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  • 101.
    Gårdestig, Magnus
    et al.
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
    Kock, Peder
    Lunds universitet.
    Pettersson, Håkan BL
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Centrum för kirurgi, ortopedi och cancervård, Radiofysikavdelningen US.
    RadiaCopter – UAS Gamma spectrometry for detection and identification of radioactive sources2011Ingår i: XVI Conference of the NSFS, Reykjavik Iceland, 22-25 August 2011: Current Challenges in Radiation Protection Conference Proceedings, 2011Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    With an unmanned helicopter (UAS), known as drones, equipped with a gamma spectrometer, one can achieve both a high spatial resolution and good range, and be able to approach a radioactive source closely. Linköping University, Sweden, is proposing a microdrone system that will fill a gap between man-portable measurement systems and full-sized airborne systems, complementing the car-driven measurement systems. The system may play a unique role in many of our contingency scenarios in terms of accessibility, versatility, efficiency, and is advantageous from the viewpoint of radiation protection as it can be controlled at a safe distance.

  • 102.
    Gårdestig, Magnus
    et al.
    Östergötlands Läns Landsting, Centrum för kirurgi, ortopedi och cancervård, Radiofysikavdelningen US. Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
    Pettersson, Håkan BL
    Östergötlands Läns Landsting, Centrum för kirurgi, ortopedi och cancervård, Radiofysikavdelningen US. Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
    Approved Personal Dosimetry for Medical Personnel using Direct Ion Storage Dosimeters2009Ingår i: IFMBE Proceedings vol. 25/III / [ed] Dössel, Schlegel, Heidelberg: Springer , 2009, s. 352-354Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    Dosimeters based on the Direct Ion Storage technology is used as the first approved electronic personal dosimeter in Sweden at the County Councils in Östergötland and Kalmar. TL dosimeters are replaced by DIS-1 dosimeters for all category A personnel at six hospitals with totally 300 dosimeter holders. The advantages are longer issue periods and instant read outs, appreciated by both the service and the holders

  • 103.
    Gårdestig, Magnus
    et al.
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
    Pettersson, Håkan BL
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Centrum för kirurgi, ortopedi och cancervård, Radiofysikavdelningen US.
    RadiaCopter - UAS Gamma spectrometry for detection and identification of radioactive sources2012Ingår i: IRPA13 the 13th International Congress of the International Radiation Protection Association, 2012, s. P09-22Konferensbidrag (Övrigt vetenskapligt)
  • 104.
    Gårdestig, Magnus
    et al.
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
    Örtenberg, Alexander
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
    Pettersson, Håkan BL
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Centrum för kirurgi, ortopedi och cancervård, Radiofysikavdelningen US.
    RadiaDroid – Simulated radiation detection in smartphones2011Ingår i: XVI Conference of the NSFS, Reykjavik Iceland, 22-25 August 2011: Current Challenges in Radiation Protection Conference Proceedings, 2011Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    RadiaDroid is an Android application that simulates the portable radiation detector Intensimeter 28 civ. and uses virtual radioactive sources, defined by GPS coordinates, radionuclide and activity. The trainees load a scenario and search the exercise area for radioactivity. The locations of sources and safety perimeters are reported. Creation of scenarios is possible in the application, but is facilitated in a PC tool that also presents the reports and the dose to the trainee.

  • 105. Hammersberg, P.
    et al.
    Stenström, Mats
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
    Maximising the signal-to-noise ratio in computerised tomography data using robust design1996Ingår i: Insight (Northampton), ISSN 1354-2575, E-ISSN 1754-4904, Vol. 38, nr 2, s. 112-117Artikel i tidskrift (Refereegranskat)
    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.

  • 106. Hammersberg, P.
    et al.
    Stenström, Mats
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
    Sandborg, Michael
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
    Matscheko, G.
    Alm Carlsson, Gudrun
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
    A theoretical model for determination of the optimal irradiation conditions for computerised tomography1995Ingår i: Insight (Northampton), ISSN 1354-2575, E-ISSN 1754-4904, Vol. 37, nr 12, s. 978-985Artikel i tidskrift (Refereegranskat)
    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.

  • 107. Hansson, T
    et al.
    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. Östergötlands Läns Landsting, Centrum för kirurgi, ortopedi och cancervård, Radiofysikavdelningen US. Östergötlands Läns Landsting, Diagnostikcentrum, Röntgenkliniken i Linköping. Linköpings universitet, Hälsouniversitetet.
    Björkman, A
    Nylander, L
    Nyman, T
    Rosén, B
    Lundborg, G
    Activation of the primary somatosensory cortex during stereoscopic observation of tactile stimulation of the hand2005Konferensbidrag (Övrigt vetenskapligt)
  • 108.
    Hansson, Thomas
    et al.
    Linköpings universitet, Institutionen för klinisk och experimentell medicin, Hand och plastikkirurgi. Linköpings universitet, Hälsouniversitetet.
    Nyman, Torbjörn
    Östergötlands Läns Landsting, Rekonstruktionscentrum, Hand- och plastikkirurgiska kliniken US.
    Björkman, Anders
    Malmö University Hospital.
    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.
    Nylander, Lotta
    Östergötlands Läns Landsting, Rekonstruktionscentrum, Hand- och plastikkirurgiska kliniken US.
    Rosén, Birgitta
    Malmö University Hospital.
    Lundborg, Göran
    Malmö University Hospital.
    Sights of touching activates the somatosensory cortex in humans.2009Ingår i: Scandinavian journal of plastic and reconstructive surgery and hand surgery / Nordisk plastikkirurgisk forening [and] Nordisk klubb for handkirurgi, ISSN 1651-2073, Vol. 43, nr 5, s. 267-269Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We report our observations of cross-modal interactions between sight and touch using functional magnetic resonance imaging (fMRI). Experiments were devised to show that sight and touch are linked in a cross-modal arrangement, and two separate experiments were done in an MRI scanner. In the first, the subject's right hand was stimulated with a brush; in the second, a video sequence was presented to the subject inside the scanner through video goggles in visual three-dimensional stereo, showing one brushstroke every second on a hand in the same manner as the subject had just previously experienced. The result was that both the primary and the secondary somatosensory cortexes were activated in the participants when the hands were touched, and when the subjects saw only a hand being touched in the same manner. The results indicated cross-modal links between sight and touch of the hand in humans.

  • 109.
    Hedlund, Anna
    et al.
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiologi. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Hälsouniversitetet.
    Ahrén, Maria
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Molekylär ytfysik och nanovetenskap. Linköpings universitet, Tekniska fakulteten.
    Gustafsson, Håkan
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV.
    Abrikossova, Natalia
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Molekylär ytfysik och nanovetenskap. Linköpings universitet, Tekniska fakulteten.
    Warntjes, Marcel
    Linköpings universitet, Institutionen för medicin och hälsa, Klinisk fysiologi. Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV.
    Jönsson, Jan-Ivar
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för klinisk och experimentell medicin, Medicinsk och fysiologisk kemi.
    Uvdal, Kajsa
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Molekylär ytfysik och nanovetenskap. Linköpings universitet, Tekniska fakulteten.
    Engström, Maria
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiologi. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Hälsouniversitetet.
    Gd2O3 nanoparticles in hematopoietic cells for MRI contrast enhancement2011Ingår i: International journal of nano medicine, ISSN 1178-2013, Vol. 6, s. 3233-3240Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    As the utility of magnetic resonance imaging (MRI) broadens, the importance of having specific and efficient contrast agents increases and in recent time there has been a huge development in the fields of molecular imaging and intracellular markers. Previous studies have shown that gadolinium oxide (Gd2O3) nanoparticles generate higher relaxivity than currently available Gd chelates: In addition, the Gd2O3 nanoparticles have promising properties for MRI cell tracking. The aim of the present work was to study cell labeling with Gd2O3 nanoparticles in hematopoietic cells and to improve techniques for monitoring hematopoietic stem cell migration by MRI. Particle uptake was studied in two cell lines: the hematopoietic progenitor cell line Ba/F3 and the monocytic cell line THP-1. Cells were incubated with Gd2O3 nanoparticles and it was investigated whether the transfection agent protamine sulfate increased the particle uptake. Treated cells were examined by electron microscopy and MRI, and analyzed for particle content by inductively coupled plasma sector field mass spectrometry. Results showed that particles were intracellular, however, sparsely in Ba/F3. The relaxation times were shortened with increasing particle concentration. Relaxivities, r1 and r2 at 1.5 T and 21°C, for Gd2O3 nanoparticles in different cell samples were 3.6–5.3 s-1 mM-1 and 9.6–17.2 s-1 mM-1, respectively. Protamine sulfate treatment increased the uptake in both Ba/F3 cells and THP-1 cells. However, the increased uptake did not increase the relaxation rate for THP-1 as for Ba/F3, probably due to aggregation and/or saturation effects. Viability of treated cells was not significantly decreased and thus, it was concluded that the use of Gd2O3 nanoparticles is suitable for this type of cell labeling by means of detecting and monitoring hematopoietic cells. In conclusion, Gd2O3 nanoparticles are a promising material to achieve positive intracellular MRI contrast; however, further particle development needs to be performed.

  • 110.
    Helmrot, Ebba
    et al.
    Linköpings universitet, Institutionen för medicin och vård, Radiofysik.
    Alm Carlsson, Gudrun
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Measurement of radiation dose in dental radiology.2005Ingår i: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 114, s. 168-171Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Patient dose audit is an important tool for quality control and it is important to have a well-defined and easy to use method for dose measurements. In dental radiology, the most commonly used dose parameters for the setting of diagnostic reference levels (DRLs) are the entrance surface air kerma (ESAK) for intraoral examinations and dose width product (DWP) for panoramic examinations. DWP is the air kerma at the front side of the secondary collimator integrated over the collimator width and an exposure cycle. ESAK or DWP is usually measured in the absence of the patient but with the same settings of tube voltage (kV), tube current (mA) and exposure time as with the patient present. Neither of these methods is easy to use, and, in addition, DWP is not a risk related quantity. A better method of monitoring patient dose would be to use a dose area product (DAP) meter for all types of dental examinations. In this study, measurements with a DAP meter are reported for intraoral and panoramic examinations. The DWP is also measured with a pencil ionisation chamber and the product of DWP and the height that it is feasible to measure DAP using a DAP meter for both intraoral and panoramic examinations. The DAP is therefore recommended for the setting of DRLs. H (DWP H) of the secondary collimator (measured using film) was compared to DAP. The results show that it is feasible to measure DAP using a DAP meter for both intraoral and panoramic examinations. The DAP is therefore recommended for the setting of DRLs.

  • 111. Helmrot, Ebba
    et al.
    Alm Carlsson, Gudrun
    Linköpings universitet, Institutionen för medicin och vård, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
    Eckerdal, Olof
    Sandborg, Michael
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik.
    Use of an ivory wedge as a test phantom in analysing the influence of scattered radiation and tube potential on radiolographic contrast in intraoral dental radiography1993Ingår i: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 49, nr 1, s. 125-127Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Contrast, noise and spatial resolution are fundamental physical concepts used to describe image quality. Contrast is one of the most important parameters in conventional film radiography. To facilitate the analysis of the radiographic contrast over a wide range of optical densities, an ivory wedge representative of objects with marked tissue discontinuities has been constructed. It can be used either separately or included within a PMMA phantom representing the middle face to simulate realistic scatter conditions. It is thus possible to investigate how radiographic contrast may be influenced by kV setting, beam filtration, type of generator (constant potential or single pulse) and type of film. The phantom has been used in optimising image quality relative to radiation risk, with the radiographic contrast being determined both theoretically and experimentally in terms of type of film (D and E speed), radiation and object contrast. The importance of controlling physical parameters when investigating image quality and how to achieve this using a well defined phantom is clearly demonstrated.

  • 112.
    Helmrot, Ebba
    et al.
    Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Alm Carlsson, Gudrun
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Hälsouniversitetet.
    Sandborg, Michael
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen. Linköpings universitet, Hälsouniversitetet.
    Influence of scattered radiation and tube potential on radiographic contrast: comparison of two different dental X-ray films1991Ingår i: Dento-Maxillo-Facial Radiology, ISSN 0250-832X, E-ISSN 1476-542X, Vol. 20, nr 3, s. 135-146Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The fundamental concept in image quality of contrast has been analysed in terms of its elements; film, radiation and object contrast, and the theoretical formula to describe their interrelationship have been evaluated. Experiments were designed to investigate the dependence of radiographic contrast on the kV, the type of generator and dental film used (D and E speed). An ivory wedge was used as the object, both alone and within a polymethyl methacrylate phantom as scattering medium. Precise definition and control of the X-ray generators were achieved by means of measurements of the primary X-ray spectra using a Compton spectrometer. D speed was found to have higher film contrast than E speed when compared at the same optical density, due to its lower base and fog and lower level of saturation in these experiments. On the other hand, E speed was found to have wider latitude. The experimental object was reproduced with the highest radiographic contrast using D-speed film and, with a given type of generator, this increased when the kV was decreased. While no difference in scatter/primary ratios was observed using the two different films, a weak dependence on kV in the range from 36 to 77 kV was found and confirmed by Monte Carlo calculations. The results indicate that the D and E speed films used had equal energy absorption properties; the difference in radiographic performance is due to their different film characteristics. The importance of controlling the physical parameters (photon energy spectrum, base and fog and optical density level) when comparing image qualities is clearly demonstrated.

  • 113.
    Helmrot, Ebba
    et al.
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Centrum för kirurgi, ortopedi och cancervård, Radiofysikavdelningen US.
    Pettersson, Håkan
    Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen. Linköpings universitet, Institutionen för medicin och vård, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
    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.
    Nilsson Althen, Jonas
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Centrum för kirurgi, ortopedi och cancervård, Radiofysikavdelningen US.
    Estimation of the dose to the unborn child at diagnostic X-ray examinations based on data registrerad in RIS/PACS2007Ingår i: European Radiology, ISSN 0938-7994, E-ISSN 1432-1084, Vol. 17, nr 1, s. 205-209Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The aim of this work was to determine mean absorbed doses to the unborn child in common conventional X-ray and computed tomography (CT) examinations and to find an approach for estimating foetal dose based on data registered in the Radiological Information System/Picture Archive and Communication System (RIS/PACS). The kerma-area product (KAP) and CT dose index (CTDIvol) in common examinations were registered using a human-shaped female dosimetry phantom. Foetal doses, Df, were measured using thermoluminescent dosimeters placed inside the phantom and compared with calculated values. Measured foetal doses were given in relation to the KAP and the CTDIvol values, respectively. Conversion factor Df/KAP varies between 0.01 and 3.8 mGy/Gycm2, depending on primary beam position, foetus age and beam quality (tube voltage and filtration). Conversion factors Df/CTDIvol are in the range 0.02 – 1.2 mGy/mGy, in which the foetus is outside or within the primary beam. We conclude that dose conversion factors based on KAP or CTDIvol values automatically generated by the RIS/PACS system can be used for rapid estimations of foetal dose for common examination techniques.

  • 114.
    Holm, Åsa
    et al.
    Linköpings universitet, Matematiska institutionen. Linköpings universitet, Tekniska högskolan.
    Larsson, Torbjörn
    Linköpings universitet, Matematiska institutionen, Optimeringslära. Linköpings universitet, Tekniska högskolan.
    Carlsson Tedgren, Åsa
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
    Impact of Using Linear Optimization Models in Dose Planning for HDR Brachytherapy2012Ingår i: Medical physics (Lancaster), ISSN 0094-2405, Vol. 39, nr 2, s. 1021-1028Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Purpose: Dose plans generated with optimization models hitherto used in HDR brachytherapy have shown a tendency to yield longer dwell times than manually optimized plans. Concern has been raised for the corresponding undesired hot spots and various methods to mitigate these have been developed. The hypotheses of this work are a) that one cause for the long dwell times is the use of objective functions comprising simple linear penalties and b) that alternative penalties, being piecewise linear, would lead to reduced length of individual dwell times.

    Methods: The characteristics of the linear penalties and the piecewise linear penalties are analysed mathematically. Experimental comparisons between the two types of penalties are carried out retrospectively for a set of prostate cancer patients.

    Results: While most dose-volume parameters do not differ significantly between the two types of penalties significant changes can be seen in the dwell times. On the average, total dwell times were reduced by 4.2%, with a reduction of maximum dwell times by 30%, using the alternative penalties.

    Conclusion: The use of linear penalties in optimization models for HDR brachytherapy is one cause for undesired longer dwell times appearing in mathematically optimized plans. By introducing alternative penalties significant reduction in dwell times can be achieved for HDR brachytherapy dose plans. Although various constraints as to reduce the long dwell times have been developed our finding is of fundamental interest in showing the shape of the objective function to be one reason for their appearance.

  • 115.
    Holm, Åsa
    et al.
    Linköpings universitet, Matematiska institutionen. Linköpings universitet, Tekniska högskolan.
    Larsson, Torbjörn
    Linköpings universitet, Matematiska institutionen, Optimeringslära. Linköpings universitet, Tekniska högskolan.
    Carlsson Tedgren, Åsa
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Centrum för kirurgi, ortopedi och cancervård, Radiofysikavdelningen US.
    On the Correlation Between DVH Parameters and Linear Penalties in Optimization of HDR Prostate Brachytherapy Dose PlansManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    When optimizing dwell times for HDR brachytherapy it is common to use a model comprising an objective of linear penalties. However whether a planis considered good or not depends on other measures such as DVH-based parameters. We show through experiments that the correlation between the value of the objective function and the values of DVH-based parameters, such as D90, is weak in some cases. It seems that the objective function can only classify solutions into better or worse, however it can not distinguish the best with respect to DVH-based parameters.

  • 116.
    Israelsson, Axel
    et al.
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
    Gustafsson, Håkan
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
    Lund, Eva
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
    Dose response of xylitol and sorbitol for EPR retrospective dosimetry with applications to chewing gum2013Ingår i: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 154, nr 2, s. 133-141Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The purpose of this investigation was to study the radiation-induced electron paramagnetic resonance signal in sweeteners xylitol and sorbitol for use in retrospective dosimetry. For both sweeteners and chewing gum, the signal changed at an interval of 1–84 d after irradiation with minimal changes after 4–8 d. A dependence on storage conditions was noticed and the exposure of the samples to light and humidity was therefore minimised. Both the xylitol and sorbitol signals showed linearity with dose in the measured dose interval, 0–20 Gy. The dose-response measurements for the chewing gum resulted in a decision threshold of 0.38 Gy and a detection limit of 0.78 Gy. A blind test illustrated the possibility of using chewing gums as a retrospective dosemeter with an uncertainty in the dose determination of 0.17 Gy (1 SD).

  • 117.
    Janerot-Sjöberg, Birgitta
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan. Östergötlands Läns Landsting, Hjärt- och Medicincentrum, Fysiologiska kliniken US.
    Ekberg, Stefan
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Centrum för kirurgi, ortopedi och cancervård, Radiofysikavdelningen US.
    Areskog, M.
    Department of Clinical Physiology, Kalmar Regional Hospital.
    Nylander, Eva
    Linköpings universitet, Institutionen för medicin och hälsa, Klinisk fysiologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Hjärt- och Medicincentrum, Fysiologiska kliniken US.
    Swahn, Eva
    Linköpings universitet, Institutionen för medicin och hälsa, Kardiologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Hjärt- och Medicincentrum, Kardiologiska kliniken US.
    Quantitative digital evaluation of myocardial exercise thallium-201 single-photon emission tomography in post-menopausal women1998Ingår i: Clinical Physiology, ISSN 0144-5979, E-ISSN 1365-2281, Vol. 18, nr 3, s. 169-177Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Quantitative computerized analysis of data from myocardial thallium-201 (201Tl) single-photon emission tomography (SPET) may improve the diagnostic accuracy of coronary heart disease. The reference ranges for post-menopausal women are, however, limited and obtained mainly from patients. To compare reference values from healthy post-menopausal women and to improve the quantitative analysis, 20 women (10 patients with coronary heart disease and previous infarction and 10 age-matched healthy volunteers) were examined immediately post exercise and after a delay. A nine-segment 'bull's-eye' model was used for analysis. At visual evaluation, reproducibility was high (93%), no false-positive results were obtained and in 70% of the patients the SPET was interpreted as abnormal. Using reported reference values for quantitative analysis, all the healthy women had an abnormal result. New reference values based on three different methods of 'normalization' were calculated: the relative activity of segment 3 set to 100%, the segment with the highest activity set to 100% and a least-squares method. They all differed significantly from those that had previously been reported. The frequencies of agreement between visual and quantitative analysis were 84-92% and were highest when segment 3 was used as a reference, but in this case only 40% of the patients with coronary heart disease had an abnormal SPET. Using the least-squares method for handling digital information, the SD of the normal values decreased and 90% of the patients with coronary heart disease were accurately diagnosed. These results provide quantitative digital reference values for healthy post-menopausal women. They verify that quantitative analysis is in diagnostic agreement with visual evaluation, stress the need for local verification of reference ranges and suggest a least-square normalization method for the analysis.

  • 118. Jangland, L
    et al.
    Sanner, E
    Persliden, Jan
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Dose reduction in computed tomography by individualized scan protocols2004Ingår i: Acta Radiologica, ISSN 0284-1851, E-ISSN 1600-0455, Vol. 45, nr 3, s. 301-307Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Purpose: To find a method of adjusting the mAs-value in relation to the size of the patient undergoing computed tomography (CT) examination as a means of minimizing the radiation dose to the patient. Material and Methods: A correction factor to be applied on the tube charge for each patient was calculated using two mathematical methods. This approach was tested on 4 Perspex phantoms of different sizes and geometries. Noise was measured in the images with and without use of the correction factors. Retrospectively, correction factors were calculated for 12 CT examinations of the abdomen and the dose reduction was estimated for these patient studies. Results: The variations in noise measured in the images of the different phantoms were dramatically reduced by both methods. The retrospectively performed patient study showed that the largest correction factor was 7 times greater than the smallest, which means that a dose reduction factor of 7 is possible in the extreme case. Conclusion: Our proposed methods of adjusting the applied tube charge (mAs-value) in relation to the size of the patient can be used on the vast majority of CT systems. The potential for dose reduction is great, especially for small patients.

  • 119.
    Jansson, Margareta
    et al.
    Department of Radiology, Örebro University Hospital, 701 85 Örebro, Sweden.
    Geijer, Håkan
    Department of Radiology, Örebro University Hospital, 701 85 Örebro, Sweden.
    Persliden, Jan
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Andersson, Torbjörn
    Department of Radiology, Örebro University Hospital, 701 85 Örebro, Sweden.
    Reducing dose in urography while maintaining image quality - A comparison of storage phosphor plates and a flat-panel detector2006Ingår i: European Radiology, ISSN 0938-7994, E-ISSN 1432-1084, Vol. 16, nr 1, s. 221-226Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The introduction of new flat-panel detector technology often forces us to accept too high dose levels as proposed by the manufacturers. We need a tool to compare the image quality of a new system with the accepted standard. The aim of this study was to obtain a comparable image quality for two systems - storage phosphor plates and a flat-panel system using intravenous urography (IVU) as a clinical model. The image quality figure was calculated using a contrast-detail phantom (CDRAD) for the two evaluated systems. This allowed us to set a dose for the flat-panel system that gave equivalent image quality to the storage phosphor plates. This reduced detector dose was used in an evaluation of clinical images to find out if the dose reduction from the phantom study indeed resulted in images of equal clinical image quality. The image quality was assessed using image criteria of the European guidelines for IVU with visual grading analysis. Equivalent image quality in image pairs was achieved at 30% of the dose. The CDRAD contrast-detail phantom makes it possible to find dose levels that give equal image quality using different imaging systems. © Springer-Verlag 2005.

  • 120. Jaworski, J
    et al.
    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. Östergötlands Läns Landsting, Centrum för kirurgi, ortopedi och cancervård, Radiofysikavdelningen US. Östergötlands Läns Landsting, Diagnostikcentrum, Röntgenkliniken i Linköping. Linköpings universitet, Hälsouniversitetet.
    Gladigau, D
    Gustafsson, M C
    Landtblom, Anne-Marie
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för klinisk och experimentell medicin, Psykiatri. Östergötlands Läns Landsting, Sinnescentrum, Neurokirurgiska kliniken US. Linköpings universitet, Hälsouniversitetet.
    Follow-up of absolute metabolite concentrations using MR spectroscopy in MS patients with interferon-b treatment2008Konferensbidrag (Övrigt vetenskapligt)
  • 121.
    Jaworski, J
    et al.
    Linköpings universitet, Institutionen för medicin och hälsa. Linköpings universitet, Hälsouniversitetet.
    Dahlqvist Leinhard, Olof
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
    Tisell, Anders
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    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.
    Landtblom, Anne-Marie
    Linköpings universitet, Institutionen för klinisk och experimentell medicin, Neurologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Närsjukvården i västra Östergötland, Medicinska specialistkliniken .
    Treatment with glatiramer acetate (Copaxone (R)) prevents neurodegeneration in patients with multiple sclerosis2009Ingår i: in MULTIPLE SCLEROSIS, vol 15, issue 9, 2009, Vol. 15, nr 9, s. S140-S141Konferensbidrag (Refereegranskat)
    Abstract [en]

    n/a

  • 122.
    Kalra, Mannudeep K.
    et al.
    Massachusetts General Hospital, Boston, USA .
    Persson, Anders
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Diagnostikcentrum, Röntgenkliniken i Linköping.
    Quick, Petter
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiologi. Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Östergötlands Läns Landsting, Diagnostikcentrum, Röntgenkliniken i Linköping.
    Digumarthy, Subba Rao
    Massachusetts General Hospital, Boston, USA .
    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, Centrum för kirurgi, ortopedi och cancervård, Radiofysikavdelningen US.
    Singh, Sarabjeet
    Massachusetts General Hospital, Boston, USA .
    Can image space iterative reconstruction technique allow 60% dose reduction for thoracic CT? Results for a randomised prospective pilot study2010Ingår i: SSQ03-06, 2010Konferensbidrag (Övrigt vetenskapligt)
  • 123.
    Kalra, Mannudeep K.
    et al.
    Massachusetts General Hospital, Boston, USA .
    Persson, Anders
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Diagnostikcentrum, Röntgenkliniken i Linköping.
    Quick, Petter
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiologi. Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Östergötlands Läns Landsting, Diagnostikcentrum, Röntgenkliniken i Linköping.
    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, Centrum för kirurgi, ortopedi och cancervård, Radiofysikavdelningen US.
    Combining high pitch, low kV and 4D automatic exposure controll technique for reducing CT radiation dose for mapping of pulmonary venous anatomy2010Ingår i: SSJ05-05, 2010Konferensbidrag (Övrigt vetenskapligt)
  • 124.
    Kalra, Mannudeep
    et al.
    Massachusetts General Hospital, Boston, USA.
    Persson, Anders
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Diagnostikcentrum, Röntgenkliniken i Linköping.
    Quick, Petter
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiologi. Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Östergötlands Läns Landsting, Diagnostikcentrum, Röntgenkliniken i Linköping.
    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, Centrum för kirurgi, ortopedi och cancervård, Radiofysikavdelningen US.
    Combining low kVp, lowest tube current, high pitch and fast table speed for minimizing radiation dose for whole body CT imaging of children with scoliosis2010Ingår i: SSK14-08, 2010Konferensbidrag (Övrigt vetenskapligt)
  • 125.
    Kalra, Mannudeep
    et al.
    Massachusetts General Hospital, Boston, MA, USA .
    Quick, Petter
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Diagnostikcentrum, Röntgenkliniken i Linköping.
    Singh, Sarabjeet
    Massachusetts General Hospital, Boston, MA, USA .
    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, Centrum för kirurgi, ortopedi och cancervård, Radiofysikavdelningen US.
    Persson, Anders
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Diagnostikcentrum, Röntgenkliniken i Linköping.
    Whole spine CT for evaluation of scoliosis in children: feasibility of sub-milliSievert scanning protocol2013Ingår i: Acta Radiologica, ISSN 0284-1851, E-ISSN 1600-0455, Vol. 54, nr 2, s. 226-230Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Background Optimization of CT radiation dose is important for children due to their higher risk of radiation-induced adverse effects. Anatomical structures with high inherent contrast, such as bones can be imaged at very low radiation doses by optimizing scan parameters.                    

    Purpose To assess feasibility of sub-milliSievert whole spine CT scanning protocol for evaluation of scoliosis in children.                    

    Material and Methods With approval of the ethical board, we performed whole spine CT for evaluation of scoliosis in 22 children (age range, 3–18 years; mean age, 13 years; 13 girls, 9 boys) on a 128-slice dual source multidetector-row CT scanner. Lowest possible quality reference mAs value (image quality factor for xy-z automatic exposure control or xyz-AEC, CARE Dose 4D) was selected on a per patient basis. Remaining parameters were held constant at 3.0:1 pitch, 128 × 0.6 mm detector collimation, 115.2 mm table feed per gantry rotation, 100 kVp, and 1 and 3 mm reconstructed sections. Average mAs, projected estimated dose savings with AEC, computed tomography dose index volume (CTDI vol), and dose length product (DLP) were recorded. Artifacts were graded on a four-point scale (1, no artifacts; 4, severe artifacts). Ability to identify vertebral and pedicular contours, and measure pedicular width and degree of vertebral rotation was graded on a three-point scale (1, unacceptable; 3, excellent).       

    Results All CT examinations were deemed as reliable for identifying vertebral and pedicular contours as well as for measuring pedicular width (5.9 ± 1.6 mm) and degree of vertebral rotation (28.7 ± 23.4°). Mean objective image noise and signal to noise ratio (SNR) were 57.5 ± 21.5 and 4.7 ± 2.3, respectively. With a mean quality reference mAs of 13, the scanner employed an average actual effective mAs of 10 ± 3.8 (range, 6–18 mAs) with an estimated radiation dose saving of 43.5 ± 16.3% with xyz-AEC compared with fixed mAs. The mean CTDI, DLP, and estimated effective doses were 0.4 ± 0.1 mGy (0.2–0.7 mGy), 21 ± 10 mGy.cm (8–41 mGy.cm), and 0.3 ± 0.1 mSv (0.12–0.64 mSv), respectively.                    

    Conclusion Radiation dose for whole spine CT for evaluation of scoliosis in children can be minimized to less than one-third of a milliSievert while maintaining diagnostic image quality.

  • 126.
    Karakirova, Yordanka
    et al.
    Bulgarian Academy of Sciences.
    Lund, Eva
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
    Yordanov , Nicola D
    Bulgarian Academy of Sciences.
    EPR and UV investigation of sucrose irradiated with nitrogen ions and gamma-rays2008Ingår i: Radiation Measurements, ISSN 1350-4487, E-ISSN 1879-0925, Vol. 43, nr 8, s. 1337-1342Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Sucrose irradiated with N-ions and gamma-rays is investigated by EPR and UV spectroscopy. Irradiation doses are in the range of 20-380 Gy and linear energy transfer (LET) for N-ions of 90, 125 and 160 keV mu m(-1). All EPR spectra recorded in irradiated solid samples are identical, suggesting that generated free radicals are not sensitive to the radiation quality. The EPR response of free radicals linearly depends on the absorbed dose but when generated by N-ions it is always lower than that obtained by irradiation with the same absorbed dose from gamma-rays. Water solutions of irradiated sucrose exhibit UV absorption at 267 nm due to the product of free radicals recombination, which spectrum remains independent on the radiation quality. The intensity of this band however depends on the absorbed dose and for equal doses it is higher for samples irradiated with N-ions than with gamma-rays. For different high LET-radiations with N-ions and low-LET radiation from gamma rays is found an excellent linearity between the EPR signal intensity and the UV absorbance of the obtained water solution. The relation between EPR and UV response of N-ions irradiated samples is reciprocal as well as between them and gamma-irradiated samples suggesting different impact of the high-energy photons and heavy particles on the solid state. For low LET photon radiation with moderate dose rate the probability for a successful hitting of two neighboring molecules is low. Therefore, only a small part of low LET radiation-induced free radicals may be expected to recombine giving an UV detectable product. In opposite, because of the dense ionizations and heaviness of N-ions almost all molecules in the core of the track are ionized yielding mainly products of the recombined free radicals. In the outer part of the track delta particles, which are more like low LET radiation electrons, stands for ionizations and produces a small number of free radicals situated far from each other. Therefore, we can expect higher EPR response of sugar irradiated with a certain dose of gamma-rays than of heavy particles. Just the opposite behavior should be expected for the UV absorption, which should be higher in the irradiation with heavy particles than with gamma-rays. The reported observations suggest that a sucrose/UV/EPR dosimetric system seems to be very promising for dose determinations from both gamma and heavy particle radiation and indicate a method for simultaneous determination of absorbed dose and LET. It also seems to be a new way for calibration of EPR dosimeters irradiated with N-ions via UV spectrometry.

  • 127.
    Karlsson, Anette
    et al.
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för medicinsk teknik, Medicinsk informatik. Linköpings universitet, Tekniska högskolan.
    Dahlqvist Leinhard, Olof
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
    Romu, Thobias
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för medicinsk teknik, Medicinsk informatik. Linköpings universitet, Tekniska högskolan.
    Borga, Magnus
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för medicinsk teknik, Medicinsk informatik. Linköpings universitet, Tekniska högskolan.
    Automated Whole Body Muscle Segmentation & Classification2012Ingår i: ISMRM workshop on Fat-­‐Water Separation: Insights, Applications & Progress in MRI, 2012Konferensbidrag (Övrigt vetenskapligt)
  • 128.
    Karlsson, Anette
    et al.
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för medicinsk teknik, Medicinsk informatik. Linköpings universitet, Tekniska högskolan.
    Dahlqvist Leinhard, Olof
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
    Vallin, Anna
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV.
    Romu, Thobias
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för medicinsk teknik, Medicinsk informatik. Linköpings universitet, Tekniska högskolan.
    Borga, Magnus
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för medicinsk teknik, Medicinsk informatik. Linköpings universitet, Tekniska högskolan.
    Automated Whole Body Muscle Quantification Based on a 10 min MR-Exam2012Ingår i: Proceedings of the annual meeting of the International Society for Magnetic Resonance in Medicine (ISMRM 2012), 2012Konferensbidrag (Övrigt vetenskapligt)
  • 129.
    Karlsson, Anette
    et al.
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    Magnusson, Maria
    Linköpings universitet, Institutionen för systemteknik, Datorseende. Linköpings universitet, Tekniska högskolan.
    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, Centrum för kirurgi, ortopedi och cancervård, Radiofysikavdelningen US. Östergötlands Läns Landsting, Diagnostikcentrum, Röntgenkliniken i Linköping.
    Successful Motion Correction in Reconstruction of Radial MRI2011Konferensbidrag (Refereegranskat)
  • 130.
    Karlsson, Henrik
    et al.
    Östergötlands Läns Landsting, Centrum för kirurgi, ortopedi och cancervård, Radiofysikavdelningen US.
    Gustafsson, Agnetha
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Centrum för kirurgi, ortopedi och cancervård, Radiofysikavdelningen US.
    Fingerdosmätningar vid olika moment vid hantering av 18F-FDG2008Konferensbidrag (Övrigt vetenskapligt)
  • 131.
    Karlsson, Henrik
    et al.
    Östergötlands Läns Landsting, Centrum för kirurgi, ortopedi och cancervård, Radiofysikavdelningen US.
    Lindblom, Gunnar
    Östergötlands Läns Landsting, Diagnostikcentrum, Röntgenkliniken i Linköping.
    Brundin, Helene
    Östergötlands Läns Landsting, Hjärt- och Medicincentrum, Fysiologiska kliniken US.
    Gustafsson, Agnetha
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Centrum för kirurgi, ortopedi och cancervård, Radiofysikavdelningen US.
    Optimering av dosering vid skelettscintigrafi – en VGC-studie2008Konferensbidrag (Övrigt vetenskapligt)
  • 132.
    Karlsson, Mattias P
    et al.
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
    Halse, Tore
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
    Carlsson, Marie
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Centrum för kirurgi, ortopedi och cancervård, Radiofysikavdelningen US.
    Gårdestig, Magnus
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
    Stark, Karolina
    Stockholms universitet, Systems Ecology.
    Pettersson, Håkan BL
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Centrum för kirurgi, ortopedi och cancervård, Radiofysikavdelningen US.
    External radiation doses to biota: Monte Carlo dose model calculations2011Ingår i: XVI Conference of the NSFS, Reykjavik Iceland, 22-25 August 2011: Current Challenges in Radiation Protection Conference Proceedings, 2011Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    Realistic and reliable dose models are required to estimate the radiological risks to non-human biota, in regions contaminated by radioactivity. To facilitate detailed dose calculations, a graphical user interface has been developed to the Monte Carlo N-Particle Transport code (MCNP): the TADPOLE editor (Terrestrial and Aquatic Dose assessment Program for Organisms in their Local Environment). The editor is intended for site and biota specific analyses of absorbed dose from external γ- and β- radiation.

    An experiment was performed in controlled, laboratory conditions as a first validation of the calculation models assigned by the editor. Measurements with TL-dosimeters yielded lower doses than was calculated by MCNP5 through the editor.

  • 133.
    Kechagias, Stergios
    et al.
    Linköpings universitet, Institutionen för medicin och hälsa, Internmedicin. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Medicincentrum, Endokrin- och magtarmmedicinska kliniken US.
    Ernersson, Åsa
    Linköpings universitet, Institutionen för medicin och hälsa, Omvårdnad. Linköpings universitet, Hälsouniversitetet.
    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, Internmedicin. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Lindström, Torbjörn
    Linköpings universitet, Institutionen för medicin och hälsa, Internmedicin. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Medicincentrum, Endokrin- och magtarmmedicinska kliniken US.
    Nyström, Fredrik
    Linköpings universitet, Institutionen för medicin och hälsa, Internmedicin. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Medicincentrum, Endokrin- och magtarmmedicinska kliniken US.
    Länne, Toste
    Linköpings universitet, Institutionen för medicin och hälsa, Avdelningen för kardiovaskulär medicin. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Hjärt- och Medicincentrum, Kardiologiska kliniken US.
    Fast-food-based hyper-alimentation can induce rapid and profound elevation of serum alanine aminotransferase in healthy subjects2008Ingår i: Gut, ISSN 0017-5749, E-ISSN 1468-3288, Vol. 57, nr 5, s. 649-654Artikel i tidskrift (Refereegranskat)
    Abstract [en]

     Objective: To study the effect of fast-food-based hyperalimentation on liver enzymes and hepatic triglyceride content (HTGC).

    Design: Prospective interventional study with parallel control group.

    Setting: University Hospital of Linko¨ping, Sweden.

    Participants: 12 healthy men and six healthy women with a mean (SD) age of 26 (6.6) years and a matched control group.

    Intervention: Subjects in the intervention group aimed for a body weight increase of 5–15% by eating at least two fast-food-based meals a day with the goal to double the regular caloric intake in combination with adoption of a sedentary lifestyle for 4 weeks.

    Main outcome measures: Weekly changes of serum aminotransferases and HTGC measured by proton nuclear magnetic resonance spectroscopy at baseline and after the intervention.

    Results: Subjects in the intervention group increased from 67.6 (9.1) kg to 74.0 (11) kg in weight (p,0.001). Serum ALT increased from 22.1 (11.4) U/l at study start to an individual mean maximum level of 97 (103) U/l (range 19.4–447 U/l). Eleven of the 18 subjectspersistently showed ALT above reference limits (women .19 U/l, men .30 U/l) during the intervention. Sugar (mono- and disaccharides) intake during week 3 correlated with the maximal ALT/baseline ALT ratio(r=0.62, p=0.006). HTGC increased from 1.1 (1.9)% to 2.8 (4.8)%, although this was not related to the increase in ALT levels. ALT levels were unchanged in controls.

    Conclusion: Hyper-alimentation per se can induce profound ALT elevations in less than 4 weeks. Our study clearly shows that in the evaluation of subjects with elevated ALT the medical history should include not only questions about alcohol intake but also explore whetherrecent excessive food intake has occurred.

  • 134.
    Kechagias, Stergios
    et al.
    Linköpings universitet, Institutionen för medicin och hälsa, Internmedicin. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Hjärt- och Medicincentrum, Endokrin- och magtarmmedicinska kliniken US.
    Zanjani, Sepehr
    Linköpings universitet, Institutionen för medicin och hälsa, Internmedicin. Linköpings universitet, Hälsouniversitetet.
    Gjellan, Solveig
    Linköpings universitet, Institutionen för medicin och hälsa, Internmedicin. Linköpings universitet, Hälsouniversitetet.
    Dahlqvist Leinhard, Olof
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV.
    Kihlberg, Johan
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiologi. Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Östergötlands Läns Landsting, Diagnostikcentrum, Röntgenkliniken i Linköping.
    Smedby, Örjan
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Diagnostikcentrum, Röntgenkliniken i Linköping.
    Johansson, Lars
    Uppsala University.
    Kullberg, Joel
    Uppsala University.
    Ahlstrom, Hakan
    Uppsala University.
    Lindström, Torbjörn
    Linköpings universitet, Institutionen för medicin och hälsa, Internmedicin. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Hjärt- och Medicincentrum, Endokrin- och magtarmmedicinska kliniken US.
    Nyström, Fredrik
    Linköpings universitet, Institutionen för medicin och hälsa, Internmedicin. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Hjärt- och Medicincentrum, Endokrin- och magtarmmedicinska kliniken US.
    Effects of moderate red wine consumption on liver fat and blood lipids: a prospective randomized study2011Ingår i: Annals of Medicine, ISSN 0785-3890, E-ISSN 1365-2060, Vol. 43, nr 7, s. 545-554Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Background : There have been no human prospective randomized studies of the amount of alcohol that can induce hepatic steatosis. less thanbrgreater than less thanbrgreater thanMethods : Thirty-two healthy women and twelve healthy men (34 +/- 9 years of age) were randomized to consume 150 ml of red wine/day for women (16 g ethanol/day) or double that amount for men (33 g ethanol/day), or to alcohol abstention for 90 days. Participants underwent proton-nuclear magnetic-resonance spectroscopy for measurement of hepatic triglyceride content (HTGC). Blood samples for assessment of cardiovascular risk were drawn before and after the intervention. less thanbrgreater than less thanbrgreater thanResults: After exclusion of three subjects with steatosis at baseline a trend towards increased HTGC was apparent for red wine (before median: 1.1%, range 0.2-3.9%, after median: 1.1%, range 0.5-5.2%, P = 0.059) a difference that was statistically significant compared with abstainers (p = 0.02). However, no subject developed hepatic steatosis. Low-density lipoprotein (LDL)-cholesterol was lowered by red wine (-0.3 mmol/l, SE-0.1, 95% CI-0.6 to -0.04). less thanbrgreater than less thanbrgreater thanConclusions: Moderate consumption of red wine during three months increased HTGC in subjects without steatosis at baseline. However, since not a single participant developed steatosis we suggest that the threshold of alcohol consumption to define nonalcoholic fatty liver disease should not be lower than the amount in our study.

  • 135.
    Kihlberg, Johan
    et al.
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Bildmedicinskt centrum, Röntgenkliniken i Linköping.
    Klintström, Eva
    Östergötlands Läns Landsting, Diagnostikcentrum, Röntgenkliniken i Linköping. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiologi. Linköpings universitet, Hälsouniversitetet.
    Dahlgren, A-C
    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. Östergötlands Läns Landsting, Centrum för kirurgi, ortopedi och cancervård, Radiofysikavdelningen US. Östergötlands Läns Landsting, Diagnostikcentrum, Röntgenkliniken i Linköping. Linköpings universitet, Hälsouniversitetet.
    Which Orthodontic Brackets Are Most Suitable for MRI?2010Konferensbidrag (Refereegranskat)
  • 136. Kim, CK
    et al.
    Kim, CS
    Chang, BU
    Choi, SW
    Chung, CS
    Hong, GH
    Hirose, K
    Pettersson, Håkan
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Pu-240/Pu-239 atom ratios in the bottom sediments of the NW Pacific Ocean2003Ingår i: Journal of Radioanalytical and Nuclear Chemistry, ISSN 0236-5731, E-ISSN 1588-2780, Vol. 258, nr 2, s. 265-268Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Pu239+240 concentrations and Pu-240/Pu-239 atom ratios in bottom sediments of the Yellow Sea, Korea Strait, East Sea (Sea of Japan), Sea of Okhotsk, and Northwest Pacific Ocean were determined. In coastal sediments near the Korean Peninsula, Pu239+240 concentrations varied from 0.02 to 1.72 Bq.kg(-1), and their Pu-240 /Pu-239 atom ratios from 0.15 to 0.24, with an average of 0.20+/-0.03. Pu-240/Pu-239 atom ratios of bottom sediments in the deep NW Pacific Ocean and its marginal seas(East,Okhotsk seas) were in the range of 0.15-0.23. A little elevated Pu-240/Pu-239 atom ratios in the bottom layer sediment may be due to Pu released into the environment during the pre-moratorium period, having high Pu-240 /Pu-239 atom ratios and low Pu-238/Pu239+240 activity ratios.

  • 137.
    Kvernby, Sofia
    et al.
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik.
    Olsson, Anna
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
    Gustafsson, Agnetha
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Centrum för kirurgi, ortopedi och cancervård, Radiofysikavdelningen US.
    Opimization of activity level in rCBF SPECT using observer study Visual Grading Regression2012Konferensbidrag (Övrigt vetenskapligt)
  • 138.
    Landtblom, Anne-Marie
    et al.
    Linköpings universitet, Institutionen för klinisk och experimentell medicin. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Närsjukvården i centrala Östergötland, Neurologiska kliniken.
    Jaworski, Jacek
    Östergötlands Läns Landsting, Närsjukvården i centrala Östergötland, Neurologiska kliniken.
    Dahlqvist Leinhard, Olof
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
    Gustafsson, Maria C
    Östergötlands Läns Landsting, Närsjukvården i centrala Östergötland, Neurologiska kliniken.
    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 metabolite concentrations in cerebral white matter of multiple sclerosis patients with beta interferon treatment2008Ingår i: MULTIPLE SCLEROSIS,ISSN 1352-4585: Volume 14, 2008, Vol. 14, s. S162-S162Konferensbidrag (Refereegranskat)
  • 139.
    Landtblom, Anne-Marie
    et al.
    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 .
    Lindehammar, Hans
    Linköpings universitet, Institutionen för klinisk och experimentell medicin, Klinisk neurofysiologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Sinnescentrum, Neurofysiologiska kliniken US.
    Karlsson, Henrik
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Centrum för kirurgi, ortopedi och cancervård, Radiofysikavdelningen US.
    Craig, A D (Bud)
    Barrow Neurol Institute.
    Insular cortex activation in a patient with "sensed presence"/ecstatic seizures2011Ingår i: EPILEPSY and BEHAVIOR, ISSN 1525-5050, Vol. 20, nr 4, s. 714-718Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Objective: Seizures with an aura of a "sensed presence," a religious emotion, or feelings of euphoria (ecstatic seizures) are characterized by heightened self-awareness. A previous case report on a patient with epilepsy and "sensed presence" as an aura described hypoperfusion in both temporal lobes and a local ictal increase in the left frontoparietal area. A reexamination of the data was suggested by a recent study of patients with ecstatic seizures, which proposed that hyperactivation of the left anterior insula might be a potential cause. Methods: We reanalyzed the laboratory data on the case with "sensed presence" aura using a fusion of SPECT and MR images of the brain, which had not previously been available, and a close examination of the subdural ictal EEG registrations. Results: Examination of the ictal EEG recordings from subdural strip electrodes implanted subtemporally and temporally on both sides showed that seizure activity occurred first at the most medial subtemporal electrode on the left side. From an anatomical point of view, this electrode position is close to the ventral aspect of the left anterior insula, and it is possible that the seizure activity was initiated there. Reexamination of the SPECT data after fusion with contemporary MR images clearly indicated that the region of strong hyperactivation overlies the left anterior insula. Hyperactive regions also appear on the midinsula bilaterally. Together with the neurophysiological ictal EEG, this evidence supports a reinterpretation that this aura of "sensed presence" can be attributed to hyperactivation of the left anterior insula. Conclusion: The present findings support the proposal that ecstatic seizures or "sensed presence" auras can originate from the left anterior insula, a region that has been suggested to engender self-awareness associated with positive feelings.

  • 140. Larsson, M. B. O.
    et al.
    Tillisch, K.
    Mayer, E. A.
    Jarcho, J.
    Lalbus, J.
    Naliboff, B.
    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, Centrum för kirurgi, ortopedi och cancervård, Radiofysikavdelningen US.
    Ström, Magnus
    Linköpings universitet, Institutionen för klinisk och experimentell medicin, Gastroenterologi och hepatologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Hjärt- och Medicincentrum, Endokrin- och magtarmmedicinska kliniken US.
    Walter, Susanna
    Linköpings universitet, Institutionen för klinisk och experimentell medicin, Gastroenterologi och hepatologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Hjärt- och Medicincentrum, Endokrin- och magtarmmedicinska kliniken US.
    Brain response during expectation and delivery of visceral stimulation differs between IBS patients and healthy controls: an fMRI study2010Konferensbidrag (Övrigt vetenskapligt)
  • 141.
    Larsson, Mats
    et al.
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för klinisk och experimentell medicin, Gastroenterologi och hepatologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Hjärt- och Medicincentrum, Endokrin- och magtarmmedicinska kliniken US.
    Tillisch, Kirsten
    UCLA, Los Angeles, USA.
    Craig, Bud
    Barrow Neurological Institute, Phoenix, Arizona.
    Engström, Maria
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiologi. Linköpings universitet, Hälsouniversitetet.
    Labus, Jennifer
    UCLA, Los Angeles, USA.
    Naliboff, Bruce
    UCLA, Los Angeles, USA.
    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, Centrum för kirurgi, ortopedi och cancervård, Radiofysikavdelningen US. Östergötlands Läns Landsting, Diagnostikcentrum, Röntgenkliniken i Linköping.
    Ström, Magnus
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för klinisk och experimentell medicin, Gastroenterologi och hepatologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Hjärt- och Medicincentrum, Endokrin- och magtarmmedicinska kliniken US.
    Mayer, Emeran
    UCLA, Los Angeles, USA.
    Walter, Susanna
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för klinisk och experimentell medicin, Gastroenterologi och hepatologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Hjärt- och Medicincentrum, Endokrin- och magtarmmedicinska kliniken US.
    Brain Responses to Visceral Stimuli Reflect Visceral Sensitivity Thresholds in Patients With Irritable Bowel Syndrome2012Ingår i: Gastroenterology, ISSN 0016-5085, E-ISSN 1528-0012, Vol. 142, nr 3, s. 463-472Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    BACKGROUND & AIMS:

    Only a fraction of patients with irritable bowel syndrome (IBS) have increased perceptual sensitivity to rectal distension, indicating differences in processing and/or modulation of visceral afferent signals. We investigated the brain mechanisms of these perceptual differences.

    METHODS:

    We analyzed data from 44 women with IBS and 20 female healthy subjects (controls). IBS symptom severity was determined by a severity scoring system. Anxiety and depression symptoms were assessed using the hospital anxiety and depression score. Blood oxygen level-dependent signals were measured by functional magnetic resonance imaging during expectation and delivery of high (45 mmHg) and low (15 mmHg) intensity rectal distensions. Perception thresholds to rectal distension were determined in the scanner. Brain imaging data were compared among 18 normosensitive and 15 hypersensitive patients with IBS and 18 controls. Results were reported significant if peak P-values were ≤.05, with family-wise error correction in regions of interest.

    RESULTS:

    The subgroups of patients with IBS were similar in age, symptom duration, psychological symptoms, and IBS symptom severity. Although brain responses to distension were similar between normosensitive patients and controls, hypersensitive patients with IBS had greater activation of insula and reduced deactivation in pregenual anterior cingulate cortex during noxious rectal distensions, compared to controls and normosensitive patients with IBS. During expectation of rectal distension, normosensitive patients with IBS had more activation in right hippocampus than controls.

    CONCLUSIONS:

    Despite similarities in symptoms, hyper- and normosensitive patients with IBS differ in cerebral responses to standardized rectal distensions and their expectation, consistent with differences in ascending visceral afferent input.

  • 142.
    Larsson, Peter
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
    Calibration of Ionization Chambers for Measuring Air Kerma Integrated over Beam Area in Diagnostic Radiology2006Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The air kerma area product PKA is an important quantity used by hospital physicists in quality assurance and optimization processes in diagnostic radiology and is recommended by national authorities for setting of diagnostic reference levels. PKA can be measured using a transmission ionization chamber (kerma area product (KAP) meter) mounted on the collimator housing. Its signal QKAP must be calibrated to give values of PKA. The objective of this thesis is to analyze the factors influencing the accuracy of the calibration coefficients k= PKA/QKAP and of reported PKA-values.

    Due to attenuation and scatter in the KAP-meter and presence of extra-focal radiation, values of PKA depend on the choice of integration area A and the distance of the reference plane from the focal spot yielding values of PKA that may differ by as much as 23% depending on this choice. The two extremes correspond to (1) PKA=PKA,o integrated over the exit surface of the KAP-meter resulting in geometry independent calibration coefficients and (2) PKA=PKA,Anom integrated over the nominal beam area in the patient entrance plane resulting in geometry dependent calibration coefficients.

    Three calibration methods are analysed. Method 1 aims at determine PKA,Anom, for clinical use at the patient entrance plane. At standard laboratories, the method is used to calibrate with respect to radiation incident on the KAP-meter. Problems with extra-focal and scattered radiation are then avoided resulting in calibration coefficients with low standard uncertainty (±1.5 %, coverage factor 2). Method 2 was designed in this work to approach determination of PKA,o using thermoluminescent detectors to monitor contributions from extra-focal radiation and account for the heel effect. The uncertainty in derived calibration coefficients was ± 3% (coverage factor 2). Method 3 uses a Master KAP-meter calibrated at a standard laboratory for incident radiation to calibrate clinical KAP-meters. It has potential to become the standard method in the future replacing the tedious method 2 for calibrations aiming at determination of PKA,o.

    Commercially available KAP-meters use conducting layers of indium oxide causing a strong energy dependence of their calibration coefficients. This dependence is investigated using Monte Carlo simulations and measurements. It may introduce substantial uncertainties in reported PKA– values since calibration coefficients as obtained from standard laboratories are often available only at one filtration (2.5 mm Al) as function of tube voltage or HVL. This is not sufficient since higher filtrations are commonly used in practice, including filters of Cu. In extreme cases, calibration coefficients for the same value of HVL but using different tube voltages and filtrations can deviate by as much as 30%. If standardised calibration methods are not used and choice of calibration coefficients not carefully chosen with respect to beam quality, the total uncertainty in reported PKA–values may be as large as 40-45%. Conversion of PKA-values to risk related quantities is briefly discussed. The large energy dependence of the conversion coefficients, ε/PKA, for determination of energy imparted,ε, to the patient reduces to a lower energy dependence of calibration coefficients CQ,ε = ε/QKAP for determination of ε from the KAP-meter signal.

    Delarbeten
    1. Transmission ionization chambers for measurements of air collision kerma integrated over beam area. Factors limiting the accuracy of calibration
    Öppna denna publikation i ny flik eller fönster >>Transmission ionization chambers for measurements of air collision kerma integrated over beam area. Factors limiting the accuracy of calibration
    1996 (Engelska)Ingår i: Physics in Medicine and Biology, ISSN 0031-9155, Vol. 41, nr 11, s. 2381-2398Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    Kerma - area product meters (KAP meters) are frequently used in diagnostic radiology to measure the integral of air-collision kerma over an area perpendicular to the x-ray beam. In this work, a precise method for calibrating a KAP meter to measure is described and calibration factors determined for a broad range of tube potentials (40 - 200 kV). The integral is determined using a large number of TL dosimeters spread over and outside the nominal field area defined as the area within 50% of maximum . The method is compared to a simplified calibration method which approximates the integral by multiplying the kerma in the centre of the field by the nominal field area . While the calibration factor using the precise method is independent of field area and distance from the source, that using the simplified method depends on both. This can be accounted for by field inhomogeneities caused by the heel effect, extrafocal radiation and scattered radiation from the KAP meter. The deviations between the calibration factors were as large as for collimator apertures of and distances from the source of 50 - 160 cm. The uncertainty in the calibration factor using the precise method was carefully evaluated and the expanded relative uncertainty estimated to be with a confidence level of 95%.

    Nationell ämneskategori
    Medicin och hälsovetenskap
    Identifikatorer
    urn:nbn:se:liu:diva-14174 (URN)10.1088/0031-9155/41/11/010 (DOI)
    Tillgänglig från: 2006-11-30 Skapad: 2006-11-30 Senast uppdaterad: 2015-03-20
    2. Evaluation of the uncertainties in KAP-meter calibrations
    Öppna denna publikation i ny flik eller fönster >>Evaluation of the uncertainties in KAP-meter calibrations
    1996 (Engelska)Rapport (Övrigt vetenskapligt)
    Abstract [en]

    This report was prepared in order to give more details to the uncertainty evaluation of the Kerma area product meter calibration procedure described in the paper:

    Larsson J P Persliden J Sandborg S and Alm Carlsson G 1996 Transmission ionization chambers for measurements of air collision kerma integrated over beam area. Factors limiting the accuracy of calibration. Phys. Med. Biol. 41 2381-2398.

    Figures and equations referred to in this report will be found in the paperabove.

    For convenience, however, the equations in the paper that are used in the uncertainty analysis are retyped on the next two sides, see text in section 2.7. in the paper for further details. The numbering of the equations are kept as in the paper.

    Ort, förlag, år, upplaga, sidor
    Linköping: Linköping University Electronic Press, 1996. s. 14
    Serie
    Report / Institutionen för radiofysik, Universitetet i Linköping, 1990-1997, ISSN 1102-1799 ; 82
    Nationell ämneskategori
    Radiologi och bildbehandling
    Identifikatorer
    urn:nbn:se:liu:diva-14175 (URN)LIU-RAD-R-082 (ISRN)91-7871-814-7 (ISBN)
    Tillgänglig från: 2006-11-30 Skapad: 2006-11-30 Senast uppdaterad: 2015-03-20Bibliografiskt granskad
    3. Ionization chambers for measuring air kerma integrated over beam area: Deviations in calibration values using simplified calibration methods
    Öppna denna publikation i ny flik eller fönster >>Ionization chambers for measuring air kerma integrated over beam area: Deviations in calibration values using simplified calibration methods
    1998 (Engelska)Ingår i: Physics in Medicine and Biology, ISSN 0031-9155, Vol. 43, nr 3, s. 599-607Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    Calibrations of kerma-area product meters (KAP meters) are often performed using simplified methods. The accuracy thus obtained can be insufficient, especially when the KAP meters are used for optimizing radiological procedures. The deviations between the best available calibration factor (k) and the simplified calibration factor were measured at different clinical x-ray installations. Depending on the type of x-ray installation and calibration method, the quotient ranged from 0.83 to 1.19, reflecting the error made in practice using these methods. A simple alternative calibration method based on comparison with a KAP meter calibrated by the best available method is described. Depending on tube potential and the stability of the electrometers, the uncertainty in the calibration factor derived with this method was between 3.8% and 5.6% (at 95% confidence level).

    Nationell ämneskategori
    Medicin och hälsovetenskap
    Identifikatorer
    urn:nbn:se:liu:diva-14176 (URN)10.1088/0031-9155/43/3/011 (DOI)
    Tillgänglig från: 2006-11-30 Skapad: 2006-11-30 Senast uppdaterad: 2015-03-20
    4. Monte Carlo study of the dependence of the KAP-meter calibration coefficient on beam aperture, X-ray tube voltage, and reference plane
    Öppna denna publikation i ny flik eller fönster >>Monte Carlo study of the dependence of the KAP-meter calibration coefficient on beam aperture, X-ray tube voltage, and reference plane
    2007 (Engelska)Ingår i: Physics in medicine and biology, ISSN 0031-9155, Vol. 52, nr 4, s. 1157-1170Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    The Monte Carlo method was used to study the dependence of the calibration coefficient on the tube voltage, beam aperture and reference plane in simplified over-couch geometries modelling VacuTec's type 70157 KAP-meter both with and without an additional filter. The MCNP5 code was used to calculate (i) energy imparted to air cavities of the KAP-meter and (ii) spatial distribution of air collision kerma at entrance and exit planes of the KAP-meter and at a plane close to the patient. From these data, the air kerma area product and calibration coefficient were calculated and their dependence on the tube voltage and beam aperture was analysed. It was found that the variation of the calibration coefficient as a function of tube voltage was up to 40% when the additional filter was used. The additional filter placed closely in front of the KAP-meter decreased the calibration coefficient for the patient plane by about 10% compared to the ideal additional filter. The effect of the beam aperture was small at the patient plane and negligible for the exit plane.

    Nationell ämneskategori
    Medicin och hälsovetenskap
    Identifikatorer
    urn:nbn:se:liu:diva-13034 (URN)10.1088/0031-9155/52/4/020 (DOI)
    Tillgänglig från: 2008-03-13 Skapad: 2008-03-13 Senast uppdaterad: 2015-03-20
    5. Energy dependence in KAP-meter calibration coefficients: Dependence on calibration method, type of KAP-meter, and added filter close to the KAP-meter
    Öppna denna publikation i ny flik eller fönster >>Energy dependence in KAP-meter calibration coefficients: Dependence on calibration method, type of KAP-meter, and added filter close to the KAP-meter
    2006 (Engelska)Ingår i: Physics in Medicine and Biology, ISSN 0031-9155, E-ISSN 1361-6560Artikel i tidskrift (Refereegranskat) Submitted
    Nationell ämneskategori
    Medicin och hälsovetenskap
    Identifikatorer
    urn:nbn:se:liu:diva-14178 (URN)
    Tillgänglig från: 2006-11-30 Skapad: 2006-11-30 Senast uppdaterad: 2017-12-13
  • 143.
    Larsson, Peter
    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.
    Evaluation of the uncertainties in KAP-meter calibrations1996Rapport (Övrigt vetenskapligt)
    Abstract [en]

    This report was prepared in order to give more details to the uncertainty evaluation of the Kerma area product meter calibration procedure described in the paper:

    Larsson J P Persliden J Sandborg S and Alm Carlsson G 1996 Transmission ionization chambers for measurements of air collision kerma integrated over beam area. Factors limiting the accuracy of calibration. Phys. Med. Biol. 41 2381-2398.

    Figures and equations referred to in this report will be found in the paperabove.

    For convenience, however, the equations in the paper that are used in the uncertainty analysis are retyped on the next two sides, see text in section 2.7. in the paper for further details. The numbering of the equations are kept as in the paper.

  • 144.
    Larsson, Peter
    et al.
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
    Malusek, Alexandr
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
    Persliden, Jan
    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.
    Energy dependence in KAP-meter calibration coefficients: Dependence on calibration method, type of KAP-meter, and added filter close to the KAP-meter2006Ingår i: Physics in Medicine and Biology, ISSN 0031-9155, E-ISSN 1361-6560Artikel i tidskrift (Refereegranskat)
  • 145.
    Larsson, Peter
    et al.
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
    Persliden, Jan
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Alm Carlsson, Gudrun
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Ionization chambers for measuring air kerma integrated over beam area: Deviations in calibration values using simplified calibration methods1998Ingår i: Physics in Medicine and Biology, ISSN 0031-9155, Vol. 43, nr 3, s. 599-607Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Calibrations of kerma-area product meters (KAP meters) are often performed using simplified methods. The accuracy thus obtained can be insufficient, especially when the KAP meters are used for optimizing radiological procedures. The deviations between the best available calibration factor (k) and the simplified calibration factor were measured at different clinical x-ray installations. Depending on the type of x-ray installation and calibration method, the quotient ranged from 0.83 to 1.19, reflecting the error made in practice using these methods. A simple alternative calibration method based on comparison with a KAP meter calibrated by the best available method is described. Depending on tube potential and the stability of the electrometers, the uncertainty in the calibration factor derived with this method was between 3.8% and 5.6% (at 95% confidence level).

  • 146.
    Larsson, Peter
    et al.
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
    Persliden, Jan
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Sandborg, Michael
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Alm Carlsson, Gudrun
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Transmission ionization chambers for measurements of air collision kerma integrated over beam area. Factors limiting the accuracy of calibration1996Ingår i: Physics in Medicine and Biology, ISSN 0031-9155, Vol. 41, nr 11, s. 2381-2398Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Kerma - area product meters (KAP meters) are frequently used in diagnostic radiology to measure the integral of air-collision kerma over an area perpendicular to the x-ray beam. In this work, a precise method for calibrating a KAP meter to measure is described and calibration factors determined for a broad range of tube potentials (40 - 200 kV). The integral is determined using a large number of TL dosimeters spread over and outside the nominal field area defined as the area within 50% of maximum . The method is compared to a simplified calibration method which approximates the integral by multiplying the kerma in the centre of the field by the nominal field area . While the calibration factor using the precise method is independent of field area and distance from the source, that using the simplified method depends on both. This can be accounted for by field inhomogeneities caused by the heel effect, extrafocal radiation and scattered radiation from the KAP meter. The deviations between the calibration factors were as large as for collimator apertures of and distances from the source of 50 - 160 cm. The uncertainty in the calibration factor using the precise method was carefully evaluated and the expanded relative uncertainty estimated to be with a confidence level of 95%.

  • 147.
    Leinhard, Olof Dahlqvist
    et al.
    Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Hälsouniversitetet.
    Johansson, Andreas
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
    Rydell, Joakim
    Linköpings universitet, Institutionen för medicinsk teknik, Medicinsk informatik. Linköpings universitet, Tekniska högskolan. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV.
    Smedby, Örjan
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Bildmedicinskt centrum, Röntgenkliniken i Linköping.
    Nystöm, Fredrik
    Linköpings universitet, Institutionen för medicin och hälsa, Internmedicin. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Medicincentrum, Endokrin- och magtarmmedicinska kliniken US.
    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.
    Borga, Magnus
    Linköpings universitet, Institutionen för medicinsk teknik, Medicinsk informatik. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Tekniska högskolan.
    Quantitative Abdominal Fat Estimation Using MRI2008Ingår i: Proceedings - International Conference on Pattern Recognition, IEEE Computer Society, 2008, s. 1-4Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper introduces a new method for automaticquantification of subcutaneous, visceral and nonvisceralinternal fat from MR-images acquired usingthe two point Dixon technique in the abdominal region.The method includes (1) a three dimensionalphase unwrapping to provide water and fat images, (2)an image intensity inhomogeneity correction, and (3) amorphon based registration and segmentation of thetissue. This is followed by an integration of the correctedfat images within the different fat compartmentsthat avoids the partial volume effects associated withtraditional fat segmentation methods. The method wastested on 18 subjects before and after a period of fastfoodhyper-alimentation showing high stability andperformance in all analysis steps.

  • 148.
    Lindborg, L
    et al.
    Karolinska Institute, Sweden .
    Hultqvist, M
    Stockholm University, Sweden .
    Carlsson Tedgren, Åsa
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Centrum för kirurgi, ortopedi och cancervård, Radiofysikavdelningen US.
    Nikjoo, H
    Karolinska Institute, Sweden .
    Lineal energy and radiation quality in radiation therapy: model calculations and comparison with experiment2013Ingår i: Physics in Medicine and Biology, ISSN 0031-9155, E-ISSN 1361-6560, Vol. 58, nr 10, s. 3089-3105Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Microdosimetry is a recommended method for characterizing radiation quality in situations when the biological effectiveness under test is not well known. In such situations, the radiation beams are described by their lineal energy probability distributions. Results from radiobiological investigations in the beams are then used to establish response functions that relate the lineal energy to the relative biological effectiveness (RBE). In this paper we present the influence of the size of the simulated volume on the relation to the clinical RBE values (or weighting factors). A single event probability distribution of the lineal energy is approximated by its dose average lineal energy ((y) over bar (D)) which can be measured or calculated for volumes from a few micrometres down to a few nanometres. The clinical RBE values were approximated as the ratio of the alpha-values derived from the LQ-relation. Model calculations are presented and discussed for the SOBP of a C-12 ion (290 MeV u(-1)) and the reference Co-60 gamma therapy beam. Results were compared with those for a conventional x-ray therapy beam, a 290 MeV proton beam and a neutron therapy beam. It is concluded that for a simulated volume of about 10 nm, the alpha-ratio increases approximately linearly with the (y) over bar (D)-ratio for all the investigated beams. The correlation between y and alpha provides the evidence to characterize a radiation therapy beam by the lineal energy when, for instance, weighting factors are to be estimated.

  • 149.
    Lindström, Jan
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
    Radioluminescence: A simple model for fluorescent layers2011Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The aim of this thesis is to present a simple model for the radiation to light conversion processes in fluorescent layers as an aid in future developments and applications. Optimisation between sensitivity and spatial resolution for fluorescent layers in digital radiology is a delicate task where the extrinsic efficiency for various phosphors needs to be established for varying parameters. The extrinsic efficiency of a fluorescent layer can be expressed as the ratio of the light energy per unit area at the screen surface to the incident xray energy fluence. Particle size is a critical factor in determining the value of the extrinsic efficiency, but in most models it is not treated as an independent variable. Based on the definition of a light extinction factor (ξ), a model is proposed such that, knowing the intrinsic efficiency η, the particle size and the thickness of a certain make of screen, the extrinsic efficiency can be calculated for an extended range of particle sizes and / or screen thicknesses. The light extinction factor ξ is an optical parameter determined from experimental data on extrinsic efficiency. The proposed model is compared to established methods. Further experiments have confirmed the validity of the model. Monte-Carlo simulations have been utilised to refine the calculations of energy imparted to the phosphor by taking into account the escape of scattered and K-radiation generated in the screen and interface effects at the surfaces. The luminance was measured for a set of in-house manufactured screens of varying thicknesses and particle sizes. Utilising the proposed model, the corresponding calculated values deviated ± 14 %.within the studied range.

    Delarbeten
    1. A simple model for estimating the particle size dependence of absolute efficiency of fluorescent screens
    Öppna denna publikation i ny flik eller fönster >>A simple model for estimating the particle size dependence of absolute efficiency of fluorescent screens
    1999 (Engelska)Ingår i: Physics in Medicine and Biology, ISSN 0031-9155, E-ISSN 1361-6560, Vol. 44, nr 5, s. 1353-67Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    The absolute efficiency of a phosphor screen is the ratio of the light energy per unit area at the screen surface to the incident x-ray energy fluence. Particle size is a critical factor in determining the absolute efficiency, but in most models its influence is not accounted for. To allow derivation of the particle size dependence, a model is proposed that describes the optical properties of the screen by means of a single parameter, the light extinction factor, xi, and assumes that the intrinsic efficiency (light energy/energy imparted to the phosphor material) is independent of particle size. The value of xi depends on the type of screen (phosphor, reflective backing, coating and binder) and has to be determined from measurements on at least two screens with known particle size and thickness. The absolute efficiency can then be calculated for an extended range of particle sizes and/or screen thicknesses. To test the model, experimental data from the literature were used to derive values of xi for screens of La2O2S:Tb, LaOBr:Tm and ZnCdS:Ag. The extinction factor was found to vary between -6 and +20%. The non-physical negative value for xi, found from one set of experiments on La2O2S:Tb screens, may be explained as resulting from a lack of accurate knowledge of the actual tube potential, influencing calculated values of the energy imparted to the screen. The results are promising but further well-controlled experiments (including improved dosimetric calculations to account forescape of K-radiation from the screen) are needed to confirm the model.

    Nationell ämneskategori
    Medicin och hälsovetenskap
    Identifikatorer
    urn:nbn:se:liu:diva-70537 (URN)doi:10.1088/0031-9155/44/5/319 (DOI)10368024 (PubMedID)
    Tillgänglig från: 2011-09-12 Skapad: 2011-09-12 Senast uppdaterad: 2017-12-08Bibliografiskt granskad
    2. Experimental verification of a model for estimating the particle size dependence of extrinsic efficiency of radioluminescent layers
    Öppna denna publikation i ny flik eller fönster >>Experimental verification of a model for estimating the particle size dependence of extrinsic efficiency of radioluminescent layers
    (Engelska)Manuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    The extrinsic (absolute) efficiency of a phosphor is expressed as the ratio of light energy emitted per unit area at the phosphor surface to incident x-ray energy fluence. Several studies on polycrystalline phosphor materials show that the optical parameters of a specific phosphor may vary within a wide range of values. The aim of this work was to verify a previously published model where all optical parameters were replaced with a single parameter, the light extinction factor ξ. The varying extrinsic efficiency for an extended range of particle sizes and layer thicknesses are calculated from the input parameters: the intrinsic efficiency η, the mean particle size of the phosphor, the thickness of the layer, the light extinction factor and the calculated energy imparted to the layer. The X-ray spectrum was simulated utilising the SpekCalc software (Poludniowski et al 2009). In this work, calculations of the energy imparted to in-house manufactured Gd2O2S:Tb screens, were also compared to calculations improved making use of Monte Carlo simulations (software PENELOPE (Baro et al 1995)). KAP (kerma area product) -rate-values were noted and the corresponding luminance measured and compared to calculated values. The deviations were ±14 % within the studied range.

    Nationell ämneskategori
    Medicin och hälsovetenskap
    Identifikatorer
    urn:nbn:se:liu:diva-70538 (URN)
    Tillgänglig från: 2011-09-12 Skapad: 2011-09-12 Senast uppdaterad: 2013-09-03Bibliografiskt granskad
  • 150.
    Lindström, Jan
    et al.
    Radiation Physics Department, Borås Hospital, Borås.
    Alm Carlsson, Gudrun
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Centrum för kirurgi, ortopedi och cancervård, Radiofysikavdelningen US.
    A simple model for estimating the particle size dependence of absolute efficiency of fluorescent screens1999Ingår i: Physics in Medicine and Biology, ISSN 0031-9155, E-ISSN 1361-6560, Vol. 44, nr 5, s. 1353-67Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The absolute efficiency of a phosphor screen is the ratio of the light energy per unit area at the screen surface to the incident x-ray energy fluence. Particle size is a critical factor in determining the absolute efficiency, but in most models its influence is not accounted for. To allow derivation of the particle size dependence, a model is proposed that describes the optical properties of the screen by means of a single parameter, the light extinction factor, xi, and assumes that the intrinsic efficiency (light energy/energy imparted to the phosphor material) is independent of particle size. The value of xi depends on the type of screen (phosphor, reflective backing, coating and binder) and has to be determined from measurements on at least two screens with known particle size and thickness. The absolute efficiency can then be calculated for an extended range of particle sizes and/or screen thicknesses. To test the model, experimental data from the literature were used to derive values of xi for screens of La2O2S:Tb, LaOBr:Tm and ZnCdS:Ag. The extinction factor was found to vary between -6 and +20%. The non-physical negative value for xi, found from one set of experiments on La2O2S:Tb screens, may be explained as resulting from a lack of accurate knowledge of the actual tube potential, influencing calculated values of the energy imparted to the screen. The results are promising but further well-controlled experiments (including improved dosimetric calculations to account forescape of K-radiation from the screen) are needed to confirm the model.

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