    Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Linköpings universitet, Hälsouniversitetet.
    Sandborg, Michael
    Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Tingberg, Anders
    Department of Radiation Physics, Malmö University Hospital, Sweden.
    Dance, David R
    Department of Physics, The Royal Marsden NHS Trust, UK.
    Hunt, Roger
    Department of Physics, The Royal Marsden NHS Trust, UK.
    Alm Carlsson, Gudrun
    Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Comparison of clinical and physical measures of image quality in chest PA and pelvis AP views at varying tube voltages2004Rapport (Övrigt vetenskapligt)
    Abstract [en]

    Image quality in digital chest PA and pelvis AP was assessed using two different methods; one based on observations of images of an anthropomorphic phantom, one based on computer modelling 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 approximately the same effective dose was achieved in the modelled patient (anthropomorphic phantom). Two x-ray units were employed using a digital image detector (computed radiography, CR, system) with standard tube filtration and anti-scatter 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 the computer model in terms of the signal-to-noise ratio, SNR for fixed effective dose in the voxel phantom. The computer model uses Monte Carlo simulations of the patient and complete imaging system. Both the VGAS (visual grading analysis score) and SNR increase with decreasing tube voltage in both chest PA and pelvis AP examinations, indicating superior performance if lower tube voltages than used today are employed in digital radiology. 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 analogue screen-film radiography are discussed as well as the relevance of using VGAS and quantum noise SNR as measures of image quality.

    Ladda ner fulltext (pdf)
    Comparison of clinical and physical measures of image quality in chest PA and pelvis AP views at varying tube voltages
  • 230.
    van Ettinger-Veenstra, Helene M
    et al.
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiologi. Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV.
    Ragnehed, Mattias
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiologi. Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV.
    Hällgren, Mathias
    Linköpings universitet, Institutionen för klinisk och experimentell medicin, Teknisk audiologi. Linköpings universitet, Hälsouniversitetet.
    Karlsson, Thomas
    Linköpings universitet, Institutionen för beteendevetenskap och lärande. Linköpings universitet, Filosofiska fakulteten. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV.
    Landtblom, Anne-Marie
    Linköpings universitet, Institutionen för klinisk och experimentell medicin, Neurologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Närsjukvården i centrala Östergötland, Neurologiska kliniken. Östergötlands Läns Landsting, Närsjukvården i västra Östergötland, Medicinska specialistkliniken . Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV.
    Lundberg, Peter
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen. Östergötlands Läns Landsting, Bildmedicinskt centrum, Röntgenkliniken i Linköping.
    Engström, Maria
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiologi. Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV.
    Right-hemispheric brain activation correlates to language performance2010Ingår i: NEUROIMAGE, ISSN 1053-8119, Vol. 49, nr 4, s. 3481-3488Artikel i tidskrift (Refereegranskat)
    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.

    Ladda ner fulltext (pdf)
    FULLTEXT01
  • 231.
    Vesterbacka, P
    et al.
    Radiation and Nuclear Safety Authority, Finland.
    Pettersson, Håkan
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen. Linköpings universitet, Hälsouniversitetet.
    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 groundwater2010Ingår i: Applied Radiation and Isotopes, ISSN 0969-8043, E-ISSN 1872-9800, Vol. 68, nr 1, s. 214-218Artikel i tidskrift (Refereegranskat)
    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.

  • 232. Vogel, HJ
    et al.
    Lundberg, Peter
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Bagh, K
    Non-invasive NMR studies of metabolism in cultures Cathranthus roses cells (Invited rewiew)1999Ingår i: In vitro Cellular & Developmental Biology-Animal, ISSN 1071-2690, E-ISSN 1543-706X, Vol. 35, s. 144-151Artikel i tidskrift (Refereegranskat)
  • 233.
    Wallin, Anders
    et al.
    Sahlgrenska University Hospital.
    Ekberg, Stefan
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Lind, K
    Sahlgrenska University Hospital.
    Milos, V
    Sahlgrenska University Hospital.
    Granérus, Ann-Kathrine
    Linköpings universitet, Institutionen för klinisk och experimentell medicin, Geriatrik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Närsjukvården i centrala Östergötland, Geriatriska kliniken.
    Granerus, Göran
    Linköpings universitet, Institutionen för medicin och hälsa, Klinisk fysiologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Hjärtcentrum, Fysiologiska kliniken.
    Posterior cortical brain dysfunction in cognitively impaired patients with Parkinson´s disease - an rCBF scintigraphy study2007Ingår i: Acta Neurologica Scandinavica, ISSN 0001-6314, E-ISSN 1600-0404, Vol. 116, nr 6, s. 347-354Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Objectives: The aim of the study was to visualize cortical function in Parkinson's patients with various degrees of cognitive impairment.

    Materials and methods: Thirty-seven patients with Parkinson's disease and three with Parkinson plus syndromes underwent cognitive assessment and rCBF using 99mTC-HMPAO-SPECT.

    Results: Almost no regional reductions in cerebral blood flow were seen in patients without cognitive impairment (n = 16). Limited, mainly posterior, blood flow reductions were seen in patients with mild cognitive impairment (n = 14), whereas the reductions were extensive and bilaterally symmetric, involving both anterior and posterior brain regions in patients with dementia (n = 10).

    Conclusions: The findings suggest a widespread cortical, mainly posterior type of dysfunction and a relationship between the degree of cognitive impairment and the magnitude of the dysfunction.

  • 234.
    Warntjes, Marcel, Jan Bertus
    et al.
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och hälsa, Klinisk fysiologi. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Östergötlands Läns Landsting, Hjärtcentrum, Fysiologiska kliniken.
    Dahlqvist, Olof
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV.
    West, Janne
    Linköpings universitet, Institutionen för medicin och hälsa, Avdelningen för radiologiska vetenskaper. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Hälsouniversitetet.
    Lundberg, Peter
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen. Östergötlands Läns Landsting, Bildmedicinskt centrum, Röntgenkliniken i Linköping.
    Rapid magnetic resonance quantification on the brain: Optimization for clinical usage2008Ingår i: Magnetic Resonance in Medicine, ISSN 0740-3194, E-ISSN 1522-2594, Vol. 60, nr 2, s. 320-329Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A method is presented for rapid simultaneous quantification of the longitudinal T1 relaxation, the transverse T2 relaxation, the proton density (PD), and the amplitude of the local radio frequency B 1 field. All four parameters are measured in one single scan by means of a multislice, multiecho, and multidelay acquisition. It is based on a previously reported method, which was substantially improved for routine clinical usage. The improvements comprise of the use of a multislice spin-echo technique, a background phase correction, and a spin system simulation to compensate for the slice-selective RF pulse profile effects. The aim of the optimization was to achieve the optimal result for the quantification of magnetic resonance parameters within a clinically acceptable time. One benchmark was high-resolution coverage of the brain within 5 min. In this scan time the measured intersubject standard deviation (SD) in a group of volunteers was 2% to 8%, depending on the tissue (voxel size = 0.8 x 0.8 x 5 mm). As an example, the method was applied to a patient with multiple sclerosis in whom the diseased tissue could clearly be distinguished from healthy reference values. Additionally it was shown that, using the approach of synthetic MRI, both accurate conventional contrast images as well as quantification maps can be generated based on the same scan. © 2008 Wiley-Liss, Inc.

  • 235.
    Wigström, Lars
    et al.
    Linköpings universitet, Institutionen för medicin och vård, Klinisk fysiologi. Linköpings universitet, Hälsouniversitetet.
    Lindström, Lena
    Linköpings universitet, Institutionen för medicin och hälsa, Klinisk fysiologi. Linköpings universitet, Hälsouniversitetet.
    Sjöqvist, Lars
    Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen. Linköpings universitet, Hälsouniversitetet.
    Thuomas, K. Å.
    Linköpings universitet, Institutionen för medicin och vård, Radiologi. Linköpings universitet, Hälsouniversitetet.
    Wranne, Bengt
    Linköpings universitet, Institutionen för medicin och hälsa, Klinisk fysiologi. Linköpings universitet, Hälsouniversitetet.
    M-mode magnetic resonance imaging: a new modality for assessing cardiac function1995Ingår i: Clinical Physiology, ISSN 0144-5979, E-ISSN 1365-2281, Vol. 15, nr 4, s. 397-407Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Magnetic resonance imaging (MRI) studies of the heart have been used for some years, but there are few tools available to quantify cardiac motion. A method has been developed that creates an M-mode MRI image, analogous to the one used in echocardiography, to display motion along a line as a function of time. The M-mode image is created from MRI images acquired with an ordinary gradient echo cine sequence. In a cinematographic display of the images, a cursor line can be positioned in order to determine the orientation of the measurement. A resampling algorithm then calculates the appearance of the M-mode image along the cursor line. The MRI method has been compared to echocardiographic M-mode in a phantom study and by measuring mitral and tricuspid annulus motion in 20 normal subjects. The phantom study showed no significant differences between MRI and echocardiographic M-mode measurements (difference mm). The annulus motion exhibits a similar pattern using both methods and the measured amplitudes are in close agreement. M-mode MRI provides similar information to echocardiography, but the cursor line can be placed arbitrarily within the image plane and the method is thus not limited to certain acoustic windows. This makes M-mode MRI a promising technique for assessing cardiac motion.

  • 236.
    Wigström, Lars
    et al.
    Linköpings universitet, Institutionen för medicin och vård, Klinisk fysiologi. Linköpings universitet, Hälsouniversitetet.
    Sjöqvist, Lars
    Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen. Linköpings universitet, Hälsouniversitetet.
    Wranne, Bengt
    Linköpings universitet, Institutionen för medicin och vård, Klinisk fysiologi. Linköpings universitet, Hälsouniversitetet.
    Temporally resolved 3D phase-contrast imaging1996Ingår i: Magnetic Resonance in Medicine, ISSN 0740-3194, E-ISSN 1522-2594, Vol. 36, nr 5, s. 800-803Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A conventional 3D phase contrast acquisition generates images with good spatial resolution, but often gives rise to artifacts due to pulsatile flow. 2D cine phase contrast, on the other hand, can register dynamic flow, but has a poor spatial resolution perpendicular to the imaging plane. A combination of both high spatial and temporal resolution may be advantageous in some cases, both in quantitative flow measurements and in MR angiography. The described 3D cine phase contrast pulse sequence creates a temporally resolved series of 3D data sets with velocity encoded data.

  • 237. Williamsson, JF
    et al.
    Dempsey, JF
    Kirov, AS
    Monroe, JI
    Binns, WR
    Hedtjärn, Håkan
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Plastic scintillator response to low-energy photons1999Ingår i: Physics in Medicine and Biology, ISSN 0031-9155, E-ISSN 1361-6560, Vol. 44, s. 857-871Artikel i tidskrift (Övrig (populärvetenskap, debatt, mm))
  • 238. Wise, K N
    et al.
    Sandborg, Michael
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Radiofysik.
    Persliden, J
    Alm Garlsson, Gudrun
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Sensitivity of coefficients for converting entrance surface dose and kerma-area product to effective dose and energy imparted to the patient.1999Ingår i: Physics in Medicine and Biology, ISSN 0031-9155, E-ISSN 1361-6560, Vol. 44, s. 1937-1954Artikel i tidskrift (Övrig (populärvetenskap, debatt, mm))
2345 201 - 238 av 238
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