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  • 101.
    Lund, Eva
    et al.
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Medicinsk radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Gustafsson, Håkan
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Medicinsk radiofysik.
    Danilczuk, M
    Sastry, M
    Lund, Anders
    Linköpings universitet, Institutionen för fysik, kemi och biologi.
    Vestad, T-A
    Malinen, E
    Hole, E O
    Sagstuen, E
    Formates and dithionates: sensitive EPR dosimeter materialsfor radiation therapy2004Ingår i: Applied Radiation and Isotopes, ISSN 0969-8043, E-ISSN 1872-9800, Vol. 62, s. 317-324Artikel i tidskrift (Refereegranskat)
  • 102.
    Lund, Eva
    et al.
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Kyllönen, JE
    Grindborg, JE
    Lindborg, L
    Performance testing of personal dosemeters from eleven dosimetry services in Sweden2001Ingår i: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 96, nr 1-3, s. 99-103Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Swedish regulation, SSI FS 98:5, requires that radiological workers of category A use dosemeters from an approved personal dosimetry service. The 11 services operating in Sweden at the moment use five different types of dosemeter. All have been tested for their ability to determine Hp(10) and some of them to determine Hp(0.07) according to the European Commission report Radiation Protection 73, EUR 14852, of 1994. The five unique systems have been tested regarding the angular and energy dependence of the response of the dosemeters. The test points for the determination of Hp(10) are all, except one, within the trumpet curve and for the unique systems it is shown that the uncertainty related to angular response at three different energies is within the required ▒40% except for the lowest X ray quality 40 kV. The energy dependence dominates over the directional dependence and the choice of radiation quality for calibration is of great importance for the system performance.

  • 103.
    Lund, Eva
    et al.
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Medicinsk radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Wirell, Staffan
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Medicinsk radiologi.
    Salerud, Göran
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik.
    Basgruppsträffar gemensamma för teknologer och lärarstuderande inom ämnet "Radiologiska bilder"1997Ingår i: CUP-konferens,1997, 1997Konferensbidrag (Övrigt vetenskapligt)
  • 104.
    Lundberg, Peter
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Medicinsk radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Virtual Biochemistry Lab (NMR laboratory) http: //nobelprize.org/chemistry/educational/vbl/index.html2001Övrigt (Övrig (populärvetenskap, debatt, mm))
  • 105.
    Lundberg, Peter
    et al.
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Ekblad, Alf
    Nilsson, Mats
    13C NMR spectroscopy studies of forest soil microbial activity: Glucose uptake and fatty acid biosynthesis2001Ingår i: Soil Biology and Biochemistry, ISSN 0038-0717, E-ISSN 1879-3428, Vol. 33, nr 4-5, s. 621-632Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The intimate association of soil microorganisms with the soil matrix complicates analysis of their metabolism, since thorough separation of intact cells from the matrix is very difficult using standard protocols. Thus, in the study reported here, in situ glucose decomposition and metabolism in humus from a coniferous forest soil was monitored and evaluated using 'solution state' 13C NMR, which can be used in a non-invasive manner. [U-13C] glucose was added at a concentration of 1.73 mmol C g-1 dry organic matter, which is known to allow maximal substrate induced respiration (SIR), and the microbial metabolism of the added C was followed over a period of 28 days. The data showed that ~50% of the added glucose was consumed within three days, coinciding with the appearance of label in CH3, -CH2- and -CH = CH-groups, and in glycerol-carbons, suggesting that olefinic triacylglycerols were being formed, probably located in oil droplets. During days two to three, around 40% of the consumed glucose C was allocated into solid state components, about 40% was respired and about 20% was found as triglycerols. The triacylglycerol signal reached a maximum after 13 days, but subsequently declined by 60%, as the triacylglycerols were apparently consumed, by day 28 of the incubation. Our results indicate there was an initial formation of structural microbial C (solid state carbon) followed by formation of storage lipid C, which subsequently decreased, probably because it was used to provide the organisms with energy when the external energy source (i.e. the glucose) was depleted. The formation of unsaturated triacylglycerols, typical storage metabolites of eucaryotes, suggests that fungi were the most active organisms in the glucose degradation. ⌐ 2001 Elsevier Science Ltd.

  • 106.
    Lundberg, Peter
    et al.
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Lundquist, PO
    Primary metabolism in N-2-fixing Alnus incana-Frankia symbiotic root nodules studied with N-15 and P-31 nuclear magnetic resonance spectroscopy2004Ingår i: Planta, ISSN 0032-0935, E-ISSN 1432-2048, Vol. 219, nr 4, s. 661-672Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The primary nitrogen metabolism of the N-2-fixing root nodule symbiosis Alnus incana (L.)-Frankia was investigated by P-31 and N-15 nuclear magnetic resonance (NMR) spectroscopy. Perfusion of root nodules in a pulse-chase approach with N-15- or N-14-labeled NH4+ revealed the presence of the amino acids alanine (Ala), gamma-amino butyric acid, glutamine (Gln), glutamic acid (Glu), citrulline (Cit) and arginine (Arg). Labeling kinetics of the Gln amide-N and alpha-amino acids suggested that the glutamine synthetase (GS, EC 6.3.1.2)-glutamate synthase (GOGAT, EC 1.4.1.13) pathway was active. Inhibition of the GS-catalyzed reaction by methionine sulphoximine abolished incorporation of N-15. Cit was labeled in all three N positions but most rapidly in the omega position, consistent with carbamoyl phosphate as the precursor to which Gln could be the amino donor catalyzed by carbamoyl phosphate synthase (CPS, EC 6.3.5.5). Ala biosynthesis occurred consistent with a flux of N in the sequence Gln-Glu-Ala. P-31 NMR spectroscopy in vivo and of extracts revealed several metabolites and was used in connection with the N-15 pulse-chase experiment to assess general metabolic status. Stable concentrations of ATP and UDP-glucose during extended perfusions showed that the overall root nodule metabolism appeared undisturbed throughout the experiments. The metabolic pathways suggested by the NMR results were confirmed by high activities of the enzymes GS, NADH-GOGAT and ornithine carbamoyltransferase (OCT, EC 2.1.3.3). We conclude that the primary pathway of NH4+ assimilation in A. incana root nodules occurs through the GS-GOGAT pathway. Biosynthesis of Cit through GS-CPS-OCT is important and is a link between the first amino acid Gln and this final transport and storage form of nitrogen.

  • 107.
    Magnusson, Maria
    et al.
    Linköpings universitet, Institutionen för systemteknik, Bildbehandling. 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.
    Brynolfsson, Patrik
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
    Lundberg, Peter
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen. Östergötlands Läns Landsting, Bildmedicinskt centrum, Röntgenkliniken i Linköping.
    Improved temporal resolution in radial k-space sampling using an hourglass filter2009Ingår i: ISMRM 17th Scientific Meeting & Exhibition, Honolulu, Hawaii, USA, 2009Konferensbidrag (Refereegranskat)
    Abstract [en]

    Radial sampling of k-space is known to simultaneously provide both high spatial and high temporal resolution. Recently, an optimal radial profile time order based on the Golden Ratio was presented in [1]. We have adopted and modified the idea, with a focus onhigher temporal resolution without sacrificing any image quality.

    [1] Winkelmann et. al.: An optimal radial profile order based on the golden ratio for time-resolved MRI, IEEE Trans. Med. Im, Vol.26, No.1,2007.

  • 108.
    Magnusson, Maria
    et al.
    Linköpings universitet, Institutionen för systemteknik, Bildbehandling. 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.
    Brynolfsson, Patrik
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
    Lundberg, Peter
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen. Östergötlands Läns Landsting, Bildmedicinskt centrum, Röntgenkliniken i Linköping.
    Radial k-space sampling: step response using different filtering techniques2009Ingår i: ISMRM Workshop on Data sampling and Image Reconstruction, The Enchantment Resort, Sedona, Arizona, USA, 2009Konferensbidrag (Refereegranskat)
    Abstract [en]

    Radial sampling of k-space is known to simultaneously provide both high spatial and high temporal resolution. Recently, an optimalradial profile time order based on the Golden Ratio was presented in [1]. We have adopted and modified the idea, with a focus onhigher temporal resolution without sacrificing any image quality.

    [1] Winkelmann et. al.: An optimal radial profileorder based on the golden ratio for time-resolved MRI, IEEE Trans. Med. Im, Vol.26, No.1, 2007.

  • 109.
    Malmgren, Maine
    et al.
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Klinisk fysiologi. Östergötlands Läns Landsting, Hjärtcentrum, Fysiologiska kliniken.
    Hellerström, Sabine
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Klinisk fysiologi. Östergötlands Läns Landsting, Hjärtcentrum, Fysiologiska kliniken.
    Ekberg, Stefan
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Gustafsson, A
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Practical aspects on patient handling in 18F.FDG studies with dual-head coincidence gamma camera.2000Ingår i: Congress of the European Association of Nuclear Medicine, Paris 2000.,2000, 2000Konferensbidrag (Refereegranskat)
  • 110.
    Malusek, Alexandr
    et al.
    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. 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.
    Calculation of the energy absorption efficiency function of selected detector arrays using the MCNP code2007Rapport (Övrigt vetenskapligt)
    Abstract [en]

    This report describes a method for the calculation of the energy absorption efficiency function. It gives a theoretical justification of the method and presents results obtained using the MCNP4C code for (i) an infinite slab, (ii) a detector array without a collimator, and (iii) a detector array with a collimator. Moreover, it discusses an alternative method of scoring of the energy imparted per unit surface area in CTmod. This report is a supplement to the article “CTmod—a toolkit for Monte Carlo simulation of projections including scatter in computed tomography” by A. Malusek, M. Sandborg, and G. Alm Carlsson.

    Ladda ner fulltext (pdf)
    Calculation of the energy absorption efficiency function of selected detector arrays using the MCNP code
  • 111.
    Malusek, Alexandr
    et al.
    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. 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.
    CTmod: Mathematical Foundations2007Rapport (Övrigt vetenskapligt)
    Abstract [en]

    CTmod is a set of C++ class libraries primarily designed for the simulation of energy imparted to a CT-scanner detector array using the Monte Carlo method. This report describes mathematical methods and formulas that are used in the code. It is a supplement to the article “CTmod - a toolkit for Monte Carlo simulation of projections including scatter in computed tomography” by A. Malusek, M. Sandborg, and G. Alm Carlsson.

    In this report, random variables are denoted by a hat. For instance ˆx is a random variable and x is its sample. Points in space are denoted by bold capital letters, e.g. P. Directions are denoted by bold small letters, e.g. u. Inconsistencies in the current notation will be corrected in the next update of this report.

    Ladda ner fulltext (pdf)
    CTmod : Mathematical Foundations
  • 112.
    Malusek, Alexandr
    et al.
    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. 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.
    Simulation of scatter in cone beam CT – effects on projection image quality2003Ingår i: Proceedings of SPIE 5030: Medical Imaging 2003: Physics of Medical Imaging, Vol. 5030, s. 740-751Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Cone-beam computed tomography (CT) projections were calculated by the Monte Carlo method for two cylindrical water phantoms of different sizes and for an antropomorphic voxel phantom with and without the presence of an anti-scatter grid. The scatter-to-primary ratio (SPR) was evaluated for each projection and the dependence of the amount of scattered radiation on the phantom size, cone beam size, photon energy, and antiscatter grid was investigated. It was found that the amount of scattered radiation is a slowly varying function of position in the image plane whose values, depending on configuration parameters, may cover a range of several magnitudes. The SPR reflects changes in the amount of primary photons and may reach values around 5 for large phantoms, wide beams and 120 kV spectrum or even higher values for low energy photons.

  • 113.
    Malusek, Alexandr
    et al.
    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. 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.
    Validation of the CTmod toolkit2007Rapport (Övrigt vetenskapligt)
    Abstract [en]

    This report is a supplement to the article “CTmod—a toolkit for Monte Carlo simulation of projections including scatter in computed tomography” by A. Malusek, M. Sandborg, and G. Alm Carlsson. It describes methods that were used to validate the CTmod toolkit. Here, we adopt the terminology used in and: Verification is a process of determining whether or not the software is coded correctly and conforms to the specified requirements. Validation is a process of evaluating software to ensure compliance with physical applicability to the process being modelled. Validation of a code would consist of comparing it with known analytical solutions or against an already validated computer code, or could include benchmarking the code against relevant experimental data.

    CTmod is a toolkit implemented as a C++ class libray. A user is supposed to write a main program which uses classes from the toolkit. The main program is then compiled to create an executable. In this report, we tested two executables (ctmod1 and ctmod2) created this way. In chapter 2, scatter-to-primary ratios of air collision kerma calculated using ctmod1 are compared to data published in literature. In chapter 3, primary and scatter projections calculated using ctmod2 are compared to data calculated using the MCNP5 code. Though not related to the validation, we also report speeds of ctmod1 and ctmod2 as these were often requested from us.

    Ladda ner fulltext (pdf)
    Validation of the CTmod toolkit
  • 114. McVey, Graham
    et al.
    Sandborg, Michael
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Dance, David
    Alm Carlsson, Gudrun
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    A study and optimization of lumbar spine X-ray imaging systems2003Ingår i: British Journal of Radiology, ISSN 0007-1285, E-ISSN 1748-880X, Vol. 76, nr 903, s. 177-188Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A Monte Carlo program has been developed that incorporates a voxel phantom of an adult patient in a model of the complete X-ray imaging system, including the anti-scatter grid and screen-film receptor. This allows the realistic estimation of patient dose and the corresponding image (optical density map) for a wide range of equipment configurations. This paper focuses on the application of the program to lumbar spine anteroposterior and lateral screen-film examinations. The program has been applied to study the variation of physical image quality measures and effective dose for changing system parameters such as tube voltage, grid design and screen-film system speed. These variations form the basis for optimization of these system parameters. In our approach to optimization, the best systems are those that can match (or come close to) the calculated image quality measure of systems preferred in a recent European clinical trial, but with lower patient dose. The largest dose savings found were 21% for a 400 speed class system with a grid having a strip density of 40 cm-1 and a grid ratio of 16. A further dose saving of 13% was possible when a 600 speed class system was employed. The best systems found from the optimization correspond to those recommended by the European Commission guidelines on image quality criteria for diagnostic radiographic images.

  • 115. Moores, B
    et al.
    Mattsson, S
    Månsson, LG
    Panzer, W
    Regulla, D
    Dance, D
    Alm-Carlsson, Gudrun
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Medicinsk radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Verdun, F
    Buhr, E
    Hoeschen, C
    RADIUS - Closing the circle on the assessment of imaging performance2005Ingår i: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 114, nr 1-3, s. 450-457Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The RADIUS (Radiological Imaging Unification Strategy) project addresses the assessment of image quality in terms of both physical and clinically relevant measures. The aim is to unify our understanding of both types of measure as well as the numerous underlying factors that play a key role in the assessments of imaging performance. In this way it is expected to provide a solid basis for the improvement in radiological safety management, where not only radiation risks are considered but also diagnostic risks of incorrect clinical outcomes (i.e. false positive/false negative). The project has applied a variety of relevant experimental and theoretical methods to this problem, which is generic to medical imaging as a whole. Digital radiography of the chest and the breast has been employed as the clinical imaging domain vehicles for the study. The project addressed the problem from the following directions: role and relevance of pathology, human observer studies including receiver operating characteristics, image quality criteria analysis, structural noise analysis, physical measurements on clinical images, physical measurements on imaging system, modelling of imaging system, modelling of visual processes, modelling of doses delivered and IT-based scientific support strategies. This paper presents an overview of the main outcomes from this project and highlights how the research outcomes actually apply to the real world. In particular, attention will be focused on new and original findings and methods and techniques that have been developed within the framework of the project. The relevance of the project's outcomes to future European research will also be presented. © The Author 2005. Published by Oxford University Press. All rights reserved.

  • 116.
    Nilsson, Jonas
    et al.
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Lund, Eva
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Lund, Anders
    The effects of UV-irradiation on the ESR-dosimetry of tooth enamel2001Ingår i: Applied Radiation and Isotopes, ISSN 0969-8043, E-ISSN 1872-9800, Vol. 54, nr 1, s. 131-139Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Tooth enamel has been shown to be an excellent dosimeter material for retrospective dosimetry. A complication is that it is sensitive to ultraviolet light (UV), creating a signal that interferes with the dosimetric signal. Irradiation of tooth enamel by UV-light induces a mixture of stable and unstable free radicals. The unstable radicals disappear in about three weeks. Stable radicals are created both at the dosimetric peak and at the same g-value as the native peak. The stable peak coinciding with the native peak shows saturation behavior both for UVA/B- and UVC-light. The signal intensity from the sun is roughly estimated to induce a signal comparable to 15 mGy/h from 60 kV X-rays. The blue lamps used by dentists when hardening plastic repairs contain a narrow tail in the UVA/B-region, and it is shown here that these lamps also contribute to the stable peak coincident with the native peak. The contribution to the dosimetry peak, though negligible, at least for the irradiation times is used in this work. Most of the problems with UVA/B-induced signal contributions can probably be avoided by not using front teeth and teeth close to plastic repairs. (C) 2000 Elsevier Science Ltd.Tooth enamel has been shown to be an excellent dosimeter material for retrospective dosimetry. A complication is that it is sensitive to ultraviolet light (UV), creating a signal that interferes with the dosimetric signal. Irradiation of tooth enamel by UV-light induces a mixture of stable and unstable free radicals. The unstable radicals disappear in about three weeks. Stable radicals are created both at the dosimetric peak and at the same g-value as the native peak. The stable peak coinciding with the native peak shows saturation behavior both for UVA/B- and UVC-light. The signal intensity from the sun is roughly estimated to induce a signal comparable to 15 mGy/h from 60 kV X-rays. The blue lamps used by dentists when hardening plastic repairs contain a narrow tail in the UVA/B-region, and it is shown here that these lamps also contribute to the stable peak coincident with the native peak. The contribution to the dosimetry peak, though negligible, at least for the irradiation times is used in this work. Most of the problems with UVA/B-induced signal contributions can probably be avoided by not using front teeth and teeth close to plastic repairs.

  • 117.
    Norberg, Pernilla
    et al.
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen. Linköpings universitet, Hälsouniversitetet.
    Bake, Björn
    Sahlgrenska universitetssjukhuset, Göteborg.
    Jacobsson, Lars
    Göteborgs universitet, Göteborg.
    Alm Carlsson, Gudrun
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Gustafsson, Agnetha
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen. Linköpings universitet, Hälsouniversitetet.
    Evaluation of reconstruction techniques for lung single photon emission tomography: A Monte Carlo study2007Ingår i: Nuclear medicine communications, ISSN 0143-3636, E-ISSN 1473-5628, Vol. 28, nr 12, s. 929-936Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    BACKGROUND: In studies of the distribution of lung function, the image quality of lung single photon emission computed tomography (SPECT) is important and one factor influencing it is the reconstruction algorithm. AIM: To systematically evaluate ordered subsets expectation maximization (OSEM) and compare it with filtered back-projection (FBP) for lung SPECT with Tc. METHODS: The evaluation of the number of iterations used in OSEM was based on the image quality parameter contrast. The comparison between OSEM and FBP was based on trade-off plots between statistical noise and spatial resolution for different filter parameters, collimators and count-levels. A Monte Carlo technique was used to simulate SPECT studies of a digital thorax phantom containing two sets of activity: one with a homogeneous activity distribution within the lungs and the other with superposed high- and low-activity objects. Statistical noise in the reconstructed images was calculated as the coefficient of variation (CV) and spatial resolution as full width at half-maximum (FWHM). RESULTS: For the configuration studied, the OSEM reconstruction in combination with post-filtering should be used in lung SPECT studies with at least 60 MLEM equivalent iterations. Compared to FBP the spatial resolution was improved by about 1 mm. For a constant level of CV, a four-fold increase in count level resulted in an increased resolution of about 2 mm. Spatial resolution and cut-off frequency depends on what value of noise in the image is acceptable also increased by using a low-energy, high-resolution collimator for CV values above 3%. The choice of noise-reducing filter and cut-off frequency depends on what value of noise in the image is acceptable.

  • 118.
    Norberg Spaak, L
    et al.
    Östergötlands Läns Landsting, RC - Rekonstruktionscentrum, ÖNH - Öron- Näsa- Halskliniken.
    Granerus, Göran
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Klinisk fysiologi. Östergötlands Läns Landsting, Hjärtcentrum, Fysiologiska kliniken.
    Gustafsson, A
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    XVII World Congress IFOS Cairo, Egypt 2002Preliminary experiences of gamma camera-PET in patients with head and neck or lung cancer2002Ingår i: Rapportklass C eller D samt Impactvärde 0,000 sätts om ISSN inte kan uppges.,2002, 2002Konferensbidrag (Refereegranskat)
  • 119.
    Norrman, E.
    et al.
    Department of Natural Sciences, Örebro University, S-70182 Örebro, Sweden.
    Persliden, Jan
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    A factorial experiment on image quality and radiation dose2005Ingår i: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 114, nr 1-3, s. 246-252Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    To find if factorial experiments can be used in the optimisation of diagnostic imaging, a factorial experiment was performed to investigate some of the factors that influence image quality, kerma area product (KAP) and effective dose (E). In a factorial experiment the factors are varied together instead of one at a time, making it possible to discover interactions between the factors as well as major effects. The factors studied were tube potential, tube loading, focus size and filtration. Each factor was set to two levels (low and high). The influence of the factors on the response variables (image quality, KAP and E) was studied using a direct digital detector. The major effects of each factor on the response variables were estimated as well as the interaction effects between factors. The image quality, KAP and E were mainly influenced by tube loading, tube potential and filtration. There were some active interactions, for example, between tube potential and filtration and between tube loading and filtration. The study shows that factorial experiments can be used to predict the influence of various parameters on image quality and radiation dose. © The Author 2005. Published by Oxford University Press. All rights reserved.

  • 120.
    Norén, Bengt
    et al.
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiologi. 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, Medicinsk radiofysik. Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Bildmedicinskt centrum, Röntgenkliniken i Linköping. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Almer, Sven
    Linköpings universitet, Institutionen för klinisk och experimentell medicin, Gastroenterologi och hepatologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Medicincentrum, Endokrin- och magtarmmedicinska kliniken US.
    Kechagias, Stergios
    Linköpings universitet, Institutionen för medicin och hälsa, Internmedicin. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Medicincentrum, Endokrin- och magtarmmedicinska kliniken US.
    Ekstedt, Mattias
    Linköpings universitet, Institutionen för klinisk och experimentell medicin, Gastroenterologi och hepatologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Medicincentrum, Endokrin- och magtarmmedicinska kliniken US.
    Franzén, Lennart
    Medilab, Täby, Sweden.
    Wirell, Staffan
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiologi. Linköpings universitet, Hälsouniversitetet.
    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.
    Separation of advanced from mild fibrosis in diffuse liver disease using 31P magnetic resonance spectroscopy2008Ingår i: European Journal of Radiology, ISSN 0720-048X, E-ISSN 1872-7727, Vol. 66, nr 2, s. 313-320Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    31P-MRS using DRESS was used to compare absolute liver metabolite concentrations (PME, Pi, PDE, γATP, αATP, βATP) in two distinct groups of patients with chronic diffuse liver disorders, one group with steatosis (NAFLD) and none to moderate inflammation (n = 13), and one group with severe fibrosis or cirrhosis (n = 16). All patients underwent liver biopsy and extensive biochemical evaluation. A control group (n = 13) was also included. Absolute concentrations and the anabolic charge, AC = {PME}/({PME} + {PDE}), were calculated.

    Comparing the control and cirrhosis groups, lower concentrations of PDE (p = 0.025) and a higher AC (p < 0.001) were found in the cirrhosis group. Also compared to the NAFLD group, the cirrhosis group had lower concentrations of PDE (p = 0.01) and a higher AC (p = 0.009). No significant differences were found between the control and NAFLD group. When the MRS findings were related to the fibrosis stage obtained at biopsy, there were significant differences in PDE between stage F0–1 and stage F4 and in AC between stage F0–1 and stage F2–3.

    Using a PDE concentration of 10.5 mM as a cut-off value to discriminate between mild, F0–2, and advanced, F3–4, fibrosis the sensitivity and specificity were 81% and 69%, respectively. An AC cut-off value of 0.27 showed a sensitivity of 93% and a specificity of 54%.

    In conclusion, the results suggest that PDE is a marker of liver fibrosis, and that AC is a potentially clinically useful parameter in discriminating mild fibrosis from advanced.

  • 121.
    Norén, Bengt
    et al.
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Medicinsk radiologi. Östergötlands Läns Landsting, Bildmedicinskt centrum, Avdelningen för radiologi US.
    Lundberg, Peter
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Medicinsk radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV.
    Ressner, Marcus
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV.
    Wirell, Staffan
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Medicinsk radiologi.
    Almer, Sven
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för molekylär och klinisk medicin, Gastroenterologi och hepatologi. Östergötlands Läns Landsting, Medicincentrum, Endokrin- och magtarmmedicinska kliniken US.
    Smedby, Örjan
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Medicinsk radiologi. Östergötlands Läns Landsting, Bildmedicinskt centrum, Avdelningen för radiologi US. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV.
    Absolute quantification of human liver metabolite concentrations by localized in vivo 31P NMR spectroscopy in diffuse liver disease2005Ingår i: European Radiology, ISSN 0938-7994, E-ISSN 1432-1084, Vol. 15, nr 1, s. 148-157Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Phosphorus-31 NMR spectroscopy using slice selection (DRESS) was used to investigate the absolute concentrations of metabolites in the human liver. Absolute concentrations provide more specific biochemical information compared to spectrum integral ratios. Nine patients with histopathologically proven diffuse liver disease and 12 healthy individuals were examined in a 1.5-T MR scanner (GE Signa LX Echospeed plus). The metabolite concentration quantification procedures included: (1) determination of optimal depth for the in vivo measurements, (2) mapping the detection coil characteristics, (3) calculation of selected slice and liver volume ratios using simple segmentation procedures and (4) spectral analysis in the time domain. The patients had significantly lower concentrations of phosphodiesters (PDE), 6.3±3.9 mM, and ATP-β, 3.6±1.1 mM, (P<0.05) compared with the control group (10.0±4.2 mM and 4.2±0.3 mM, respectively). The concentrations of phosphomonoesters (PME) were higher in the patient group, although this was not significant. Constructing an anabolic charge (AC) based on absolute concentrations, [PME]/([PME] + [PDE]), the patients had a significantly larger AC than the control subjects, 0.29 vs. 0.16 (P<0.005). Absolute concentration measurements of phosphorus metabolites in the liver are feasible using a slice selective sequence, and the technique demonstrates significant differences between patients and healthy subjects.

  • 122.
    Norén, Bengt
    et al.
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Radiologi. Östergötlands Läns Landsting, Bildmedicinskt centrum, Avdelningen för radiologi US.
    Smedby, Örjan
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Radiologi. Östergötlands Läns Landsting, Bildmedicinskt centrum, Avdelningen för radiologi US. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV.
    Ressner, Marcus
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV.
    Lundberg, Peter
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV.
    Quantification of liver metabolites with phosphorus-31 Magnetic Resonance Spectroscopy2002Ingår i: European Congress of Radiology March 1-5, 2002,2002, 2002, s. 353-353Konferensbidrag (Refereegranskat)
  • 123.
    Ohlson, Maria
    et al.
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och hälsa. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Grétarsdóttir, Jakobína
    Sahlgrenska Universitetssjukhuset.
    Olsson, Eva
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och hälsa. Östergötlands Läns Landsting, Hjärtcentrum, Fysiologiska kliniken.
    Johansson, Lena
    Sahlgrenska Universitetssjukhuset.
    Gustafsson, Agneta
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och hälsa. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Kartläggning av bildkvalitet vid myokardscintifrafi: en nationell studie2008Rapport (Övrigt vetenskapligt)
    Abstract [sv]

     www.ssi.se Statens strålsskyddsinstitut Swedish Radiation Protection Authority.

  • 124.
    Olsson, Anna
    et al.
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Medicinsk radiofysik.
    Davidsson, Anette
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Klinisk fysiologi. Östergötlands Läns Landsting, Hjärtcentrum, Fysiologiska kliniken.
    Pettersson, Håkan
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Medicinsk radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Gustafsson, Agneta
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Medicinsk radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Finger doses from handling radioative isotopes at a Nuclear Medicine department2006Ingår i: EANM,2006, 2006Konferensbidrag (Övrigt vetenskapligt)
  • 125.
    Olsson, Anna
    et al.
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Medicinsk radiofysik.
    Gustafsson, Agneta
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Medicinsk radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Hellerström, Sabine
    Klinsik Fysiologi HC.
    Granerus, Göran
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Klinisk fysiologi. Östergötlands Läns Landsting, Hjärtcentrum, Fysiologiska kliniken.
    World Federation of Nuclear Medicine and Biology Santiago, Chile, 20022002Ingår i: World Federation of Nuclear Medicine and Biology Santiago, Chile 2002,2002, 2002Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

       

  • 126.
    Olsson, Anna
    et al.
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen. Linköpings universitet, Hälsouniversitetet.
    Ärlig, Åsa
    County Hospital Ryhov, Jönköping.
    Alm Carlsson, Gudrun
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Gustafsson, Agnetha
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen. Linköpings universitet, Hälsouniversitetet.
    Evaluation of reconstruction techniques in regional cerebral blood flow SPECT using trade-off plots: A Monte Carlo study2007Ingår i: Nuclear medicine communications, ISSN 0143-3636, E-ISSN 1473-5628, Vol. 28, nr 9, s. 719-725Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    BACKGROUND AND AIM: The image quality of single photon emission computed tomography (SPECT) depends on the reconstruction algorithm used. The purpose of the present study was to evaluate parameters in ordered subset expectation maximization (OSEM) and to compare systematically with filtered back-projection (FBP) for reconstruction of regional cerebral blood flow (rCBF) SPECT, incorporating attenuation and scatter correction. METHODS: The evaluation was based on the trade-off between contrast recovery and statistical noise using different sizes of subsets, number of iterations and filter parameters. Monte Carlo simulated SPECT studies of a digital human brain phantom were used. The contrast recovery was calculated as measured contrast divided by true contrast. Statistical noise in the reconstructed images was calculated as the coefficient of variation in pixel values. RESULTS: A constant contrast level was reached above 195 equivalent maximum likelihood expectation maximization iterations. The choice of subset size was not crucial as long as there were > or = 2 projections per subset. The OSEM reconstruction was found to give 5-14% higher contrast recovery than FBP for all clinically relevant noise levels in rCBF SPECT. The Butterworth filter, power 6, achieved the highest stable contrast recovery level at all clinically relevant noise levels. The cut-off frequency should be chosen according to the noise level accepted in the image. CONCLUSION: Trade-off plots are shown to be a practical way of deciding the number of iterations and subset size for the OSEM reconstruction and can be used for other examination types in nuclear medicine.

  • 127.
    Olsson, Sara
    Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Calibration of an alanine/agarose gel1998Rapport (Övrigt vetenskapligt)
    Abstract [en]

    In brachy therapy treatment, as well as in treatment with external beams, it is of crucial importance to thoroughly determine the absorbed dose in the tumour, in surrounding normal tissue and in risk organs.

    Several kinds of gel dosimeters have been, or are about to be, developed in order to get a three dimensional dosimeter, which would be very useful, especially in the context of brachy therapy. The need for high spatial resolution is raised by the fact that the absorbed dose decreases very fast with the distance from a brachy therapy source. The steep dose gradient also requires a dosimeter material with a wide dose range and no signal diffusion.

    Fe(II)/Fe(III) gel and polymer gels such as BANANA and BANG. These systems are analysed with magnetic resonance imaging (MRI) which gives a detailed picture with very high resolution (~0.5 mm) without the need to cut out samples and thereby destroy the geometry of the gel. One of the drawbacks for MRI-gels is that inhomogeneities in the magnetic field make it difficult to calibrate the gel in absolute values of absorbed dose.

    The Fe(II)/Fe(III) gel is the most well known of the gel dosimeters mentioned. The working principle is that it contains Fe(II)-ions that are oxidised to Fe(III)-ions when irradiated. The differences in paramagnetic properties between the ions can then be used to make an MRIimage of the dose distribution. The dose response is linear up to 40 Gy.

    The problem with this dosimeter type is the rapid diffusion of the Fe-ions which makes it necessary to image the gel immediately after irradiation to maintain the high resolution.

    In 1993 Maryanski et al. (Maryanski, 1993) reported a tissue-equivalent gel based on agarose, acrylamide and N,N´-methylene-bis-acrylamide (bis) in a de-aerated aqueous solution. The gel is called BANANA and works as a dosimeter due to the radiation induced polymerisation of the monomers acrylamide and bis. Later on, the agarose was replaced by gelatin because of its lower background signal. It is also more transparent which makes it easy to optically see the dose distribution since the polymerised gel volume changes to a white colour. This new gel is called BANG, and when further improved by substituting the acrylamide with acrylic acid it got the name BANG-2.

    The BANG-2 gel can measure doses down to 0.1 Gy which is much below the limit for both alanine gel and Fe(II/III) gel, but the dose response is only linear up to 6 Gy. Another drawback is the difficulties in preparing the gel. The preparation has to be made absolutely oxygen free since oxygen inhibits the polymerisation, and the gel must be stored in glass containers since most plastics are oxygen permeable. This puts great requirements on the preparation equipment, or the gel has to be bought, already cast in a predetermined shape. The glass container might also give some dosimetric effects since it has a higher atomic number than the gel itself.

    We have instead used a stiff agarose gel, heavily doped with alanine. The gel is heated and over saturated with alanine which recrystallizes when the gel is cooled down.

    When crystalline alanine is irradiated, radicals are formed which can be detected by means of electron spin resonance (ESR) spectroscopy. A signal proportional to the amount of radicals is then obtained. Since the amount of radicals is proportional to the absorbed dose, the substance may serve as a dosimeter material. The radicals in alanine are unusually stable because of the crystalline form, and in pure dry crystals the signal remains almost unchanged for several years.

    When the alanine is added to an agarose gel, the crystals are trapped in the gel which prevents signal diffusion. After irradiation, samples can be cut out at positions of interest. For the gel composition used in this work a sample weight of ~0.16 g is needed, which corresponds to a volume of ~0.12 cm3 (density: 1.28 g/ cm3). The shape of the sample can be chosen as convenient for the situation.

    The ESR analysis does not destroy the signal and thereby repeated read-outs of one sample are allowed.

    Alanine has a linear dose response from well below 1 Gy up to 104 Gy. The sensitivity when used in a gel allows doses down to ~3 Gy, as will be shown later on in this report.

    To make absolute dose measurements possible, as well as relative, the alanine/agarose gel requirescalibration.

    Absolute dose measurements are for example needed to verify Monte Carlo calculations experimentally. Dose planning systems used today do not take into account scattering effects at interfaces between materials of different atomic numbers, or scattering effects in a larger volume due to inserted shielding material. To verify that these simplifications do not set the outcome of the treatment at risk, and if possible to correct for the introduced errors, experimental measurements in such critical situations are needed.

    The aim of this report is to indicate a way of calibrating the alanine/agarose gel, and to examine the radical stability in the obtained calibration samples.

    Ladda ner fulltext (pdf)
    Calibration of an alanine/agarose gel
  • 128.
    Olsson, Sara
    et al.
    Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen. Linköpings universitet, Hälsouniversitetet.
    Bagherian, Shahrbanou
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Kemisk Fysik. Linköpings universitet, Hälsouniversitetet.
    Lund, Eva
    Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen. Linköpings universitet, Hälsouniversitetet.
    Alm Carlsson, Gudrun
    Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen. Linköpings universitet, Hälsouniversitetet.
    Lund, Anders
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Kemisk Fysik. Linköpings universitet, Tekniska högskolan.
    Ammonium tartrate as an ESR dosimeter material1999Ingår i: Applied Radiation and Isotopes, ISSN 0969-8043, E-ISSN 1872-9800, Vol. 50, nr 5, s. 955-965Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This study is one step in the search for an ESR dosimeter material with a higher signal intensity than the commonly used l-α-alanine, to be useful in the clinical dose range (approximately 0.1–20 Gy). The substance ammonium tartrate was found and investigated regarding signal intensity, radical stability, dose response and dose resolution. The ESR signal intensity of ammonium tartrate was shown to be more than twice the intensity of the alanine signal. The data indicate that an unstable radiation induced radical contributes to the ESR signal initially; after a couple of hours it has converted to a secondary radical which has a decay slow enough to be considered stable during the first two weeks after irradiation. Ammonium tartrate has a linear dose response in the investigated range of 0.5–4000 Gy and a dose resolution of 0.1 Gy at the 0.5 Gy level where, as a comparison, the corresponding value for alanine is 0.3 Gy. We thus find the substance suitable for clinical dosimetry.

  • 129.
    Olsson, Sara
    et al.
    Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Bergstrand, Eva S.
    Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Calibration of alanine dosimeters2001Rapport (Övrigt vetenskapligt)
    Abstract [en]

    In all kinds of radiation therapy it is of crucial importance to thoroughly determine the absorbed dose in the tumour, in surrounding normal tissue and in risk organs. This is done using various types of dosimeters, all with their advantages and disadvantages for different situations.

    Measurements of the dose distribution in a volume in terms of absolute absorbed dose are needed, for example to verify Monte Carlo calculations or clinical dose plans experimentally. To make such absolute dose measurements possible, the dosimeter requires calibration towards a dosimeter with a calibration factor that is traceable to a primary standard dosimetry laboratory. To not put the outcome of a radiation treatment at risk, the uncertainty in the absorbed dose determination at points of interest must not be higher than 5% (1 standard deviation) according to the ICRU (1976).

    The aim of this report is to indicate a way of calibrating two types of L-a-alanine dosimeters, an alanine/agarose gel and thin alanine films. The influence of some factors on the ESR signal from the alanine dosimeters is investigated, and suggestions are made on how to take these factors into account.

    Ladda ner fulltext (pdf)
    Calibration of alanine dosimeters
  • 130.
    Olsson, Sara
    et al.
    Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen. Linköpings universitet, Hälsouniversitetet.
    Bergstrand, Eva S.
    Department of Physics, University of Oslo, Norway.
    Carlsson, Åsa K.
    Medical Radiation Physics, Stockholm University and Karolinska Institute, Stockholm, Sweden.
    Hole, Eli O.
    Department of Physics, University of Oslo, Norway.
    Lund, Eva
    Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen. Linköpings universitet, Hälsouniversitetet.
    Radiation dose measurements with alanine/agarose gel and thin alanine films around a 192Ir brachytherapy source, using ESR spectroscopy2002Ingår i: Physics in Medicine and Biology, ISSN 0031-9155, E-ISSN 1361-6560, Vol. 47, nr 8, s. 1333-1356Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Alanine/agarose gel and alanine films in stacks have been used for measurements of absorbed dose around an HDR 192Ir source in a vaginal cylinder-applicator, with and without a 180° tungsten shield. The gel and the films were analysed by means of ESR spectroscopy and calibrated against an ion chamber in a 4 MV photon beam to obtain absolute dose values. The gel serves as both dosimeter and phantom material, and the thin (130 μm) films are used to achieve an improved spatial resolution in the dose estimations.

    Experimental values were compared with Monte Carlo simulations using two different codes. Results from the measurements generally agree with the simulations to within 5%, for both the alanine/agarose gel and the alanine films.

  • 131.
    Olsson, Sara K.
    et al.
    Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen. Linköpings universitet, Hälsouniversitetet.
    Lund, Eva
    Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen. Linköpings universitet, Hälsouniversitetet.
    Lund, Anders
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Kemisk Fysik. Linköpings universitet, Tekniska högskolan.
    Development of ammonium tartrate as an ESR dosimeter material for clinical purposes2000Ingår i: Applied Radiation and Isotopes, ISSN 0969-8043, E-ISSN 1872-9800, Vol. 52, nr 5, s. 1235-1241Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The crystalline substance ammonium tartrate is investigated with respect to its suitability as a clinical dosimetry material. The properties investigated are: the radical stability for absorbed doses relevant for clinical use, the improvement in sensitivity when the crystals are deuterated and the linear electron tranfer (LET)-dependence. After photon irradiation to an absorbed dose of 20 Gy, the signal increases rapidly during the first 6 h. After this period, the changes are more moderate and can be corrected for. The signal-to-noise ratio of irradiated ammonium tartrate is twice the corresponding value of alanine. By deuterating the crystals, the sensitivity can be further improved by a factor of 1.4. As expected, the signal decreases with increasing LET of the radiation, but no changes in the spectrum shape was observed.

  • 132.
    Olsson, Sara
    et al.
    Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen. Linköpings universitet, Hälsouniversitetet.
    Sagstuen, Einar
    Department of Physics, University of Oslo, Oslo, Norway .
    Bonora, Marco
    Linköpings universitet, Institutionen för fysik, kemi och biologi. Linköpings universitet, Tekniska högskolan.
    Lund, Anders
    Linköpings universitet, Institutionen för fysik, kemi och biologi. Linköpings universitet, Tekniska högskolan.
    EPR Dosimetric Properties of 2-Methylalanine: EPR, ENDOR and FT-EPR Investigations2002Ingår i: Radiation Research, ISSN 0033-7587, E-ISSN 1938-5404, Vol. 157, nr 2, s. 113-121Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    To find an EPR dosimeter material that is sensitive enough for clinical use, the substance 2-methylalanine (2MA) with the chemical structure (CH3)2C(NH3+)COO was tested for its sensitivity to ionizing radiation, dose response, and radical stability over time. At equal and moderate settings of microwave power and modulation amplitude, 2MA was found to be 70% more sensitive than l-α-alanine, which is the most common EPR dosimeter material today. The dose response is linear, at least in the dose range of interest (0.5–100 Gy), and the time-dependent variations in signal intensity are very small and may be corrected for easily. The energy dependence of the stopping power and energy absorption was calculated and was found to be similar to that of alanine. The dependence of the signal intensity on microwave power and modulation amplitude was investigated, and the optimal settings were found to be 25 mW (Bruker ER 4102ST) and 12 gauss, respectively. Single crystals of 2MA were analyzed using ENDOR and ENDOR-induced EPR to identify the radiation-induced radicals that formed. Only one radical, in which the amino group is detached from the original molecule, was identified. This radical is obviously dominating and is apparently the only one relevant for dosimetry purposes. The complete set of coupling parameters for three hyperfine couplings is reported. The power saturation properties and spectral line width are ruled by the relaxation times T1 and T2. To determine the relaxation times of 2MA, pulsed EPR experiments were performed on single crystals. Two different values of T1 were obtained, one in the range 1–3 µs, shown to be of importance for the dosimetry properties, and another that is strongly anisotropic with a value between 10 and 35 µs that does not seem to affect the saturation behavior. T2 was estimated to be of the order of 200–300 ns.

  • 133.
    Palhagen, Sven E
    et al.
    Karolinska University.
    Ekberg, Stefan
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Walinder, Jan
    University of Gothenburg.
    Granerus, Ann-Kathrine
    Linköpings universitet, Institutionen för klinisk och experimentell medicin, Geriatrik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Närsjukvården i centrala Östergötland, Geriatriska kliniken.
    Granerus, Göran
    Linköpings universitet, Institutionen för medicin och hälsa, Klinisk fysiologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Hjärtcentrum, Fysiologiska kliniken.
    HMPAO SPECT in Parkinsons disease (PD) with major depression (MD) before and after antidepressant treatment2009Ingår i: JOURNAL OF NEUROLOGY, ISSN 0340-5354, Vol. 256, nr 9, s. 1510-1518Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Previously we suggested that major depression (MD) in Parkinsons disease (PD) could be an indication of a more advanced and widespread neurodegenerative process, as PD symptoms were more severe in those with depression. We also found a different antidepressant response with SSRI medication in PD patients with depression compared to depressed patients without PD. This indicates diverse underlying pathophysiological mechanisms. Investigations using single-photon emission computed tomography (SPECT), measuring regional cerebral blood flow (rCBF), may contribute to enlighten the neurobiological substrates linked to depressive symptoms. SPECT was performed in order to compare rCBF in MD patients with and without PD. The study included 11 MD patients with PD, 14 nondepressed PD patients and 12 MD patients without PD. All patients were followed for 12 weeks with repeated evaluation of depressive as well as PD symptoms. Anti-Parkinsonian treatment remained unchanged during the study. Antidepressant treatment with SSRI (citalopram) was given to all patients with MD. SPECT was performed before and after 12 weeks of antidepressant treatment. rCBF was found to differ between PD patients with and without MD, as well as between MD patients with and without PD, both at baseline and concerning the response to treatment with SSRI (citalopram). In patients with PD the rCBF was found to be decreased in preoccipital and occipital regions, a finding more common when PD was combined with MD. In summary, larger cortical areas were found to be involved in depressed PD patients, both with hyperactivity (reciprocal to basal degeneration in PD and maybe dopaminergic treatment) and with hypoactivity (probably due to organic lesions leading to hypoperfusion). These observations support our hypothesis that PD combined with MD is an expression of a more advanced and widespread neurodegenerative disorder.

  • 134.
    Pernicka, Frantisek
    et al.
    Vienna.
    Alm Carlsson, Gudrun
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Dance, David
    London.
    DeWerd, Larry
    Wisconsin.
    Kramer, Hans-Michael
    Braunschweig.
    Ng, Kwan-Hong
    Kuala Lumpur.
    Development of an internationl code of practice for dosimetry in x-ray diagnostic radiology.2001Ingår i: IAEA (International Atomic Energy Agency), ISSN 1563-0153, Vol. 1, s. 93-98Artikel i tidskrift (Övrigt vetenskapligt)
  • 135.
    Persliden, Jan
    Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Analys av filmkassation: Ett SSI-projekt1996Rapport (Övrigt vetenskapligt)
    Abstract [en]

    Reject analysis in a radiology department can play an important role in the quality assurance process. Reject analysis was performed in the Department of Radiology, University Hospital in Linköping, Sweden, during 22 weeks 1992 and 5 weeks 1994. Between the two occasions, an education and training program was carried through. The rejected films were classified acording to 6 criteria. The reject frequency was 9.9% before and 8.5% after. Faulty exposure and faulty positioning of the patient contributing with 53 % of all rejected films.

    It was shown that reject analysis can easily be carried through. Compared to reports from the literature, the level found here was neither high nor low. The decrease in reject frequency after the training program was low and probably not significant. Reducing the rejections results in reduced patient doses and lower costs for the films. However, too low frequencies may be an indication of accepting bad image quality and reduced diagnostic accuracy. In the future when digital equipment is more frequently introduced the rejection of films will decrease, but not necessarily the retakes. Here, measurements of mean absorbed doses to the patients may provide a better toal for quality assurance of the radiology department.

    Ladda ner fulltext (pdf)
    Analys av filmkassation : Ett SSI-projekt
  • 136.
    Persliden, Jan
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Digital radiology and the radiological protection of the patient2004Ingår i: European Radiology, Supplement, ISSN 1613-3749, Vol. 14, nr 1, s. 50-58Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The wide dynamic range of the digital detectors and the capabilities of post-processing allow obtaining more information from the radiographic images and avoiding retakes. Using phosphor plates in the image formation process, it has been possible to lower the dose to the patient. In digital radiography, several authors report the possibility to substantially lower the radiation dose to the patient while maintaining or even increasing the image quality. In conventional radiography, increased patient dose results in a dark image. In digital radiography the brightness of the image does not depend on patient dose. High patient doses can result in low-noise, high-contrast digital images, therefore, optimization of examinations is of vital importance in digital radiography. Special emphasis should be directed to paediatrics. The digital technique is very useful in reducing the dose both in fluoroscopy and radiography, however, special procedures for children are needed. © Springer-Verlag 2004.

  • 137.
    Persliden, Jan
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Medicinsk radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Patient and staff doses in interventional X-ray procedures in Sweden2005Ingår i: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 114, nr 1-3, s. 150-157Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Interventional procedures in radiology are of concern because of irradiation doses to the patients and also to the staff. A questionnaire sent to all radiology departments in Sweden showed that 11,350 procedures were performed annually 1996-1997. In a follow-up study, data from patient procedures were recorded. Type of procedure, dose-area product (DAP) values, fluoroscopy times, number of radiography series and patient data were recorded. For some procedures, staff doses were measured. Skin doses to the patients were also calculated where possible. Results: A total of 380 interventional procedures were described. The procedures were grouped into cranial, neck and thorax, intestine and abdominal, uro/genital and pelvis and extremities. DAP and fluoroscopy times (mean values) were 200 Gy cm2 for 57 min, 57 Gy cm2 for 16 min, 270 Gy cm2 for 35 min, 212 Gy cm2 for 37 min, 67 Gy cm2 for 21 min, respectively, for the named procedures. Maximum patient skin doses exceeded threshold values for erythema (2 Gy) in cranial, neck/thorax and intestine/abdominal procedures. Effective doses to the patients could be high, 200 mSv. Conclusion: It was found that patient doses could exceed threshold values for skin erythema (2 Gy) and temporary epilation (3 Gy). Hence, the procedures require immediate improvement. © The Author 2005. Published by Oxford University Press. All rights reserved.

  • 138.
    Persliden, Jan
    et al.
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Beckman, KW
    Örebro.
    Geijer, Håkan
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Radiologi.
    Andersson, T
    Örebro.
    Optimisation of the relationship of the dose-image quality for a new direct digital detector.2001Ingår i: Eur Radiol,2001, 2001, s. 279-279Konferensbidrag (Refereegranskat)
  • 139.
    Persliden, Jan
    et al.
    Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Helmrot, Ebba
    Ryhov Hospital.
    Hjort, Per
    Ryhov Hospital.
    Resjö, Margareta
    Linköpings universitet, Institutionen för medicin och vård, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
    Dose and image quality in the comparison of analogue and digital techniques in paediatric urology examinations.2004Ingår i: European Radiology, ISSN 0938-7994, E-ISSN 1432-1084, Vol. 14, nr 4, s. 638-644Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In paediatric radiology it has been recognised that children have a higher risk of developing cancer from the irradiation than adults (two to three times); therefore, increased attention has been directed towards the dose to the patient. In this study the effect on patient dose and image quality in replacing the exposure in micturating cystourethrography (MCUG) examinations with the stored fluoroscopy image has been investigated. In the intravenous urography (IVU) examination we compared analogue and digital image quality, but the dose measurements were performed on a phantom. Standard clinical X-ray equipment was used. Sixty-eight patients in each of two centres were studied for the MCUG. Doses were measured with a dose-area product (DAP) meter and the image quality was scored. A non-parametric statistical analysis was performed. For the IVU, a phantom was used in the dose measurements but clinical images were scored in the comparison between analogue and digital images. For the MCUG, replacing the exposure with stored fluoroscopy images lowered the DAP value from 0.77 to 0.50 Gy cm2. The image quality did not show any difference between the techniques; however, if reflux was to be graded, exposure was needed. For the IVU, the doses could be lowered by a factor of 3 using digital techniques. The image quality showed no statistical difference between the two techniques. There is a potential for a substantial dose reduction in both MUCG and IVU examinations using digital techniques.

  • 140.
    Persliden, Jan
    et al.
    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, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen. Linköpings universitet, Hälsouniversitetet.
    Conversion factors between the energy imparted to the patient and air collision kerma integrated over beam area in paediatric radiology1993Ingår i: Acta Radiologica, ISSN 0284-1851, E-ISSN 1600-0455, Vol. 34, s. 92-98Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    n/a

  • 141.
    Pettersson, Håkan
    et al.
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Amano, H
    Auyama, M
    Berzhonov, V I
    Chaykovskaya, E
    Chumichev, V B
    Chung, C S
    Anthropogenic radionuclides in sediments in the NW Pacific Ocean and its marginal seas.1999Ingår i: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 237, s. 213-238Artikel i tidskrift (Refereegranskat)
  • 142.
    Pettersson, Håkan
    et al.
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Fälth-Magnusson, Karin
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för klinisk och experimentell medicin, Pediatrik. Östergötlands Läns Landsting, Barn- och kvinnocentrum, Barn- och ungdomskliniken i Linköping.
    Persliden, Jan
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Scott, M.
    Department of Statistics, University of Glasgow, Glasgow G12 8QW, United Kingdom.
    Radiation risk and cost-benefit analysis of a paediatric radiology procedure: Results from a national study2005Ingår i: British Journal of Radiology, ISSN 0007-1285, E-ISSN 1748-880X, Vol. 78, nr 925, s. 34-38Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A national study was performed to investigate radiation doses and associated risks to patients during X-ray fluoroscopy-guided small intestinal biopsies in the investigation of coeliac disease. Thermoluminescent dosemeters (TLD) and questionnaires were sent to 42 of the 43 paediatric departments in Sweden performing these biopsies. During the study period (2 × 3 weeks) 257 biopsies were recorded, representing about 10% of annually performed paediatric investigations. The results show that the absorbed dose during biopsy ranged from 0.04 mGy to 23.8 mGy (mean 1.87 mGy). The fluoroscopy time ranged from 2 s to 663 s (mean 60 s). The collective dose from the procedure amounts to 4.7 manSv year-1. Thus, the annual excess cancer mortality, including severe hereditary effects, can be estimated at 0.6-0.7 cases per year. However, significant dose saving can be obtained by proper choice of sedation and biopsy equipment. © 2005 The British Institute of Radiology.

  • 143.
    Pettersson, Håkan
    et al.
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Helmrot, Ebba
    Sandborg, Michael
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Nilsson, Jonas
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Olsson, Sara
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Persliden, Jan
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Radiofysik.
    Cederlund, Torsten
    Prenatal radiation exposures at diagnostic procedures: mathods to identify exposed pregnant patients2002Ingår i: European IRPA Congress 2002, FlorensISBN 88-88648-09-7,2002, 2002Konferensbidrag (Refereegranskat)
  • 144.
    Pettersson, Håkan
    et al.
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen. Linköpings universitet, Hälsouniversitetet.
    Povinec, P. P.
    Osvath, I.
    Baxter, M. S.
    Ballestra, S.
    Carroll, J.
    Gastaud, J.
    Harms, I.
    Summary of IAEA-MEL's investigation of Kara Sea radioactivity and radiological assessment1997Ingår i: Marine Pollution Bulletin, ISSN 0025-326X, E-ISSN 1879-3363, Vol. 35, nr 7-12, s. 235-241Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    IAEA-MEL participated in five expeditions to the Kara Sea with the aim of assessing the radiological consequences of dumped radioactive wastes in the Novaya Zemlya Bays and Trough. The programme included sampling, in-situ underwater investigations, laboratory analyses of water, sediment and biota samples, the development of a marine radioactivity database, modelling and radiological assessment, the organization of intercomparison exercises and the evaluation of distribution coefficients. Radiometric investigations have shown that no radiologically significant environmental contamination has occurred. Leakages which have led to locally increased levels of radionuclides in sediment have only been observed in Stepovoy and Abrosimov Bays. Computer modelling results suggest that only radiological effects on local and regional scales may be of importance. The global radiological impact of the disposals in the Arctic Seas will be negligible.

  • 145.
    Pham, M K
    et al.
    IAEA.
    Betti, M
    IAEA.
    Povinec, P P
    Comenius University.
    Benmansour, M
    Centre Natl Energie Science and Tech Nucl, Rabat.
    Buenger, V
    Senatsverwaltung Gesundheit Umwelt and Verbraucher.
    Drefvelin, J
    Norwegian Radiation Protection Authority.
    Engeler, C
    WGMLA Radiochem.
    Flemal, J M
    Science Institute for Public Health.
    Gasco, C
    Centre Invest Energet MedioAmbient and Technology.
    Guillevic, J
    Institute Radioprotect and Surette Nucl.
    Gurriaran, R
    IRSN DEI STEME LMRE.
    Groening, M
    IAEA.
    Happel, J D
    University of Miami.
    Herrmann, J
    Bundesamt Seeschifffahrt and Hydrog.
    Klemola, S
    Radiat and Nucl Safety Author.
    Kloster, M
    Senatsverwaltung Gesundheit Umwelt and Verbraucher.
    Kanisch, G
    Johann Heinrich von Thunen Institute.
    Leonard, K
    Centre Environm Fisheries and Aquaculture Science.
    Long, S
    Radiol Protect Institute Ireland.
    Nielsen, S
    Riso Natl Lab.
    Oh, J-S
    Natl Oceanog Centre Southampton.
    Rieth, P U
    Johann Heinrich von Thunen Institute.
    Oestergren, I
    Swedish Radiat Safety Author.
    Pettersson, Håkan
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Pinhao, N
    Institute Tecnol and Nucl, Sacavem, Portugal .
    Pujol, L
    Centre Estudios Expt and Obras Publ.
    Sato, K
    Japan Chemistry Anal Centre.
    Schikowski, J
    University of Gottingen.
    Varga, Z
    Hungarian Academy of Science.
    P Vartti, V
    Radiat and Nucl Safety Author.
    Zheng, J
    Natl Institute Radiol Science.
    A certified reference material for radionuclides in the water sample from Irish Sea (IAEA-443)2011Ingår i: JOURNAL OF RADIOANALYTICAL AND NUCLEAR CHEMISTRY, ISSN 0236-5731, Vol. 288, nr 2, s. 603-611Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A new certified reference material (CRM) for radionuclides in sea water from the Irish sea (IAEA-443) is described and the results of the certification process are presented. Ten radionuclides (H-3, K-40, Sr-90, Cs-137, U-234, U-235, U-238, Pu-238, Pu239+240 and Am-241) have been certified, and information values on massic activities with 95% confidence intervals are given for four radionuclides (Th-230, Th-232, Pu-239 and Pu-240). Results for less frequently reported radionuclides (Tc-99, Th-228, Np-237 and Pu-241) are also reported. The CRM can be used for quality assurance/quality control of the analysis of radionuclides in water samples, for the development and validation of analytical methods and for training purposes. The material is available in 5 L units from IAEA (http://nucleus.iaea.org/rpst/index.htm).

  • 146. Povinec, P
    et al.
    Woodhead, D
    Blowers, D
    Bonfield, R
    Cooper, R
    Chen, M
    Dahlgaard, Q
    Dovleete, H
    Fox, C
    Pettersson, Håkan
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Marine radioactivity assessment of Mururoa and Fangataufa atolls.1999Ingår i: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 237, s. 249-267Artikel i tidskrift (Refereegranskat)
  • 147. Povinec, Pavel
    et al.
    Livingston, Hugh
    Shima, Shigeki
    et.al, et.al
    Pettersson, Håkan
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    IAEA' 97 expedition to the NW pacific ocean - results of oceanographic and radionuclide investigations of the water column.2003Ingår i: Deep-sea research. Part II, Topical studies in oceanography, ISSN 0967-0645, E-ISSN 1879-0100, Vol. 50, s. 2607-2637Artikel i tidskrift (Refereegranskat)
  • 148. Beställ onlineKöp publikationen >>
    Ragnehed, Mattias
    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. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Functional Magnetic Resonance Imaging for Clinical Diagnosis: Exploring and Improving the Examination Chain2009Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Functional Magnetic Resonance Imaging (fMRI) is a relatively new imaging technique, first reported in 1992, which enables mapping of brain functions with high spatial resolution. Functionally active areas are distinguished by a small signal increase mediated by changes in local blood oxygenation in response to neural activity. The ability to non-invasively map brain function and the large number of MRI scanners quickly made the method very popular, and fMRI have had a huge impact on the study of brain function, both in healthy and diseased subjects.

    The most common clinical application of fMRI is pre-surgical mapping of brain functions in order to optimise surgical interventions. The clinical fMRI examination procedure can be divided into four integrated parts: (1) patient preparation, (2) image acquisition, (3) image analysis and (4) clinical decision. In this thesis, important aspects of all parts of the fMRI examination procedure are explored with the aim to provide recommendations and methods for prosperous clinical usage of the technique.

    The most important results of the thesis were: (I) administration of low doses of diazepam to reduce anxiety did not invalidate fMRI mapping results of primary motor and language areas, (II) the choice of visual stimuli equipment can have severe impact on the mapping of visual areas, (III) three-dimensional fMRI imaging sequences did not perform better than two-dimensional imaging sequences, (IV) adaptive spatial filtering can improve the fMRI data analysis, (V) clinical decisions should not be based on activation results from a single statistical threshold.

    Delarbeten
    1. Influence of diazepam on clinically designed FMRI
    Öppna denna publikation i ny flik eller fönster >>Influence of diazepam on clinically designed FMRI
    Visa övriga...
    2007 (Engelska)Ingår i: The Journal of Neuropsychiatry and Clinical Neurosciences, ISSN 0895-0172, E-ISSN 1545-7222, Vol. 19, nr 2, s. 164-172Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    The authors investigated the effect of diazepam on clinically relevant measures from functional magnetic resonance imaging (fMRI) examinations. Twenty volunteers were scanned twice. Using a double-blind randomized study design, the volunteers received placebo on one occasion, and on the other, 5 mg of diazepam. Three functional tests were used: motor, word generation, and working memory. Images were analyzed individually for each subject and the number of activated voxels and the laterality index were calculated. No significant effects related to the drug were detected. In contrast, the motor and working memory tasks showed a significant decrease in the number of activated voxels between Sessions 1 and 2, independently of diazepam administration. These results indicate that diazepam may be administered for premedication prior to fMRI investigations.

    Nationell ämneskategori
    Medicin och hälsovetenskap
    Identifikatorer
    urn:nbn:se:liu:diva-17989 (URN)10.1176/appi.neuropsych.19.2.164 (DOI)000245666300009 ()17431063 (PubMedID)
    Tillgänglig från: 2009-04-30 Skapad: 2009-04-30 Senast uppdaterad: 2017-12-13Bibliografiskt granskad
    2. Projection screen or video goggles as stimulus modality in functional magnetic resonance imaging
    Öppna denna publikation i ny flik eller fönster >>Projection screen or video goggles as stimulus modality in functional magnetic resonance imaging
    2005 (Engelska)Ingår i: Magnetic Resonance Imaging, ISSN 0730-725X, E-ISSN 1873-5894, Vol. 23, nr 5, s. 695-699Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    The purpose of this study was to investigate the reliability of functional magnetic resonance imaging (fMRI) by using either a projection screen or video goggles as stimulus modality. A sequence of visual stimuli were presented to the same subject at different occasions. The sequence was optimized with a genetic algorithm. In five sessions the stimuli were presented using a projection screen viewed through a mirror in the head coil and in five sessions using video goggles. Failure to detect visual activation in the medial left hemisphere was observed in sessions using the projection screen as stimulus modality. Decreased thresholds for P values and cluster size resulted in activation outside the occipital lobe and did not significantly increase activated areas in this region. Results in this study indicate that presentation of fMRI tasks with visual routes is more reliable with direct input through video goggles than with the conventional use of projection screens. Failure to detect crucial visual areas has severe consequences for tumor surgery in the visual cortex. Inferior visual impression might also have negative consequences for cognitive tests with high demand on attention and perception.

    Nyckelord
    fMRI; Visual; Projection screen; Video goggles; Reliability
    Nationell ämneskategori
    Medicin och hälsovetenskap
    Identifikatorer
    urn:nbn:se:liu:diva-17992 (URN)10.1016/j.mri.2005.04.006 (DOI)16051046 (PubMedID)
    Tillgänglig från: 2009-04-30 Skapad: 2009-04-30 Senast uppdaterad: 2017-12-13Bibliografiskt granskad
    3. Visual Grading of 2D and 3D fMRI compared to image based descriptive measures
    Öppna denna publikation i ny flik eller fönster >>Visual Grading of 2D and 3D fMRI compared to image based descriptive measures
    Visa övriga...
    2010 (Engelska)Ingår i: European Radiology, ISSN 0938-7994, E-ISSN 1432-1084, Vol. 20, nr 3, s. 714-724Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    A prerequisite for successful clinical use of functional Magnetic Resonance Imaging (fMRI) is the selection of an appropriate imaging sequence. In this paper, 2D and 3D fMRI sequences were compared using different image quality assessment methods. Descriptive image measures, such as activation volume and temporal signal-to-noise ratio (TSNR), were compared with results from Visual Grading Characteristics (VGC) analysis of the fMRI results. It was found that significant differences in activation volume and TSNR were not directly reflected by differences in VGC scores. The results suggest that better performance on descriptive image measures is not always an indicator of improved diagnostic quality of the fMRI results. In conclusion, in addition to descriptive image measures, it is important to include measures of diagnostic quality when comparing different fMRI data acquisition methods.

    Ort, förlag, år, upplaga, sidor
    Berlin / Heidelberg: Springer, 2010
    Nationell ämneskategori
    Medicin och hälsovetenskap
    Identifikatorer
    urn:nbn:se:liu:diva-17994 (URN)10.1007/s00330-009-1578-0 (DOI)000274544800023 ()19727748 (PubMedID)
    Anmärkning

    The original publication is available at www.springerlink.com: Mattias Ragnehed, Olof Dahlqvist Leinhard, Johan Pihlsgård, Staffan Wirell, Hannibal Sökjer, Patrik Fägerstam, Bo Jiang, Örjan Smedby, Maria Engström and Peter Lundberg, Visual Grading of 2D and 3D fMRI compared to image based descriptive measures, 2010, European Radiology, (20), 3, 714-724. http://dx.doi.org/10.1007/s00330-009-1578-0 Copyright: Springer Science Business Media http://www.springerlink.com/

    Tillgänglig från: 2009-04-30 Skapad: 2009-04-30 Senast uppdaterad: 2019-06-14Bibliografiskt granskad
    4. Restricted Canonical Correlation Analysis in Functional MRI-Validation and a Novel Thresholding Technique
    Öppna denna publikation i ny flik eller fönster >>Restricted Canonical Correlation Analysis in Functional MRI-Validation and a Novel Thresholding Technique
    Visa övriga...
    2009 (Engelska)Ingår i: Journal of Magnetic Resonance Imaging, ISSN 1053-1807, E-ISSN 1522-2586, Vol. 29, nr 1, s. 146-154Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    Purpose: To validate the performance of an analysis method for fMRI data based on restricted canonical correlation analysis (rCCA) and adaptive filtering, and to increase the usability of the method by introducing a new technique for significance estimation of rCCA maps.

    Materials and Methods: Activation data from a language task and also a resting state fMRI data were collected from eight volunteers. Data was analyzed using both the rCCA method and the General Linear Model (GLM). A modified Receiver Operating Characteristic (ROC) method was used to evaluate the performance of the different analysis methods. The area under a fraction of the ROC curve was used as a measure of performance. On resting state data the fraction of voxels above certain significance thresholds were used to evaluate the significance estimation method.

    Results: The rCCA method scored significantly higher on the area under the ROC curve than the GLM. The fraction of activated voxels determined by thresholding according to the introduced significance estimation technique showed good agreement with the thresholds selected.

    Conclusion: The rCCA method is an effective analysis tool for fMRI data and its usability is increased with the introduced significance estimation method.

    Nyckelord
    fMRI, GLM, canonical correlation analysis, thresholding, significance
    Nationell ämneskategori
    Medicin och hälsovetenskap
    Identifikatorer
    urn:nbn:se:liu:diva-16411 (URN)10.1002/jmri.21494 (DOI)000262168200019 ()
    Tillgänglig från: 2009-01-23 Skapad: 2009-01-23 Senast uppdaterad: 2017-12-14Bibliografiskt granskad
    5. Right-hemispheric brain activation correlates to language performance
    Öppna denna publikation i ny flik eller fönster >>Right-hemispheric brain activation correlates to language performance
    Visa övriga...
    2010 (Engelska)Ingår i: NEUROIMAGE, ISSN 1053-8119, Vol. 49, nr 4, s. 3481-3488Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

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

    Nationell ämneskategori
    Medicin och hälsovetenskap
    Identifikatorer
    urn:nbn:se:liu:diva-53932 (URN)10.1016/j.neuroimage.2009.10.041 (DOI)000274064500059 ()
    Anmärkning
    Original Publication: Helene M van Ettinger-Veenstra, Mattias Ragnehed, Mathias Hällgren, Thomas Karlsson, Anne-Marie Landtblom, Peter Lundberg and Maria Engström, Right-hemispheric brain activation correlates to language performance, 2010, NEUROIMAGE, (49), 4, 3481-3488. http://dx.doi.org/10.1016/j.neuroimage.2009.10.041 Copyright: Elsevier Science B.V., Amsterdam http://www.elsevier.com/Tillgänglig från: 2010-02-12 Skapad: 2010-02-12 Senast uppdaterad: 2014-10-02
    Ladda ner fulltext (pdf)
    Functional Magnetic Resonance Imaging for Clinical Diagnosis
    Ladda ner (pdf)
    Cover
    Ladda ner (pdf)
    POPULARSUMMARY01
  • 149.
    Ragnehed, Mattias
    et al.
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiologi. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Hälsouniversitetet.
    Dahlqvist Leinhard, Olof
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Hälsouniversitetet.
    Pihlsgård, Johan
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Hälsouniversitetet.
    Wirell, Staffan
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiologi. Linköpings universitet, Hälsouniversitetet.
    Sökjer, Hannibal
    Linköpings universitet, Institutionen för datavetenskap, MDI - Interaction and Service Design Research Group. Linköpings universitet, Tekniska högskolan.
    Fägerstam, Patrik
    Linköpings universitet, Institutionen för medicin och hälsa, Farmakologi. Linköpings universitet, Hälsouniversitetet.
    Jiang, Bo
    Linköpings universitet, Institutionen för medicin och hälsa. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Hälsouniversitetet.
    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.
    Engström, Maria
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiologi. Linköpings universitet, Hälsouniversitetet.
    Lundberg, Peter
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen. Östergötlands Läns Landsting, Bildmedicinskt centrum, Röntgenkliniken i Linköping.
    Visual Grading of 2D and 3D fMRI compared to image based descriptive measures2010Ingår i: European Radiology, ISSN 0938-7994, E-ISSN 1432-1084, Vol. 20, nr 3, s. 714-724Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A prerequisite for successful clinical use of functional Magnetic Resonance Imaging (fMRI) is the selection of an appropriate imaging sequence. In this paper, 2D and 3D fMRI sequences were compared using different image quality assessment methods. Descriptive image measures, such as activation volume and temporal signal-to-noise ratio (TSNR), were compared with results from Visual Grading Characteristics (VGC) analysis of the fMRI results. It was found that significant differences in activation volume and TSNR were not directly reflected by differences in VGC scores. The results suggest that better performance on descriptive image measures is not always an indicator of improved diagnostic quality of the fMRI results. In conclusion, in addition to descriptive image measures, it is important to include measures of diagnostic quality when comparing different fMRI data acquisition methods.

    Ladda ner fulltext (pdf)
    FULLTEXT01
  • 150.
    Ragnehed, Mattias
    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.
    Engström, Maria
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiologi. Linköpings universitet, Hälsouniversitetet.
    Knutsson, Hans
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik. Linköpings universitet, Tekniska högskolan.
    Axelsson Söderfeldt, Birgitta
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för klinisk och experimentell medicin, Neurologi. Linköpings universitet, Hälsouniversitetet. 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.
    Restricted Canonical Correlation Analysis in Functional MRI-Validation and a Novel Thresholding Technique2009Ingår i: Journal of Magnetic Resonance Imaging, ISSN 1053-1807, E-ISSN 1522-2586, Vol. 29, nr 1, s. 146-154Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Purpose: To validate the performance of an analysis method for fMRI data based on restricted canonical correlation analysis (rCCA) and adaptive filtering, and to increase the usability of the method by introducing a new technique for significance estimation of rCCA maps.

    Materials and Methods: Activation data from a language task and also a resting state fMRI data were collected from eight volunteers. Data was analyzed using both the rCCA method and the General Linear Model (GLM). A modified Receiver Operating Characteristic (ROC) method was used to evaluate the performance of the different analysis methods. The area under a fraction of the ROC curve was used as a measure of performance. On resting state data the fraction of voxels above certain significance thresholds were used to evaluate the significance estimation method.

    Results: The rCCA method scored significantly higher on the area under the ROC curve than the GLM. The fraction of activated voxels determined by thresholding according to the introduced significance estimation technique showed good agreement with the thresholds selected.

    Conclusion: The rCCA method is an effective analysis tool for fMRI data and its usability is increased with the introduced significance estimation method.

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