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  • 1.
    Aalto, Anne
    et al.
    Linköping University, Department of Medicine and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences.
    Dahlqvist Leinhard, Olof
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medicine and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Jaworski, M
    Gustavsson, M
    Tisell, Anders
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medicine and Health Sciences, Radiation Physics. Östergötlands Läns Landsting, Centre for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics UHL. Linköping University, Faculty of Health Sciences.
    Landtblom, Anne-Marie
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Clinical and Experimental Medicine, Psychiatry. Östergötlands Läns Landsting, Sinnescentrum, Department of Neurosurgery UHL. Linköping University, Faculty of Health Sciences.
    Lundberg, Peter
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medicine and Health Sciences, Radiation Physics. Linköping University, Department of Medicine and Health Sciences, Radiology. Östergötlands Läns Landsting, Centre for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics UHL. Östergötlands Läns Landsting, Centre for Diagnostics, Department of Radiology in Linköping. Linköping University, Faculty of Health Sciences.
    Smedby, Örjan
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medicine and Health Sciences, Radiology. Östergötlands Läns Landsting, Centre for Diagnostics, Department of Radiology in Linköping. Linköping University, Faculty of Health Sciences.
    Effects of Betainterferon treatment in Multiple Sclerosis Studied by Quantitative 1H MRS2009Conference paper (Other academic)
  • 2.
    Adolfsson, Emelie
    et al.
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Alm Carlsson, Gudrun
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics.
    Grindborg, Jan-Erik
    Statens Strålskyddsinstitut, Stockholm.
    Gustafsson, Håkan
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Lund, Eva
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Carlsson Tedgren, Åsa
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics.
    Response of Lithium Formate EPR Dosimeters at Photon Energies Relelvant to Brachytherapy2009In: IFMBE Proceedings, Heidelberg: Springer Berlin Heidelberg , 2009, p. 236-239Conference paper (Other academic)
    Abstract [en]

    After development of sensitive dosimeter materials Electron Paramagnetic Resonance EPR dosimetry has been successfully used also in radiation therapy. The intensity of the EPR-signal is a measure of the amount of free radicals created by ionizing radiation which is proportional to the absorbed dose in the dosimeter. Lithium formate monohydrate is a dosimeter material with 2-6 times higher sensitivity than alanine, a linear dose response over a wide dose range and mass-energy absorption properties similar to water. These properties make lithium formate promising for verification of absorbed doses around high dose rate brachytherapy sources where the dose gradient is steep and the photon energy distribution changing with distance from the source. Calibration of the dosimeters is performed in 60Co or MV photon beams where high dosimetric accuracy is feasible. The use in brachytherapy field relies on the assumption that the production of free radicals per mean absorbed dose in the dosimeter is similar at the lower photon energies present there. The aim of this work was to test that assumption. The response of the dosimeters as a function of photon energy was determined by irradiations with four x-ray qualities in the range 100-250 kV and 137Cs, relative to the response when irradiated with 60Co, all photon beams with well-known air kerma rates at the Swedish Secondary Standards Dosimetry Laboratory. Monte Carlo simulations were used to convert air kerma free in air to mean absorbed dose to the dosimeter. The measured response relative 60Co as a function of photon energy was below unity for all qualities. The maximum deviation from unity was 2.5% (100 kV, 135 kV) with a relative standard deviation of 1.5% (k = 1).

  • 3.
    Adolfsson, Emelie
    et al.
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Alm Carlsson, Gudrun
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics.
    Grindborg, Jan-Erik
    Swedish Radiation Safety Authority, Stockholm, Sweden .
    Gustafsson, Håkan
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Lund, Eva
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Carlsson Tedgren, Åsa
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics. Swedish Radiation Safety Authority, Stockholm, Sweden .
    Response of lithium formate EPR dosimeters at photon energies relevant to the dosimetry of brachytherapy2010In: Medical physics (Lancaster), ISSN 0094-2405, Vol. 37, no 9, p. 4946-4959Article in journal (Refereed)
    Abstract [en]

    PURPOSE:

    To investigate experimentally the energy dependence of the detector response of lithium formate EPR dosimeters for photon energies below 1 MeV relative to that at 60Co energies. High energy photon beams are used in calibrating dosimeters for use in brachytherapy since the absorbed dose to water can be determined with high accuracy in such beams using calibrated ion chambers and standard dosimetry protocols. In addition to any differences in mass-energy absorption properties between water and detector, variations in radiation yield (detector response) with radiation quality, caused by differences in the density of ionization in the energy imparted (LET), may exist. Knowledge of an eventual deviation in detector response with photon energy is important for attaining high accuracy in measured brachytherapy dose distributions.

    METHODS:

    Lithium formate EPR dosimeters were irradiated to known levels of air kerma in 25-250 kV x-ray beams and in 137Cs and 60Co beams at the Swedish Secondary Standards Dosimetry Laboratory. Conversions from air kerma free in air into values of mean absorbed dose to the detectors were made using EGSnrc MC simulations and x-ray energy spectra measured or calculated for the actual beams. The signals from the detectors were measured using EPR spectrometry. Detector response (the EPR signal per mean absorbed dose to the detector) relative to that for 60Co was determined for each beam quality.

    RESULTS:

    Significant decreases in the relative response ranging from 5% to 6% were seen for x-ray beams at tube voltages < or = 180 kV. No significant reduction in the relative response was seen for 137Cs and 250 kV x rays.

    CONCLUSIONS:

    When calibrated in 60Co or MV photon beams, corrections for the photon energy dependence of detector response are needed to achieve the highest accuracy when using lithium formate EPR dosimeters for measuring absorbed doses around brachytherapy sources emitting photons in the energy range of 20-150 keV such as 169Yb and electronic sources.

  • 4.
    Adolfsson, Emelie
    et al.
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Karlsson, Mattias
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences.
    Alm Carlsson, Gudrun
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics.
    Carlsson Tedgren, Åsa
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics. Swedish Radiation Safety Authority, Stockholm, Sweden .
    Lund, Eva
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Olsson, Sara
    Central Hospital Växjö, Sweden.
    Gustafsson, Håkan
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Investigation of signal fading in lithium formate EPR dosimeters using a new sensitive method2012In: Physics in Medicine and Biology, ISSN 0031-9155, E-ISSN 1361-6560, Vol. 57, no 8, p. 2209-2217Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to investigate signal fading in lithium formate electron paramagnetic resonance (EPR) dosimeters used for clinical applications in radiotherapy. A new experimental method for determination of signal fading, designed to resolve small changes in signal from slowly decaying unstable radicals, was used. Possible signal fading in lithium formate due to different storage temperatures was also tested. Air humidity was kept at a constant level of 33% throughout the experiments. The conclusion drawn from the investigations was that the EPR signal from lithium formate is stable during at least 1 month after irradiation and is not sensitive to variations in storage temperature andlt;40 degrees C when kept at a relative air humidity of 33%. This makes lithium formate a suitable dosimeter for transfer dosimetry in clinical audits.

  • 5.
    Ahlman, Gustav
    et al.
    Linköping University, Department of Electrical Engineering, Computer Vision. Linköping University, The Institute of Technology.
    Magnusson, Maria
    Linköping University, Department of Electrical Engineering, Computer Vision. Linköping University, The Institute of Technology.
    Dahlqvist Leinhard, Olof
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Lundberg, Peter
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Increased temporal resolution in radial-Cartesian sampling of k-space by implementation of parallel imaging2011Conference paper (Refereed)
  • 6.
    Andersson, Mats
    et al.
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Biomedical Engineering, Medical Informatics. Linköping University, The Institute of Technology.
    Smedby, Örjan
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Sandborg, Michael
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics.
    Farnebäck, Gunnar
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Biomedical Engineering, Medical Informatics. Linköping University, The Institute of Technology.
    Hans, Knutsson
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Biomedical Engineering, Medical Informatics. Linköping University, The Institute of Technology.
    Adaptiv filtering of 4D-heart CT for image denoising and patient safety2010Conference paper (Other academic)
    Abstract [en]

    The aim of this medical image science project is to increase patient safety in terms of improved image quality and reduced exposure to ionizing radiation in CT. The means to achieve these goals is to develop and evaluate an efficient adaptive filtering (denoising/image enhancement) method that fully explores true 4D image acquisition modes. Four-dimensional (4D) medical image data are captured as a time sequence of image volumes. During 4D image acquisition, a 3D image of the patient is recorded at regular time intervals. The resulting data will consequently have three spatial dimensions and one temporal dimension. Increasing the dimensionality of the data impose a major increase the computational demands. The initial linear filtering which is the cornerstone in all adaptive image enhancement algorithms increase exponentially with the dimensionality. On the other hand the potential gain in Signal to Noise Ratio (SNR) also increase exponentially with the dimensionality. This means that the same gain in noise reduction that can be attained by performing the adaptive filtering in 3D as opposed to 2D can be expected to occur once more by moving from 3D to 4D. The initial tests on on both synthetic and clinical 4D images has resulted in a significant reduction of the noise level and an increased detail compared to 2D and 3D methods. When tuning the parameters for adaptive filtering is extremely important to attain maximal diagnostic value which not necessarily coincide with an an eye pleasing image for a layman. Although this application focus on CT the resulting adaptive filtering methods will be beneficial for a wide range of 3D/4D medical imaging modalities e.g. shorter acquisition time in MRI and improved elimination of noise in 3D or 4D ultrasound datasets.

  • 7.
    Andersson, Thord
    et al.
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Biomedical Engineering, Medical Informatics. Linköping University, The Institute of Technology.
    Romu, Thobias
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Biomedical Engineering, Medical Informatics. Linköping University, The Institute of Technology.
    Norén, Bengt
    Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Forsgren, Mikael
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics.
    Smedby, Örjan
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Almer, Sven
    Linköping University, Department of Clinical and Experimental Medicine, Gastroenterology and Hepatology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Endocrinology.
    Lundberg, Peter
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics.
    Borga, Magnus
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Biomedical Engineering, Medical Informatics. Linköping University, The Institute of Technology.
    Dahlqvist Leinhard, Olof
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Self-calibrated DCE MRI using Multi Scale Adaptive Normalized Averaging (MANA)2012In: Proceedings of the annual meeting of the International Society for Magnetic Resonance in Medicine (ISMRM 2012), 2012, 2012Conference paper (Other academic)
  • 8.
    Antonovic, Laura
    et al.
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences.
    Gustafsson, Håkan
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Alm Carlsson, Gudrun
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics.
    Carlsson Tedgren, Åsa
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics.
    Evaluation of a lithium formate EPR dosimetry system for dose measurements around Ir-192 brachytherapy sources2009In: MEDICAL PHYSICS, ISSN 0094-2405, Vol. 36, no 6, p. 2236-2247Article in journal (Refereed)
    Abstract [en]

    A dosimetry system using lithium formate monohydrate (HCO2Li center dot H2O) as detector material and electron paramagnetic resonance (EPR) spectroscopy for readout has been used to measure absorbed dose distributions around clinical Ir-192 sources. Cylindrical tablets with diameter of 4.5 mm, height of 4.8 mm, and density of 1.26 g/cm(3) were manufactured. Homogeneity test and calibration of the dosimeters were performed in a 6 MV photon beam. Ir-192 irradiations were performed in a PMMA phantom using two different source models, the GammaMed Plus HDR and the microSelectron PDR-v1 model. Measured absorbed doses to water in the PMMA phantom were converted to the corresponding absorbed doses to water in water phantoms of dimensions used by the treatment planning systems (TPSs) using correction factors explicitly derived for this experiment. Experimentally determined absorbed doses agreed with the absorbed doses to water calculated by the TPS to within +/- 2.9%. Relative standard uncertainties in the experimentally determined absorbed doses were estimated to be within the range of 1.7%-1.3% depending on the radial distance from the source, the type of source (HDR or PDR), and the particular absorbed doses used. This work shows that a lithium formate dosimetry system is well suited for measurements of absorbed dose to water around clinical HDR and PDR Ir-192 sources. Being less energy dependent than the commonly used thermoluminescent lithium fluoride (LiF) dosimeters, lithium formate monohydrate dosimeters are well suited to measure absorbed doses in situations where the energy dependence cannot easily be accounted for such as in multiple-source irradiations to verify treatment plans. Their wide dynamic range and linear dose response over the dose interval of 0.2-1000 Gy make them suitable for measurements on sources of the strengths used in clinical applications. The dosimeter size needs, however, to be reduced for application to single-source dosimetry.

  • 9.
    Antonsson, Johan
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Eriksson, Ola
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Lundberg, Peter
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Wårdell, Karin
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Optical measurements during experimental stereotactic radiofrequency lesioning2006In: Stereotactic and Functional Neurosurgery, ISSN 1011-6125, E-ISSN 1423-0372, Vol. 84, no 2-3, p. 118-124Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to evaluate in vivo a laser Doppler measurement system in porcine brain tissue during thermal lesioning. A 2-mm monopolar radiofrequency lesioning electrode was equipped with optical fibers in order to monitor the lesioning procedure. Laser Doppler and backscattered light intensity signals were measured along the electrode trajectory and during bilateral lesioning in the central gray (70, 80 and 90°C, n = 14). The time course of the coagulation process could be followed by optical recordings. Two separate groups of tissue were identified from the intensity signals. The changes in the perfusion levels in both groups displayed significant changes (p < 0.05, n = 48) at all temperature settings, while backscattered light intensity was significant for only one group at the different temperatures (p < 0.05, n = 39). These results indicate that optical measurements correlate with lesion development in vivo. The study also indicates that it is possible to follow the lesioning process intra-operatively.

  • 10.
    Baranowski, Jacek
    et al.
    Östergötlands Läns Landsting, Heart and Medicine Centre, Department of Clinical Physiology UHL.
    Ahn, Henrik
    Linköping University, Department of Medical and Health Sciences, Thoracic Surgery. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Centre, Department of Thoracic and Vascular Surgery in Östergötland.
    Freter, Wolfgang
    Östergötlands Läns Landsting, Heart and Medicine Centre, Department of Thoracic and Vascular Surgery in Östergötland.
    Nielsen, Niels-Erik
    Linköping University, Department of Medical and Health Sciences, Cardiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Centre, Department of Cardiology UHL.
    Nylander, Eva
    Linköping University, Department of Medical and Health Sciences, Clinical Physiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Centre, Department of Clinical Physiology UHL.
    Janerot-Sjöberg, Birgitta
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology. Östergötlands Läns Landsting, Heart and Medicine Centre, Department of Clinical Physiology UHL.
    Sandborg, Michael
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics UHL.
    Wallby, Lars
    Linköping University, Department of Medical and Health Sciences, Cardiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Centre, Department of Clinical Physiology UHL.
    Echo-guided presentation of the aortic valve minimises contrast exposure in transcatheter valve recipients2011In: Catheterization and cardiovascular interventions, ISSN 1522-1946, E-ISSN 1522-726X, Vol. 77, no 2, p. 272-275Article in journal (Refereed)
    Abstract [en]

    OBJECTIVES:

    We have developed a method using transthoracic echocardiography in establishing optimal visualization of the aortic root, to reduce the amount of contrast medium used in each patient.

    BACKGROUND:

    During transcatheter aortic valve implantation, it is necessary to obtain an optimal fluoroscopic projection for deployment of the valve showing the aortic ostium with the three cusps aligned in the beam direction. This may require repeat aortic root angiograms at this stage of the procedure with a high amount of contrast medium with a risk of detrimental influence on renal function.

    METHODS:

    We studied the conventional way and an echo guided way to optimize visualisation of the aortic root. Echocardiography was used initially allowing easier alignment of the image intensifier with the transducer's direction.

    RESULTS:

    Contrast volumes, radiation/fluoroscopy exposure times, and postoperative creatinine levels were significantly less in patients having the echo-guided orientation of the optimal fluoroscopic angles compared with patients treated with the conventional approach.

    CONCLUSION:

    We present a user-friendly echo-guided method to facilitate fluoroscopy adjustment during transcatheter aortic valve implantation. In our series, the amounts of contrast medium and radiation have been significantly reduced, with a concomitant reduction in detrimental effects on renal function in the early postoperative phase.

  • 11.
    Beaulieu, Luc
    et al.
    Centre hospitalier universitaire de Québec, Canada and Université Laval, Québec, Canada .
    Carlsson Tedgren, Åsa
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Carrier, Jean-François
    Centre hospitalier de l’Université de Montréal, Québec, Canada and Département de physique, Université de Montréal, Québec Canada .
    Davis, Stephen D.
    University of Wisconsin-Madison, USA and McGill University Health Centre, Montréal, Québec, Canada .
    Mourtada, Firas
    Helen F. Graham Cancer Center, Christiana Care Health System, Newark, Delaware, USA.
    Rivard, Mark J.
    Tufts University School of Medicine, Boston, Massachusetts, USA.
    Thomson, Rowan M.
    Carleton University, Ottawa, Ontario, Canada.
    Verhaegen, Frank
    Maastricht University Medical Center, the Netherlands and McGill University Health Centre, Montréal, Québec, Canada .
    Wareing, Todd A.
    Transpire Inc., Gig Harbor, Washington, USA.
    Williamson, Jeffrey F.
    Virginia Commonwealth University, Richmond, USA.
    Report of the Task Group 186 on model-based dose calculation methods in brachytherapy beyond the TG-43 formalism: Current status and recommendations for clinical implementation2012In: Medical physics (Lancaster), ISSN 0094-2405, Vol. 39, no 10, p. 6208-6236Article in journal (Refereed)
    Abstract [en]

    The charge of Task Group 186 (TG-186) is to provide guidance for early adopters of model-based dose calculation algorithms (MBDCAs) for brachytherapy (BT) dose calculations to ensure practice uniformity. Contrary to external beam radiotherapy, heterogeneity correction algorithms have only recently been made available to the BT community. Yet, BT dose calculation accuracy is highly dependent on scatter conditions and photoelectric effect cross-sections relative to water. In specific situations, differences between the current water-based BT dose calculation formalism (TG-43) and MBDCAs can lead to differences in calculated doses exceeding a factor of 10. MBDCAs raise three major issues that are not addressed by current guidance documents: (1) MBDCA calculated doses are sensitive to the dose specification medium, resulting in energy-dependent differences between dose calculated to water in a homogeneous water geometry (TG-43), dose calculated to the local medium in the heterogeneous medium, and the intermediate scenario of dose calculated to a small volume of water in the heterogeneous medium. (2) MBDCA doses are sensitive to voxel-by-voxel interaction cross sections. Neither conventional single-energy CT nor ICRU∕ICRP tissue composition compilations provide useful guidance for the task of assigning interaction cross sections to each voxel. (3) Since each patient-source-applicator combination is unique, having reference data for each possible combination to benchmark MBDCAs is an impractical strategy. Hence, a new commissioning process is required. TG-186 addresses in detail the above issues through the literature review and provides explicit recommendations based on the current state of knowledge. TG-43-based dose prescription and dose calculation remain in effect, with MBDCA dose reporting performed in parallel when available. In using MBDCAs, it is recommended that the radiation transport should be performed in the heterogeneous medium and, at minimum, the dose to the local medium be reported along with the TG-43 calculated doses. Assignments of voxel-by-voxel cross sections represent a particular challenge. Electron density information is readily extracted from CT imaging, but cannot be used to distinguish between different materials having the same density. Therefore, a recommendation is made to use a number of standardized materials to maintain uniformity across institutions. Sensitivity analysis shows that this recommendation offers increased accuracy over TG-43. MBDCA commissioning will share commonalities with current TG-43-based systems, but in addition there will be algorithm-specific tasks. Two levels of commissioning are recommended: reproducing TG-43 dose parameters and testing the advanced capabilities of MBDCAs. For validation of heterogeneity and scatter conditions, MBDCAs should mimic the 3D dose distributions from reference virtual geometries. Potential changes in BT dose prescriptions and MBDCA limitations are discussed. When data required for full MBDCA implementation are insufficient, interim recommendations are made and potential areas of research are identified. Application of TG-186 guidance should retain practice uniformity in transitioning from the TG-43 to the MBDCA approach.

  • 12.
    Blystad, Ida
    et al.
    Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Diagnostics, Department of Radiology in Linköping.
    Warntjes, Jan Bertus Marcel
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medical and Health Sciences, Clinical Physiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Centre, Department of Clinical Physiology UHL.
    Smedby, Örjan
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Diagnostics, Department of Radiology in Linköping.
    Landtblom, Anne-Marie
    Linköping University, Department of Clinical and Experimental Medicine, Neurology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Local Health Care Services in Central Östergötland, Department of Neurology. Linköping University, Center for Medical Image Science and Visualization, CMIV.
    Lundberg, Peter
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics UHL.
    SyntheticMRI compared with conventional MRI of the brain in a clinical setting: a pilot study, ESMRMB 2012, Lisbon, Portugal.2012Conference paper (Other academic)
  • 13.
    Blystad, Ida
    et al.
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences.
    Warntjes, Jan Bertus Marcel
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Clinical Physiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Clinical Physiology in Linköping.
    Smedby, Örjan
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Landtblom, Anne-Marie
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Clinical and Experimental Medicine, Neurology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Local Health Care Services in Central Östergötland, Department of Neurology.
    Lundberg, Peter
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics.
    Larsson, Elna-Marie
    Uppsala University, Sweden .
    Synthetic MRI of the brain in a clinical setting2012In: Acta Radiologica, ISSN 0284-1851, E-ISSN 1600-0455, Vol. 53, no 10, p. 1158-1163Article in journal (Refereed)
    Abstract [en]

    BACKGROUND:

    Conventional magnetic resonance imaging (MRI) has relatively long scan times for routine examinations, and the signal intensity of the images is related to the specific MR scanner settings. Due to scanner imperfections and automatic optimizations, it is impossible to compare images in terms of absolute image intensity. Synthetic MRI, a method to generate conventional images based on MR quantification, potentially both decreases examination time and enables quantitative measurements.

    PURPOSE:

    To evaluate synthetic MRI of the brain in a clinical setting by assessment of the contrast, the contrast-to-noise ratio (CNR), and the diagnostic quality compared with conventional MR images.

    MATERIAL AND METHODS:

    Twenty-two patients had synthetic imaging added to their clinical MR examination. In each patient, 12 regions of interest were placed in the brain images to measure contrast and CNR. Furthermore, general image quality, probable diagnosis, and lesion conspicuity were investigated.

    RESULTS:

    Synthetic T1-weighted turbo spin echo and T2-weighted turbo spin echo images had higher contrast but also a higher level of noise, resulting in a similar CNR compared with conventional images. Synthetic T2-weighted FLAIR images had lower contrast and a higher level of noise, which led to a lower CNR. Synthetic images were generally assessed to be of inferior image quality, but agreed with the clinical diagnosis to the same extent as the conventional images. Lesion conspicuity was higher in the synthetic T1-weighted images, which also had a better agreement with the clinical diagnoses than the conventional T1-weighted images.

    CONCLUSION:

    Synthetic MR can potentially shorten the MR examination time. Even though the image quality is perceived to be inferior, synthetic images agreed with the clinical diagnosis to the same extent as the conventional images in this study.

  • 14.
    Blystad, Ida
    et al.
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping. Linköping University, Department of Medical and Health Sciences, Radiology.
    Warntjes, Marcel
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Clinical Physiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Clinical Physiology in Linköping.
    Helmersson, Teresa
    Linköping University, Department of Medical and Health Sciences. Linköping University, Faculty of Health Sciences.
    Lundberg, Peter
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Contrast assessment of Synthetic Magnetic Resonance Imaging in clinical practice2011Conference paper (Refereed)
  • 15.
    Borga, Magnus
    et al.
    Linköping University, Department of Biomedical Engineering, Medical Informatics. Linköping University, The Institute of Technology. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Friman, Ola
    Linköping University, Department of Biomedical Engineering, Medical Informatics. Linköping University, The Institute of Technology.
    Lundberg, Peter
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics.
    Knutsson, Hans
    Linköping University, Department of Biomedical Engineering, Medical Informatics. Linköping University, The Institute of Technology.
    A canonical correlation approach to exploratory data analysis in fMRI2002Conference paper (Other academic)
    Abstract [en]

    A computationally efficient data-driven method for exploratory analysis of functional MRI data is presented. The basic idea is to reveal underlying components in the fMRI data that have maximum autocorrelation. The tool for accomplishing this task is Canonical Correlation Analysis. The proposed method is more robust and much more computationally efficient than independent component analysis, which previously has been applied in fMRI.

  • 16.
    Borgen, Lars
    et al.
    Drammen and Buskerud University of College.
    Kalra, Mannudeep K
    Harvard University.
    Laerum, Frode
    Akershus University Hospital.
    Hachette, Isabelle W
    ContextVision AB.
    Fredriksson, Carina H
    ContextVision AB, Linkoping, Sweden .
    Sandborg, Michael
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics UHL. Linköping University, Center for Medical Image Science and Visualization, CMIV.
    Smedby, Örjan
    Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Diagnostics, Department of Radiology in Linköping. Linköping University, Center for Medical Image Science and Visualization, CMIV.
    Application of adaptive non-linear 2D and 3D postprocessing filters for reduced dose abdominal CT2012In: Acta Radiologica, ISSN 0284-1851, E-ISSN 1600-0455, Vol. 53, no 3, p. 335-342Article in journal (Refereed)
    Abstract [en]

    Background: Abdominal computed tomography (an is a frequently performed imaging procedure, resulting in considerable radiation doses to the patient population. Postprocessing filters are one of several dose reduction measures that might help to reduce radiation doses without loss of image quality. less thanbrgreater than less thanbrgreater thanPurpose: To assess and compare the effect of two- and three-dimensional (2D, 3D) non-linear adaptive filters on reduced dose abdominal CT images. less thanbrgreater than less thanbrgreater thanMaterial and Methods: Two baseline abdominal CT image series with a volume computer tomography dose index (CTDI (vol)) of 12 mGy and 6 mGy were acquired for 12 patients. Reduced dose images were postprocessed with 2D and 3D filters. Six radiologists performed blinded randomized, side-by-side image quality assessments. Objective noise was measured. Data were analyzed using visual grading regression and mixed linear models. less thanbrgreater than less thanbrgreater thanResults: All image quality criteria were rated as superior for 3D filtered images compared to reduced dose baseline and 2D filtered images (P andlt; 0.01). Standard dose images had better image quality than reduced dose 3D filtered images (P andlt; 0.01), but similar image noise. For patients with body mass index (BMI) andlt; 30 kg/m(2) however, 3D filtered images were rated significantly better than normal dose images for two image criteria (P andlt; 0.05), while no significant difference was found for the remaining three image criteria (P andgt; 0.05). There were no significant variations of objective noise between standard dose and 2D or 3D filtered images. less thanbrgreater than less thanbrgreater thanConclusion: The quality of 3D filtered reduced dose abdominal CT images is superior compared to reduced dose unfiltered and 2D filtered images. For patients with BMI andlt; 30 kg/m(2), 3D filtered images are comparable to standard dose images.

  • 17.
    Brandejsky, Vaclav
    et al.
    Linköping University, Department of Medicine and Health Sciences, Radiation Physics. Östergötlands Läns Landsting, Centre for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics UHL. Linköping University, Faculty of Health Sciences.
    Dahlqvist Leinhard, Olof
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medicine and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Lund, Eva
    Linköping University, Department of Medicine and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Lundberg, Peter
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medicine and Health Sciences, Radiation Physics. Linköping University, Department of Medicine and Health Sciences, Radiology. Östergötlands Läns Landsting, Centre for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics UHL. Östergötlands Läns Landsting, Centre for Diagnostics, Department of Radiology in Linköping. Linköping University, Faculty of Health Sciences.
    A novel method for RF coil magnetic field mapping2008Conference paper (Other academic)
  • 18.
    Brandejsky, Vaclav
    et al.
    Linköping University, Department of Medicine and Health Sciences, Radiation Physics. Östergötlands Läns Landsting, Centre for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics UHL. Linköping University, Faculty of Health Sciences.
    Dahlqvist Leinhard, Olof
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medicine and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Lund, Eva
    Linköping University, Department of Medicine and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Lundberg, Peter
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medicine and Health Sciences, Radiation Physics. Linköping University, Department of Medicine and Health Sciences, Radiology. Östergötlands Läns Landsting, Centre for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics UHL. Östergötlands Läns Landsting, Centre for Diagnostics, Department of Radiology in Linköping. Linköping University, Faculty of Health Sciences.
    New MR-scanner independent B1 field mapping technique2009Conference paper (Other academic)
  • 19.
    Brolin, Gustav
    et al.
    Department of Medical Radiation Physics, Lund University, Sweden.
    Granerus, Göran
    Linköping University, Department of Medical and Health Sciences, Clinical Physiology. Linköping University, Department of Medical and Health Sciences, Cardiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Clinical Physiology in Linköping.
    Olsson, Anna
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Edenbrandt, Lars
    Department of Clinical Sciences, Malmö, Lund University, Sweden.
    Ljungberg, Michael
    Department of Medical Radiation Physics, Lund University, Sweden.
    A new Method for Monte Carlo Simulations of Dynamic Scintillation Camera Imaging: 99mTc MAG3 Renography Studies2012Conference paper (Other academic)
  • 20.
    Brynolfsson, Patrik
    Linköping University, Department of Medicine and Health Sciences, Radiation Physics. Linköping University, Center for Medical Image Science and Visualization, CMIV.
    Using radial k-space sampling and temporal filters in MRI to improve temporal resolution2010Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In this master thesis methods for increasing temporal resolution when reconstructing radially sampled MRI data have been developed and evaluated. This has been done in two steps; first the order in which data is sampled in k-space has been optimized, and second; temporal filters have been developed in order to utilize the high sampling density in central regions of k-space as a result of the polar sampling geometry to increase temporal resolution while maintaining image quality.By properly designing the temporal filters the temporal resolution is increased by a factor 3–20 depending on other variables such as imageresolution and the size of the time varying areas in the image. The results are obtained from simulated raw data and subsequent reconstruction. The next step should be to acquire and reconstruct raw data to confirm the results.

  • 21.
    Carlsson Tedgren, Asa
    et al.
    Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics.
    Ahnesjö, Anders
    Uppsala University.
    Optimization of the computational efficiency of a 3D, collapsed cone dose calculation algorithm for brachytherapy.2008In: Medical physics (Lancaster), ISSN 0094-2405, Vol. 35, no 4, p. 1611-1618Article in journal (Refereed)
    Abstract [en]

    Brachytherapy dose calculations based on point kernel superposition using the collapsed cone method have been shown to accurately model the influence from finite dimensions of the patient and effects from heterogeneities including those of high atomic numbers. The collapsed cone method is for brachytherapy applications most effectively implemented through a successive-scattering approach, in which the dose from once and higher order of scattered photons is calculated separately and in successive scatter order. The calculation speed achievable is directly proportional to the number of directions used for point kernel discretization and to the number of voxels in the volume. In this work we investigate how to best divide the total number of directions between the two steps of successive-scattering dose calculations. Results show that the largest fraction of the total number of directions should be utilized in calculating the first-scatter dose. Also shown is how the number of directions required for keeping discretization artifacts at acceptably low levels decreases significantly in multiple-source configurations, as a result of the dose gradients being less steep than those around single sources. Investigating the number of kernel directions required to keep artifacts low enough within the high dose region of an implant (i.e., for dose levels above approximately 5%-10% of the mean central target dose) reveals similar figures for brachytherapy as for external beam applications, where collapsed cone superposition is clinically used. Also shown is that approximating point kernels with their isotropic average leads to small dose differences at low and intermediate energies, implying that the collapsed cone calculations can be done in a single operation common to all sources of the implant at these energies. The current findings show that collapsed cone calculations can be achieved for brachytherapy with the same efficiency as for external beams. This, combined with recent results on gains in efficiency through implementing the algorithm on graphical card parallel hardware indicates that dose can be calculated with account for heterogeneities and finite dimensions within a few seconds for large voxel arrays and is therefore of interest for practical application to treatment planning.

  • 22.
    Carlsson Tedgren, Åsa
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics.
    Dose calculation and Monte Carlo simulations beyond the TG43 formalism2007In: 9th Biennial ESTRO meeting on physics and radiation technology for clinical radiotherapy,2007, 2007, p. S33-S33Conference paper (Other academic)
    Abstract [en]

       

  • 23.
    Carlsson Tedgren, Åsa
    et al.
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics.
    Alm Carlsson, Gudrun
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics.
    Evaluation of collapsed cone dose calculation accuracy for multiple source implants2008In: World Congress of Brachytherapy,2008, 2008, p. 136-136Conference paper (Other academic)
    Abstract [en]

          

  • 24.
    Carlsson Tedgren, Åsa
    et al.
    Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics.
    Alm Carlsson, Gudrun
    Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics.
    Influence of phantom material and dimensions on experimental Ir-192 dosimetry2009In: MEDICAL PHYSICS, ISSN 0094-2405, Vol. 36, no 6, p. 2228-2235Article in journal (Refereed)
    Abstract [en]

    In treatment planning of brachytherapy, absorbed dose is calculated by superposing predetermined distributions of absorbed dose to water in water for the single source according to the irradiation pattern [i.e., placement of the source(s) or dwelling position(s)]. Single-source reference water data are derived from Monte Carlo (MC) simulations and/or experiments. For reasons of positional accuracy, experimental brachytherapy dosimetry is most often performed in plastic phantoms. This work investigates the water equivalence of phantoms made from polystyrene, PMMA, and solid water for Ir-192 dosimetry. The EGSnrc MC code is used to simulate radial absorbed dose distributions in cylindrical phantoms of dimensions ranging in size from diameter and height of 20 cm to diameter and height of 40 cm. Water equivalence prevails if the absorbed dose to water in the plastic phantom is the same as the absorbed dose to water in a water phantom at equal distances from the source. It is shown that water equivalence at a specified distance from the source depends not only on the size of the plastic phantom but also on the size of the water phantom used for comparison. Compared to equally sized water phantoms, phantoms of polystyrene are less water equivalent than phantoms of PMMA and solid water but compared to larger water phantoms they are the most water equivalent. Although phantom dimension is the most important single factor influencing the dose distributions around Ir-192 sources, the effect of material properties is non-negligible and becomes increasingly important as phantom dimensions increase. The importance of knowing the size of the water phantom whose data underlies treatment planning systems, when using such data as a reference in, e.g., detector evaluation studies, is discussed. To achieve the highest possible accuracy in experimental dosimetry, phantom-specific correction factors should be used.

  • 25.
    Carlsson Tedgren, Åsa
    et al.
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics.
    Alm Carlsson, Gudrun
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics.
    Specification of absorbed dose to water using model-based dose calculation algorithms for treatment planning in brachytherapy2013In: Physics in Medicine and Biology, ISSN 0031-9155, E-ISSN 1361-6560, Vol. 58, no 8, p. 2561-2579Article in journal (Refereed)
    Abstract [en]

    Model-based dose calculation algorithms (MBDCAs), recently introduced in treatment planning systems (TPS) for brachytherapy, calculate tissue absorbed doses. In the TPS framework, doses have hereto been reported as dose to water and water may still be preferred as a dose specification medium. Dose to tissue medium D-med then needs to be converted into dose to water in tissue D-w,D- med. Methods to calculate absorbed dose to differently sized water compartments/cavities inside tissue, infinitesimal (used for definition of absorbed dose), small, large or intermediate, are reviewed. Burlin theory is applied to estimate photon energies at which cavity sizes in the range 1 nm-10 mm can be considered small or large. Photon and electron energy spectra are calculated at 1 cm distance from the central axis in cylindrical phantoms of bone, muscle and adipose tissue for 20, 50, 300 keV photons and photons from I-125, Yb-169 and Ir-192 sources; ratios of mass-collision-stopping powers and mass energy absorption coefficients are calculated as applicable to convert D-med into D-w,D- med for small and large cavities. Results show that 1-10 nm sized cavities are small at all investigated photon energies; 100 mu m cavities are large only at photon energies andlt;20 keV. A choice of an appropriate conversion coefficient D-w,D- med/D-med is discussed in terms of the cavity size in relation to the size of important cellular targets. Free radicals from DNA bound water of nanometre dimensions contribute to DNA damage and cell killing and may be the most important water compartment in cells implying use of ratios of mass -collision-stopping powers for converting D-med into D-w,D- med.

  • 26.
    Carlsson Tedgren, Åsa
    et al.
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics.
    Bengtsson, Emil
    Karolinska University Hospital.
    Hedtjärn, Håkan
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Health Sciences, Radiation Physics .
    Johansson, Asa
    Karolinska University Hospital.
    Karlsson, Leif
    Örebro University Hospital.
    Lamm, Inger-Lena
    Lund University Hospital.
    Lundell, Marie
    Karolinska University Hospital.
    Mejaddem, Younes
    Karolinska University Hospital.
    Munck af Rosenschold, Per
    Lund University Hospital.
    Nilsson, Josef
    Karolinska University Hospital.
    Wieslander, Elinore
    Lund University Hospital.
    Wolke, Jeanette
    Karolinska University Hospital.
    Experience from long-term monitoring of RAKR ratios in Ir-192 brachytherapy2008In: Radiotherapy and Oncology, ISSN 0167-8140, E-ISSN 1879-0887, Vol. 89, no 2, p. 217-221Article in journal (Refereed)
    Abstract [en]

    Background: Ratios of values of brachytherapy source strengths, as measured by hospitals and vendors, comprise constant differences as, e.g., systematic errors in ion chamber calibration factors and measurement setup. Such ratios therefore have the potential to reveal the systematic changes in routines or calibration services at either the hospital or the vendor laboratory, which could otherwise be hidden by the uncertainty in the source strength values.

    Methods: The RAKR of each new source in 13 afterloading units at five hospitals were measured by well-type ion chambers and compared to values for the same source stated on vendor certificates.

    Results: Differences from unity in the ratios of RAKR values determined by hospitals and vendors are most often small and stable around their mean values to within +/- 11.5%. Larger deviations are rare but occur. A decreasing ratio, seen at two hospitals for the same source, was useful in detecting an erroneous pressure gauge at the vendors site.

    Conclusions: Establishing a mean ratio of RAKR values, as measured at the hospital and supplied on the vendor certificate, and monitoring this as a function of time are an easy way for the early detection of problems with equipment or routines at either the hospital or the vendor site.

  • 27.
    Carlsson Tedgren, Åsa
    et al.
    Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics.
    de Luelmo, Sandro
    Swedish Radiation Safety Authority.
    Grindborg, Jan-Erik
    Swedish Radiation Safety Authority.
    Characterization of a Co-60 unit at a secondary standard dosimetry laboratory: Monte Carlo simulations compared to measurements and results from the literature2010In: Medical physics (Lancaster), ISSN 0094-2405, Vol. 37, no 6, p. 2777-2786Article in journal (Refereed)
    Abstract [en]

    Purpose: To compare a Monte Carlo (MC) characterization of a Co-60 unit at the Swedish Secondary Standard Dosimetry Laboratory (SSDL) with the results of both measurements and literature with the aims of (1) resolving a change in the ratio of air-kerma free in air K-air and absorbed dose to water D-w in a water phantom noted experimentally after a source exchange in the laboratory and (2) reviewing results from the literature on similar MC simulations. Although their use in radiotherapy is decreasing, the characteristics of Co-60 beams are of interest since Co-60 beams are utilized in calibrating ionization chambers for the absolute dosimetry of radiotherapy beams and as reference radiation quality in evaluating the energy dependence of radiation detectors and in studies on radiobiological effectiveness. Methods: The BEAMnrc MC code was used with a detailed geometrical model of the treatment head and two models of the Co-60 source representing the sources used before and after source exchange, respectively. The active diameters of the Co-60 sources were 1.5 cm in pellet form and 2.0 cm in sintered form. Measurements were performed on the actual unit at the Swedish SSDL. Results: Agreement was obtained between the MC and the measured results within the estimated uncertainties for beam profiles, water depth-dose curve, relative air-kerma output factors, and for the ratios of K-air/D-w before and after source exchange. The on-axis energy distribution of the photon fluence free in air for the unit loaded with its present (1.5 cm in diameter) source agreed closely with the results from the literature in which a source of the same make and active diameter, inside a different treatment head, was simulated. The spectrum for the larger (2.0 cm in diameter) source was in close agreement with another published spectrum, also modeling a Co-60 source with an active diameter of 2.0 cm inside a different treatment head. Conclusions: The reduction in the value of K-air/D-w following source exchange was explained by the spectral differences between the two sources that were larger in the free in-air geometry used for K-air calibrations than at 5 g/cm(2) depth in the water phantom used for D-w calibrations. Literature review revealed differences between published in-air Co-60 spectra derived for sources of different active diameters, and investigators in need of an accurately determined Co-60 in-air spectrum should be aware of differences due to source active diameter.

  • 28.
    Carlsson Tedgren, Åsa
    et al.
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics UHL.
    Elia, Rouba
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Hedtjärn, Håkan
    Östergötlands Läns Landsting, Centre for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics UHL.
    Olsson, Sara
    Östergötlands Läns Landsting, Centre for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics UHL.
    Alm Carlsson, Gudrun
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics UHL.
    Determination of absorbed dose to water around a clinical HDR 192-Ir source using LiF:Mg,Ti TLDs demonstrates an LET dependence of detector response2012In: Medical physics (Lancaster), ISSN 0094-2405, Vol. 39, no 2, p. 1133-1140Article in journal (Refereed)
    Abstract [en]

    Purpose: Experimental radiation dosimetry with thermoluminescent dosimeters (TLDs), calibrated in a (60)Co or megavoltage (MV) photon beam, is recommended by AAPM TG-43U1for verification of Monte Carlo calculated absorbed doses around brachytherapy sources. However, it has been shown by Carlsson Tedgren et al. [Med. Phys. 38, 5539-5550 (2011)] that for TLDs of LiF:Mg,Ti, detector response was 4% higher in a (137)Cs beam than in a (60)Co one. The aim of this work was to investigate if similar over-response exists when measuring absorbed dose to water around (192)Ir sources, using LiF:Mg,Ti dosimeters calibrated in a 6 MV photon beam.Methods: LiF dosimeters were calibrated to measure absorbed dose to water in a 6 MV photon beam and used to measure absorbed dose to water at distances of 3, 5, and 7 cm from a clinical high dose rate (HDR) (192)Ir source in a polymethylmethacrylate (PMMA) phantom. Measured values were compared to values of absorbed dose to water calculated using a treatment planning system (TPS) including corrections for the difference in energy absorption properties between calibration quality and the quality in the users' (192)Ir beam and for the use of a PMMA phantom instead of the water phantom underlying dose calculations in the TPS.Results: Measured absorbed doses to water around the (192)Ir source were overestimated by 5% compared to those calculated by the TPS. Corresponding absorbed doses to water measured in a previous work with lithium formate electron paramagnetic resonance (EPR) dosimeters by Antonovic et al. [Med. Phys. 36, 2236-2247 (2009)], using the same irradiation setup and calibration procedure as in this work, were 2% lower than those calculated by the TPS. The results obtained in the measurements in this work and those obtained using the EPR lithium formate dosimeters were, within the expanded (k = 2) uncertainty, in agreement with the values derived by the TPS. The discrepancy between the results using LiF:Mg,Ti TLDs and the EPR lithium formate dosimeters was, however, statistically significant and in agreement with the difference in relative detector responses found for the two detector systems by Carlsson Tedgren et al. [Med. Phys. 38, 5539-5550 (2011)] and by Adolfsson et al. [Med. Phys. 37, 4946-4959 (2010)].Conclusions: When calibrated in (60)Co or MV photon beams, correction for the linear energy transfer (LET) dependence of LiF:Mg,Ti detector response will be needed as to measure absorbed doses to water in a (192)Ir beam with highest accuracy. Such corrections will depend on the manufacturing process (MTS-N Poland or Harshaw TLD-100) and details of the annealing and read-out schemes used.

  • 29.
    Carlsson Tedgren, Åsa
    et al.
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics.
    Grindborg, Jan-Erik
    Stockholm.
    Audit on source strength determination for HDR and PDR 192Ir brachytherapy in Sweden2008In: Radiotherapy and Oncology, ISSN 0167-8140, E-ISSN 1879-0887, Vol. 86, no 1, p. 126-130Article in journal (Refereed)
    Abstract [en]

    Background and purpose: To investigate the status of source strength determination in terms of reference air kerma rate (RAKR) for HDR and PDR 192Ir brachytherapy in Sweden. Materials and methods: RAKR was determined in each of the 14 Swedish afterloaders, using calibrated equipment from the Swedish Secondary Standard Dosimetry Laboratory. Results: Values of RAKR from the external audit, the hospitals and vendors agreed within the uncertainty limits guaranteed by the vendors. Conclusions: The accuracy in RAKR determination has increased over the last years as a result of increased availability of interpolation standards for HDR 192Ir and the increased use of robust well-type ion chambers designed for brachytherapy. It is recommended to establish a ratio between the RAKR value from own measurements at the hospital and that of the vendor since such a ratio embeds constant systematic differences due to e.g. varying traceability and therefore has the potential of being less uncertain than the RAKR alone. Traceability to primary standards for HDR 192Ir sources will in the future significantly decrease the uncertainty in RAKR of 192Ir brachytherapy. © 2007 Elsevier Ireland Ltd. All rights reserved.

  • 30.
    Carlsson Tedgren, Åsa
    et al.
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics.
    Grindborg, J-E
    Stockholm.
    192-Ir source strength dosimetry audit in Sweden2007In: 9th Biennial ESTRO meeting on physics and radiation technology for clinical radiotherapy,2007, 2007, p. S143-S143Conference paper (Other academic)
    Abstract [en]

    Posters Brachytherapy, publicerad i Radiotherapy and Oncology.

  • 31.
    Carlsson Tedgren, Åsa
    et al.
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics UHL.
    Hedman, Angelica
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics UHL.
    Grindborg, Jan-Erik
    Swedish Radiation Safety Authority.
    Alm Carlsson, Gudrun
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics UHL. Linköping University, Center for Medical Image Science and Visualization, CMIV.
    Response of LiF:Mg,Ti thermoluminescent dosimeters at photon energies relevant to the dosimetry of brachytherapy (andlt; 1 MeV)2011In: Medical physics (Lancaster), ISSN 0094-2405, Vol. 38, no 10, p. 5539-5550Article in journal (Refereed)
    Abstract [en]

    Purpose: High energy photon beams are used in calibrating dosimeters for use in brachytherapy since absorbed dose to water can be determined accurately and with traceability to primary standards in such beams, using calibrated ion chambers and standard dosimetry protocols. For use in brachytherapy, beam quality correction factors are needed, which include corrections for differences in mass energy absorption properties between water and detector as well as variations in detector response (intrinsic efficiency) with radiation quality, caused by variations in the density of ionization (linear energy transfer (LET) -distributions) along the secondary electron tracks. The aim of this work was to investigate experimentally the detector response of LiF:Mg, Ti thermoluminescent dosimeters (TLD) for photon energies below 1 MeV relative to (60)Co and to address discrepancies between the results found in recent publications of detector response. less thanbrgreater than less thanbrgreater thanMethods: LiF:Mg,Ti dosimeters of formulation MTS-N Poland were irradiated to known values of air kerma free-in-air in x-ray beams at tube voltages 25-250 kV, in (137)Cs- and (60)Co-beams at the Swedish Secondary Standards Dosimetry Laboratory. Conversions from air kerma free-in-air into values of mean absorbed dose in the dosimeters in the actual irradiation geometries were made using EGSnrc Monte Carlo simulations. X-ray energy spectra were measured or calculated for the actual beams. Detector response relative to that for (60)Co was determined at each beam quality. less thanbrgreater than less thanbrgreater thanResults: An increase in relative response was seen for all beam qualities ranging from 8% at tube voltage 25 kV (effective energy 13 keV) to 3%-4% at 250 kV (122 keV effective energy) and (137)Cs with a minimum at 80 keV effective energy (tube voltage 180 kV). The variation with effective energy was similar to that reported by Davis [Radiat. Prot. Dosim. 106, 33-43 (2003)] with our values being systematically lower by 2%-4%. Compared to the results by Nunn [Med. Phys. 35, 1861-1869 (2008)], the relative detector response as a function of effective energy differed in both shape and magnitude. This could be explained by the higher maximum read-out temperature (350 degrees C) used by Nunn [Med. Phys. 35, 1861-1869 (2008)], allowing light emitted from high-temperature peaks with a strong LET dependence to be registered. Use of TLD-100 by Davis [Radiat. Prot. Dosim. 106, 33-43 (2003)] with a stronger super-linear dose response compared to MTS-N was identified as causing the lower relative detector response in this work. less thanbrgreater than less thanbrgreater thanConclusions: Both careful dosimetry and strict protocols for handling the TLDs are required to reach solid experimental data on relative detector response. This work confirms older findings that an over-response relative to (60)Co exists for photon energies below 200-300 keV. Comparison with the results from the literature indicates that using similar protocols for annealing and read-out, dosimeters of different makes (TLD-100, MTS-N) differ in relative detector response. Though universality of the results has not been proven and further investigation is needed, it is anticipated that with the use of strict protocols for annealing and read-out, it will be possible to determine correction factors that can be used to reduce uncertainties in dose measurements around brachytherapy sources at photon energies where primary standards for absorbed dose to water are not available.

  • 32.
    Dahlqvist Leinhard, Olof
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Quantitative magnetic resonance in diffuse liver and neurological disease2008Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Magnetic resonance (MR) has become one of the most important diagnostic tools in modern medicine. It provides superior soft tissue contrast compared to other imaging modalities, it is extremely flexible as it can be used to image all parts of the body, and it is considered to be safe for patients.

    Today almost all MR is performed in a non-quantitative manner, only by comparing neighbouring tissue in the search for pathology. It is possible to quantify the MR-signals to its physical entities, but time consuming and complicated calibration procedures have prevented this in clinical routine.

    In this work two different applications of quantitative MR-spectroscopy in diffuse liver and neurological disease, and a new rapid method for simultaneous quantification of proton density, T1 relaxation and T2* relaxation in MR-imaging are presented.

    In Paper I, absolutely quantified phosphorus MR-spectroscopy was tested as a predictive tool in order to determine the degree of fibrosis on patients with diffuse liver disease. One group with steatosis and none to moderate inflammation (n=13), one group with severe fibrosis or cirrhosis (n=16), and one group of healthy volunteers (n=13) were included in the study.

    Lower concentrations of PDE (p = 0.025), and a higher metabolic charge (AC) [42] (p < 0.001) were found in the cirrhosis group. A sensitivity and specificity of 81% and 69% respectively, were found for the discrimination between mild and advanced fibrosis using PDE concentrations, and 93% and 54% using AC. The results suggest PDE as a marker of liver fibrosis and AC as a potential clinically useful parameter in discriminating mild from advanced fibrosis.

    In Paper II proton MR-spectroscopy was used to investigate if there were differences in the concentrations of the observable metabolites in normal appearing white matter in patients with clinically definite multiple sclerosis (MS), and with normal MR-images compared to healthy volunteers. This 'MRI-negative' group consisted of fourteen patients which were compared with fourteen healthy controls. Absolutely quantified proton MR-spectra were acquired from four different voxels in NAWM.

    Significant differences in absolute metabolite concentrations were observed between the two groups. The MS-patients had lower total N-acetyl compounds (tNA) (p=0.002) compared to the healthy controls and lower concentration of choline-containing compounds (Cho) compared to the healthy controls (p<0.001). EDSS showed a slightly positive correlation to myolns concentrations (0.14mM/EDSS,r2 = 0.06) and a slightly negative correlation to tNA concentrations (-0.41 mM/EDSS,r2 = 0.22). The finding of lower Cho concentrations has not been reported previously and was unexpected.

    In Paper III a new rapid imaging method was presented for determination of proton density, B1, T2* relaxation and T1 relaxation. The method was based on a modified Look-Locker pulse sequence with two main differences. (1) The exchange of the inversion pulse in the Lock-Looker sequence to a saturation pulse in order to enable detection of the B1 field, and (2) the introduction of a multi-echo read-out to enable the detection of T2*. The signal intensity was then scaled to proton density using the estimated B1, T1, and T2* value.

    The method was validated in vitro, using phantoms filled with solution of different T1 and T2* water relaxation values, and by comparing the results of the measurements to reference metcyods. In vivo the method was compared with literature values.

    The validation showed that the method was highly accurate, both in vitro and in vivo, and that this method enabled quantitative imaging of MR-parameters within a clinically feasible examination time. Potential applications of the method are, among a great range of possibilities, to rapidly provide all the necessary quantification parameters in MR-spectroscopy, and to simultaneously provide fast quantitative diagnostic imaging.

    List of papers
    1. Separation of advanced from mild fibrosis in diffuse liver disease using 31P magnetic resonance spectroscopy
    Open this publication in new window or tab >>Separation of advanced from mild fibrosis in diffuse liver disease using 31P magnetic resonance spectroscopy
    Show others...
    2008 (English)In: European Journal of Radiology, ISSN 0720-048X, E-ISSN 1872-7727, Vol. 66, no 2, p. 313-320Article in journal (Refereed) Published
    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.

    Place, publisher, year, edition, pages
    Elsevier, 2008
    Keywords
    Absolute quantification; Phosphorus; MRS; Steatosis; In vivo
    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-43125 (URN)10.1016/j.ejrad.2007.06.004 (DOI)000256140900026 ()17646074 (PubMedID)71944 (Local ID)71944 (Archive number)71944 (OAI)
    Projects
    NILB
    Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2017-12-13Bibliographically approved
    2. Low Choline Concentrations in Normal-Appearing White Matter of Patients with Multiple Sclerosis and Normal MR Imaging Brain Scans
    Open this publication in new window or tab >>Low Choline Concentrations in Normal-Appearing White Matter of Patients with Multiple Sclerosis and Normal MR Imaging Brain Scans
    Show others...
    2007 (English)In: American Journal of Neuroradiology, ISSN 0195-6108, E-ISSN 1936-959X, Vol. 28, no 7, p. 1306-1312Article in journal (Refereed) Published
    Abstract [en]

    BACKGROUND AND PURPOSE: Spectroscopic studies (1H-MR spectroscopy) of normal-appearing white matter (NAWM) in patients with multiple sclerosis (MS) with MR imaging brain lesions have already been performed, but our intention was to investigate NAWM in MS patients who lack brain lesions to elucidate whether the same pathologic changes could be identified.

    MATERIALS AND METHODS: We checked 350 medical files of patients with MS who are registered in our institution. Fourteen patients (11 women and 3 men; mean age, 48.6 years; handicap score, Expanded Disability Status Scale [EDSS] 2.9; range, 1–6.5) with clinically definite MS and a normal MR imaging of the brain were included. 1H-MR spectroscopy was performed in 4 voxels (size approximately 17 × 17 × 17 mm3) using absolute quantification of metabolite concentrations. Fourteen healthy control subjects (11 women and 3 men; mean age, 43.3 years) were analyzed in the same way.

    RESULTS: Significant differences in absolute metabolite concentrations were observed, with the patients with MS showing a lower total concentration of N-acetyl compounds (tNA), including N-acetylaspartate and N-acetyl aspartylglutamate (13.5 mmol/L versus 14.6 mmol/L; P = .002) compared with the healthy control subjects. Unexpectedly, patients with MS presented significantly lower choline-containing compounds (Cho) compared with healthy control subjects (2.2 mmol/L versus 2.4 mmol/L; P < .001). The EDSS showed a positive correlation to myo-inositol concentrations (0.14 mmol/L per EDSS; r2 = 0.06) and a negative correlation to tNA concentrations (−0.41 mmol/L per EDSS; r2 = 0.22).

    CONCLUSION: The unexpected finding of lower Cho concentrations has not been reported previously. We suggest that patients with MS who lack lesions in the brain constitute a separate entity and may have increased protective or healing abilities.

    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-39360 (URN)10.3174/ajnr.A0580 (DOI)000249278700021 ()47991 (Local ID)47991 (Archive number)47991 (OAI)
    Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2018-03-20
    3. Novel method for rapid, simultaneous T1, T*2, and proton density quantification
    Open this publication in new window or tab >>Novel method for rapid, simultaneous T1, T*2, and proton density quantification
    2007 (English)In: Magnetic Resonance in Medicine, ISSN 0740-3194, E-ISSN 1522-2594, Vol. 57, no 3, p. 528-537Article in journal (Refereed) Published
    Abstract [en]

    An imaging method called “quantification of relaxation times and proton density by twin-echo saturation-recovery turbo-field echo” (QRAPTEST) is presented as a means of quickly determining the longitudinal T1 and transverse T relaxation time and proton density (PD) within a single sequence. The method also includes an estimation of the B1 field inhomogeneity. High-resolution images covering large volumes can be achieved within clinically acceptable times of 5–10 min. The range of accuracy for determining T1, T, and PD values is flexible and can be optimized relative to any anticipated values. We validated the experimental results against existing methods, and provide a clinical example in which quantification of the whole brain using 1.5 mm3 voxels was achieved in less than 8 min.

    Keywords
    Proton density mapping, Quantitative mri, Rapid quantification, T1 mapping, T2* mapping
    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-49979 (URN)10.1002/mrm.21165 (DOI)000244657200010 ()
    Available from: 2009-10-11 Created: 2009-10-11 Last updated: 2017-12-12
  • 33.
    Dahlqvist Leinhard, Olof
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Quantitative Magnetic Resonance in Diffuse Neurological and Liver Disease2010Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Introduction: Magnetic resonance (MR) imaging is one of the most important diagnostic tools in modern medicine. Compared to other imaging modalities, it provides superior soft tissue contrast of all parts of the body and it is considered to be safe for patients. Today almost all MR is performed in a nonquantitative manner, only comparing neighboring tissue in the search for pathology. It is possible to quantify MR-signals and relate them to their physical entities, but time consuming and complicated calibration procedures have prevented this being used in a practical manner for clinical routines. The aim of this work is to develop and improve quantification methods in MRspectroscopy (MRS) and MR-imaging (MRI). The techniques are intended to be applied to diffuse diseases, where conventional imaging methods are unable to perform accurate staging or to reveal metabolic changes associated with disease development.

    Methods: Proton (1H) MRS was used to characterize the white matter in the brain of multiple sclerosis (MS) patients. Phosphorus (31P) MRS was used to evaluate the energy metabolism in patients with diffuse liver disease. A new quantitative MRI (qMRI) method was invented for accurate, rapid and simultaneous quantification of B1, T1, T2, and proton density. A method for automatic assessment of visceral adipose tissue volume based on an in- and out-ofphase imaging protocol was developed. Finally, a method for quantification of the hepatobiliary uptake of liver specific T1 enhancing contrast agents was demonstrated on healthy subjects.

    Results: The 1H MRS investigations of white matter in MS-patients revealed a significant correlation between tissue concentrations of Glutamate and Creatine on the one hand and the disease progression rate on the other, as measured using the MSSS. High accuracy, both in vitro and in vivo, of the measured MR-parameters from the qMRI method was observed. 31P MRS showed lower concentrations of phosphodiesters, and a higher metabolic charge in patients with cirrhosis, compared to patients with mild fibrosis and to controls. The adipose tissue quantification method agreed with estimates obtained using manual segmentation, and enabled measurements which were insensitive to partial volume effects. The hepatobiliary uptake of Gd-EOB-DTPA and Gd-BOPTA was significantly correlated in healthy subjects.

    Conclusion: In this work, new methods for accurate quantification of MR parameters in diffuse diseases in the liver and the brain were demonstrated. Several applications were shown where quantitative MR improves the interpretation of observed signal changes in MRI and MRS in relation to underlying differences in physiology and pathophysiology.

    List of papers
    1. Low Choline Concentrations in Normal-Appearing White Matter of Patients with Multiple Sclerosis and Normal MR Imaging Brain Scans
    Open this publication in new window or tab >>Low Choline Concentrations in Normal-Appearing White Matter of Patients with Multiple Sclerosis and Normal MR Imaging Brain Scans
    Show others...
    2007 (English)In: American Journal of Neuroradiology, ISSN 0195-6108, E-ISSN 1936-959X, Vol. 28, no 7, p. 1306-1312Article in journal (Refereed) Published
    Abstract [en]

    BACKGROUND AND PURPOSE: Spectroscopic studies (1H-MR spectroscopy) of normal-appearing white matter (NAWM) in patients with multiple sclerosis (MS) with MR imaging brain lesions have already been performed, but our intention was to investigate NAWM in MS patients who lack brain lesions to elucidate whether the same pathologic changes could be identified.

    MATERIALS AND METHODS: We checked 350 medical files of patients with MS who are registered in our institution. Fourteen patients (11 women and 3 men; mean age, 48.6 years; handicap score, Expanded Disability Status Scale [EDSS] 2.9; range, 1–6.5) with clinically definite MS and a normal MR imaging of the brain were included. 1H-MR spectroscopy was performed in 4 voxels (size approximately 17 × 17 × 17 mm3) using absolute quantification of metabolite concentrations. Fourteen healthy control subjects (11 women and 3 men; mean age, 43.3 years) were analyzed in the same way.

    RESULTS: Significant differences in absolute metabolite concentrations were observed, with the patients with MS showing a lower total concentration of N-acetyl compounds (tNA), including N-acetylaspartate and N-acetyl aspartylglutamate (13.5 mmol/L versus 14.6 mmol/L; P = .002) compared with the healthy control subjects. Unexpectedly, patients with MS presented significantly lower choline-containing compounds (Cho) compared with healthy control subjects (2.2 mmol/L versus 2.4 mmol/L; P < .001). The EDSS showed a positive correlation to myo-inositol concentrations (0.14 mmol/L per EDSS; r2 = 0.06) and a negative correlation to tNA concentrations (−0.41 mmol/L per EDSS; r2 = 0.22).

    CONCLUSION: The unexpected finding of lower Cho concentrations has not been reported previously. We suggest that patients with MS who lack lesions in the brain constitute a separate entity and may have increased protective or healing abilities.

    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-39360 (URN)10.3174/ajnr.A0580 (DOI)000249278700021 ()47991 (Local ID)47991 (Archive number)47991 (OAI)
    Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2018-03-20
    2. Rapid magnetic resonance quantification on the brain: Optimization for clinical usage
    Open this publication in new window or tab >>Rapid magnetic resonance quantification on the brain: Optimization for clinical usage
    2008 (English)In: Magnetic Resonance in Medicine, ISSN 0740-3194, E-ISSN 1522-2594, Vol. 60, no 2, p. 320-329Article in journal (Refereed) Published
    Abstract [en]

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

    Keywords
    quantitatie MRI, T1 mapping, T2mapping, PD mapping, B1 mapping, synthetic MRI, neurodegenerative disease
    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-42804 (URN)10.1002/mrm.21635 (DOI)000258105800011 ()68904 (Local ID)68904 (Archive number)68904 (OAI)
    Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2017-12-13Bibliographically approved
    3. Is Increased Normal White Matter Glutamate Concentration a Precursor of Gliosis and Disease Progression in Multiple Sclerosis?
    Open this publication in new window or tab >>Is Increased Normal White Matter Glutamate Concentration a Precursor of Gliosis and Disease Progression in Multiple Sclerosis?
    Show others...
    (English)Manuscript (preprint) (Other academic)
    Abstract [en]

    Background: The multiple sclerosis (MS) severity scale (MSSS) is a new scoring procedure to clinically characterize the rate of disease progression in MS, rather than the disability of the patient. The latter is often characterized using the expanded disability status score (EDSS). The progress rate of the disease, magnetic resonance imaging (MRI)-based measures of ‘black hole lesions’, and atrophy have all been shown to be predicted well by MSSS. In this study we investigated possible relationships between brain metabolite concentrations, measured using proton (1H) magnetic resonance spectroscopy (MRS), and MSSS.

    Purpose: Our aims were to quantitatively investigate the metabolite concentrations in normal appearing white matter (NAWM) in MS-patients, and also to investigate possible correlations between disease subtype, EDSS and MSSS and metabolite concentrations. To minimize the interference from lesion contamination in the MRS measurement, a refined novel analysis procedure had to be developed in order to correct for partial volume effects in tissues near plaques.

    Materials and Methods: Forty eight patients with Clinically Definite MS (CDMS), and 18 normal control subjects (NC) were included retrospectively from several MRS studies. T1, T2, and proton density MRI, and four white matter 1H MRS single voxel PRESS (Point-REsolved SpectroScopy) spectra were acquired in each subject using echo time 35 ms and repetition time 6000 ms on a 1.5 T MR-scanner. A total of 108 examinations were acquired from patients and 18 from NC. Absolutely quantified NAWM metabolite concentrations were determined using a mixed linear model (MLM) analysis that included the degree of T2 lesion contamination in each voxel. The T2 lesion contamination of the MRS voxels was also used as an estimate of ‘lesion load’ at each exam. The corrected metabolite concentrations were then correlated with clinical measures of the patients’ status, including EDSS and MSSS.

    Results: The axonal marker N-acetyl aspartate (NAA) did not correlate with either EDSS or MSSS. The glial cell markers creatine and myo-inositol correlated positively with EDSS. Creatine and glutamate correlated positively with MSSS. The ‘estimated lesion load’ correlated positively not only with EDSS, but also with the number of bouts since disease onset. Importantly, it did not correlate with MSSS.

    Conclusion: The most interesting findings were the unchanged concentrations of NAA, and the concomitant increase of creatine and myo-inositol during the course of disease progression in MSpatients. These not only indicated a constant axonal density, but also that a simultaneous development of gliosis occurred. These processes are most likely linked to demyelination, as well as development of white matter atrophy, a process in which the demyelinated volume is replaced by the surrounding tissue leading to a net loss of white matter. As a consequence of this process, axons in NAWM are probably damaged, which leads to a higher concentration of glia cells relative to the axonal volume. The positive correlation that was found between MSSS, and the glutamate and creatine concentrations in NAWM, in combination with a complete lack of correlation between lesion load and MSSS, suggests that altered glutamate metabolism, and subsequent demyelination and gliosis, is an important pathophysiological mechanism in MS.

    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-54726 (URN)
    Available from: 2010-04-07 Created: 2010-04-07 Last updated: 2014-10-02Bibliographically approved
    4. Separation of advanced from mild fibrosis in diffuse liver disease using 31P magnetic resonance spectroscopy
    Open this publication in new window or tab >>Separation of advanced from mild fibrosis in diffuse liver disease using 31P magnetic resonance spectroscopy
    Show others...
    2008 (English)In: European Journal of Radiology, ISSN 0720-048X, E-ISSN 1872-7727, Vol. 66, no 2, p. 313-320Article in journal (Refereed) Published
    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.

    Place, publisher, year, edition, pages
    Elsevier, 2008
    Keywords
    Absolute quantification; Phosphorus; MRS; Steatosis; In vivo
    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-43125 (URN)10.1016/j.ejrad.2007.06.004 (DOI)000256140900026 ()17646074 (PubMedID)71944 (Local ID)71944 (Archive number)71944 (OAI)
    Projects
    NILB
    Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2017-12-13Bibliographically approved
    5. Quantitative Abdominal Fat Estimation Using MRI
    Open this publication in new window or tab >>Quantitative Abdominal Fat Estimation Using MRI
    Show others...
    2008 (English)In: Proceedings - International Conference on Pattern Recognition, IEEE Computer Society, 2008, p. 1-4Conference paper, Published paper (Refereed)
    Abstract [en]

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

    Place, publisher, year, edition, pages
    IEEE Computer Society, 2008
    Series
    International Conference on Pattern Recognition, ISSN 1051-4651
    National Category
    Medical Laboratory and Measurements Technologies
    Identifiers
    urn:nbn:se:liu:diva-21108 (URN)10.1109/ICPR.2008.4761764 (DOI)000264729001041 ()978-1-4244-2174-9 (ISBN)978-1-4244-2175-6 (ISBN)
    Conference
    19th International Conference on Pattern Recognition, Tampa FL USA, 8-11 Dec. 2008
    Available from: 2009-09-29 Created: 2009-09-29 Last updated: 2018-09-11Bibliographically approved
    6. Quantifying differences in hepatic uptake of the liver specific contrast agents Gd-EOB-DTPA and Gd-BOPTA: a pilot study
    Open this publication in new window or tab >>Quantifying differences in hepatic uptake of the liver specific contrast agents Gd-EOB-DTPA and Gd-BOPTA: a pilot study
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    2012 (English)In: European Radiology, ISSN 0938-7994, E-ISSN 1432-1084, Vol. 22, no 3, p. 642-653Article in journal (Refereed) Published
    Abstract [en]

    Objectives   To develop and evaluate a procedure for quantifying the hepatocyte-specific uptake of Gd-BOPTA and Gd-EOB-DTPA using dynamic contrast-enhanced (DCE) MRI. Methods   Ten healthy volunteers were prospectively recruited and 21 patients with suspected hepatobiliary disease were retrospectively evaluated. All subjects were examined with DCE-MRI using 0.025 mmol/kg of Gd-EOB-DTPA. The healthy volunteers underwent an additional examination using 0.05 mmol/kg of Gd-BOPTA. The signal intensities (SI) of liver and spleen parenchyma were obtained from unenhanced and enhanced acquisitions. Using pharmacokinetic models of the liver and spleen, and an SI rescaling procedure, a hepatic uptake rate, K Hep, estimate was derived. The K Hep values for Gd-EOB-DTPA were then studied in relation to those for Gd-BOPTA and to a clinical classification of the patient’s hepatobiliary dysfunction. Results   K Hep estimated using Gd-EOB-DTPA showed a significant Pearson correlation with K Hep estimated using Gd-BOPTA (r = 0.64; P < 0.05) in healthy subjects. Patients with impaired hepatobiliary function had significantly lower K Hep than patients with normal hepatobiliary function (K Hep = 0.09 ± 0.05 min-1 versus K Hep = 0.24 ± 0.10 min−1; P < 0.01). Conclusions   A new procedure for quantifying the hepatocyte-specific uptake of T 1-enhancing contrast agent was demonstrated and used to show that impaired hepatobiliary function severely influences the hepatic uptake of Gd-EOB-DTPA. Key Points   • The liver uptake of contrast agents may be measured with standard clinical MRI.Calculation of liver contrast agent uptake is improved by considering splenic uptake.Liver function affects the uptake of the liver-specific contrast agent Gd-EOB-DTPA.Hepatic uptake of two contrast agents (Gd-EOB-DTPA, Gd-BOPTA) is correlated in healthy individuals.This method can be useful for determining liver function, e.g. before hepatic surgery

    Place, publisher, year, edition, pages
    Springer Berlin/Heidelberg, 2012
    Keywords
    Gadolinium ethoxybenzyl diethylenetriaminepentaacetic acid – Gadobenate Dimeglumine – Dynamic contrast-enhanced MRI – Pharmacokinetics – Liver
    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-73624 (URN)10.1007/s00330-011-2302-4 (DOI)000299768000018 ()21984449 (PubMedID)
    Funder
    Swedish Research Council, VR/M 2007-2884Medical Research Council of Southeast Sweden (FORSS), 12621Linköpings universitet
    Note

    The previous status of this article was Manuscript and the working titles was Liver Specific Gd-EOB-DTPA vs. Gd-BOPTA Uptake in Healthy Subjects: A Novel and Quantitative MRI Analysis of Hepatic Uptake and Vascular Enhancement and Hepatic Uptake of Gd-EOB-DTPA in Patients with Varying Degree of Hepatobiliary Disease.

    Available from: 2012-01-10 Created: 2012-01-10 Last updated: 2017-12-08
  • 34.
    Dahlqvist Leinhard, Olof
    et al.
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Cohen, L
    Lund, Eva
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Lundberg, Peter
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Department of Medical and Health Sciences, Radiology. Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping. Linköping University, Faculty of Health Sciences.
    Absolute quantification of 31P muscle MRS using B1-field mapping2005Conference paper (Other academic)
  • 35.
    Dahlqvist Leinhard, Olof
    et al.
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Health Sciences. Linköping University, Center for Medical Image Science and Visualization, CMIV.
    Dahlström, Nils
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Health Sciences, Radiology . Linköping University, Center for Medical Image Science and Visualization, CMIV.
    Brismar, T
    Sandström, Per
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Clinical and Experimental Medicine, Surgery . Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Surgery in Östergötland.
    Kihlberg, Johan
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Health Sciences. Linköping University, Center for Medical Image Science and Visualization, CMIV.
    Smedby, Örjan
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Medical Radiology. Östergötlands Läns Landsting, Centre for Medical Imaging, Department of Radiology UHL. Linköping University, Center for Medical Image Science and Visualization, CMIV.
    Lundberg, Peter
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Linköping University, Department of Medicine and Health Sciences, Radiology . Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics. Östergötlands Läns Landsting, Centre for Medical Imaging, Department of Radiology in Linköping.
    A liver function test based on measurement of liver-specific contrast agent uptake2008In: Proceedings 16th Scientific meeting, ISMRM,2008, 2008Conference paper (Other academic)
    Abstract [en]

      

  • 36.
    Dahlqvist Leinhard, Olof
    et al.
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Dahlström, Nils
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Kihlberg, Johan
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Sandström, Per
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Clinical and Experimental Medicine, Surgery.
    Brismar, Torkel
    Department of Clinical Science, Intervention and Technology at Karolinska Institutet, Division of Medical Imaging and Technology, Karolinska University Hospital in Huddinge, Stockholm, Sweden.
    Smedby, Örjan
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Lundberg, Peter
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Quantifying differences in hepatic uptake of the liver specific contrast agents Gd-EOB-DTPA and Gd-BOPTA: a pilot study2012In: European Radiology, ISSN 0938-7994, E-ISSN 1432-1084, Vol. 22, no 3, p. 642-653Article in journal (Refereed)
    Abstract [en]

    Objectives   To develop and evaluate a procedure for quantifying the hepatocyte-specific uptake of Gd-BOPTA and Gd-EOB-DTPA using dynamic contrast-enhanced (DCE) MRI. Methods   Ten healthy volunteers were prospectively recruited and 21 patients with suspected hepatobiliary disease were retrospectively evaluated. All subjects were examined with DCE-MRI using 0.025 mmol/kg of Gd-EOB-DTPA. The healthy volunteers underwent an additional examination using 0.05 mmol/kg of Gd-BOPTA. The signal intensities (SI) of liver and spleen parenchyma were obtained from unenhanced and enhanced acquisitions. Using pharmacokinetic models of the liver and spleen, and an SI rescaling procedure, a hepatic uptake rate, K Hep, estimate was derived. The K Hep values for Gd-EOB-DTPA were then studied in relation to those for Gd-BOPTA and to a clinical classification of the patient’s hepatobiliary dysfunction. Results   K Hep estimated using Gd-EOB-DTPA showed a significant Pearson correlation with K Hep estimated using Gd-BOPTA (r = 0.64; P < 0.05) in healthy subjects. Patients with impaired hepatobiliary function had significantly lower K Hep than patients with normal hepatobiliary function (K Hep = 0.09 ± 0.05 min-1 versus K Hep = 0.24 ± 0.10 min−1; P < 0.01). Conclusions   A new procedure for quantifying the hepatocyte-specific uptake of T 1-enhancing contrast agent was demonstrated and used to show that impaired hepatobiliary function severely influences the hepatic uptake of Gd-EOB-DTPA. Key Points   • The liver uptake of contrast agents may be measured with standard clinical MRI.Calculation of liver contrast agent uptake is improved by considering splenic uptake.Liver function affects the uptake of the liver-specific contrast agent Gd-EOB-DTPA.Hepatic uptake of two contrast agents (Gd-EOB-DTPA, Gd-BOPTA) is correlated in healthy individuals.This method can be useful for determining liver function, e.g. before hepatic surgery

  • 37.
    Dahlqvist Leinhard, Olof
    et al.
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Dahlström, Nils
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiology. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping. Linköping University, Faculty of Health Sciences.
    Sandström, P
    Brismar, Torkel
    Karolinska institutet.
    Kihlberg, Johan
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiology. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping. Linköping University, Faculty of Health Sciences.
    Smedby, Örjan
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiology. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping. Linköping University, Faculty of Health Sciences.
    Lundberg, Peter
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Department of Medical and Health Sciences, Radiology. Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics. Linköping University, Faculty of Health Sciences.
    A liver function test based on measurement of liver specific contrast agent uptake2008Conference paper (Other academic)
  • 38.
    Dahlqvist Leinhard, Olof
    et al.
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medicine and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Dahlström, Nils
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medicine and Health Sciences, Radiology. Östergötlands Läns Landsting, Centre for Diagnostics, Department of Radiology in Linköping. Linköping University, Faculty of Health Sciences.
    Sandström, P
    Freij, Anna
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medicine and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Kihlberg, Johan
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medicine and Health Sciences, Radiology. Östergötlands Läns Landsting, Centre for Diagnostics, Department of Radiology in Linköping. Linköping University, Faculty of Health Sciences.
    Brismar, Torkel
    Karolinska institutet.
    Smedby, Örjan
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medicine and Health Sciences, Radiology. Östergötlands Läns Landsting, Centre for Diagnostics, Department of Radiology in Linköping. Linköping University, Faculty of Health Sciences.
    Lundberg, Peter
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medicine and Health Sciences, Radiation Physics. Linköping University, Department of Medicine and Health Sciences, Radiology. Östergötlands Läns Landsting, Centre for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics UHL. Östergötlands Läns Landsting, Centre for Diagnostics, Department of Radiology in Linköping. Linköping University, Faculty of Health Sciences.
    The hepatic uptake of Gd-EOB-DTPA is strongly affected by the hepatobiliary function2009Conference paper (Other academic)
  • 39.
    Dahlqvist Leinhard, Olof
    et al.
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medicine and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Dahlström, Nils
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medicine and Health Sciences, Radiology. Östergötlands Läns Landsting, Centre for Diagnostics, Department of Radiology in Linköping. Linköping University, Faculty of Health Sciences.
    Sandström, P
    Kihlberg, Johan
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medicine and Health Sciences, Radiology. Östergötlands Läns Landsting, Centre for Diagnostics, Department of Radiology in Linköping. Linköping University, Faculty of Health Sciences.
    Brismar, Torkel
    Karolinska institutet.
    Smedby, Örjan
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medicine and Health Sciences, Radiology. Östergötlands Läns Landsting, Centre for Diagnostics, Department of Radiology in Linköping. Linköping University, Faculty of Health Sciences.
    Lundberg, Peter
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medicine and Health Sciences, Radiation Physics. Linköping University, Department of Medicine and Health Sciences, Radiology. Östergötlands Läns Landsting, Centre for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics UHL. Östergötlands Läns Landsting, Centre for Diagnostics, Department of Radiology in Linköping. Linköping University, Faculty of Health Sciences.
    The hepatic uptake of Gd-EOB-DTPA is strongly correlated with the uptake of Gd-BOPTA2010Conference paper (Other academic)
  • 40.
    Dahlqvist Leinhard, Olof
    et al.
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Linköping University, Faculty of Health Sciences.
    Jacek, J.
    Aalto, Anne
    Linköping University, Department of Medicine and Health Sciences, Radiology . Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Medical Imaging.
    Grönqvist, A.
    Smedby, Örjan
    Linköping University, Department of Medicine and Health Sciences, Radiology . Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Medical Imaging.
    Landtblom, Anne-Marie
    Linköping University, Department of Clinical and Experimental Medicine. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Local Health Care Services in Central Östergötland, Department of Neurology.
    Lundberg, Peter
    Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics.
    Is Increased Normal White Matter Glutamate Concentration a Precursor of Gliosis and Disease Progression in Multiple Sclerosis?Manuscript (preprint) (Other academic)
    Abstract [en]

    Background: The multiple sclerosis (MS) severity scale (MSSS) is a new scoring procedure to clinically characterize the rate of disease progression in MS, rather than the disability of the patient. The latter is often characterized using the expanded disability status score (EDSS). The progress rate of the disease, magnetic resonance imaging (MRI)-based measures of ‘black hole lesions’, and atrophy have all been shown to be predicted well by MSSS. In this study we investigated possible relationships between brain metabolite concentrations, measured using proton (1H) magnetic resonance spectroscopy (MRS), and MSSS.

    Purpose: Our aims were to quantitatively investigate the metabolite concentrations in normal appearing white matter (NAWM) in MS-patients, and also to investigate possible correlations between disease subtype, EDSS and MSSS and metabolite concentrations. To minimize the interference from lesion contamination in the MRS measurement, a refined novel analysis procedure had to be developed in order to correct for partial volume effects in tissues near plaques.

    Materials and Methods: Forty eight patients with Clinically Definite MS (CDMS), and 18 normal control subjects (NC) were included retrospectively from several MRS studies. T1, T2, and proton density MRI, and four white matter 1H MRS single voxel PRESS (Point-REsolved SpectroScopy) spectra were acquired in each subject using echo time 35 ms and repetition time 6000 ms on a 1.5 T MR-scanner. A total of 108 examinations were acquired from patients and 18 from NC. Absolutely quantified NAWM metabolite concentrations were determined using a mixed linear model (MLM) analysis that included the degree of T2 lesion contamination in each voxel. The T2 lesion contamination of the MRS voxels was also used as an estimate of ‘lesion load’ at each exam. The corrected metabolite concentrations were then correlated with clinical measures of the patients’ status, including EDSS and MSSS.

    Results: The axonal marker N-acetyl aspartate (NAA) did not correlate with either EDSS or MSSS. The glial cell markers creatine and myo-inositol correlated positively with EDSS. Creatine and glutamate correlated positively with MSSS. The ‘estimated lesion load’ correlated positively not only with EDSS, but also with the number of bouts since disease onset. Importantly, it did not correlate with MSSS.

    Conclusion: The most interesting findings were the unchanged concentrations of NAA, and the concomitant increase of creatine and myo-inositol during the course of disease progression in MSpatients. These not only indicated a constant axonal density, but also that a simultaneous development of gliosis occurred. These processes are most likely linked to demyelination, as well as development of white matter atrophy, a process in which the demyelinated volume is replaced by the surrounding tissue leading to a net loss of white matter. As a consequence of this process, axons in NAWM are probably damaged, which leads to a higher concentration of glia cells relative to the axonal volume. The positive correlation that was found between MSSS, and the glutamate and creatine concentrations in NAWM, in combination with a complete lack of correlation between lesion load and MSSS, suggests that altered glutamate metabolism, and subsequent demyelination and gliosis, is an important pathophysiological mechanism in MS.

  • 41.
    Dahlqvist Leinhard, Olof
    et al.
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medicine and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Jarowski, J
    Gustavsson, M
    Tisell, Anders
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medicine and Health Sciences, Radiation Physics. Östergötlands Läns Landsting, Centre for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics UHL.
    Gladigau, D
    Landtblom, Anne-Marie
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Clinical and Experimental Medicine, Psychiatry. Östergötlands Läns Landsting, Sinnescentrum, Department of Neurosurgery UHL.
    Lundberg, Peter
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medicine and Health Sciences, Radiation Physics. Linköping University, Department of Medicine and Health Sciences, Radiology. Östergötlands Läns Landsting, Centre for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics UHL. Östergötlands Läns Landsting, Centre for Diagnostics, Department of Radiology in Linköping. Linköping University, Faculty of Health Sciences.
    Betainterferon treatment: Absolute quantification of white matter metabolites in patients with multiple sclerosis2008Conference paper (Other academic)
  • 42.
    Dahlqvist Leinhard, Olof
    et al.
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Jaworski, J,
    Östergötlands Läns Landsting, Local Health Care Services in Central Östergötland, Department of Neurology.
    Aalto, Anne
    Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Grönkvist, Anders
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences. Linköping University, Faculty of Health Sciences.
    Tisell, Anders
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiation Physics. Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics. Linköping University, Faculty of Health Sciences.
    Smedby, Örjan
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Landtblom, Anne-Marie
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Clinical and Experimental Medicine, Neurology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Local Health Care Services in Central Östergötland, Department of Neurology. Östergötlands Läns Landsting, Local Health Care Services in West Östergötland, Department of Medical Specialist in Motala.
    Lundberg, Peter
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Is Increased normal White Matter Glutamate Concentrations a Precursor of Gliosis and Disease Progression in Multiple Sclerosis?2011In: Internationell Society for Magnetic Resonance in Medicin, 2011, 2011, p. 4089-4089Conference paper (Refereed)
  • 43.
    Dahlqvist Leinhard, Olof
    et al.
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medicine and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Johansson, A
    Lundberg, Peter
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medicine and Health Sciences, Radiation Physics. Linköping University, Department of Medicine and Health Sciences, Radiology. Östergötlands Läns Landsting, Centre for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics UHL. Östergötlands Läns Landsting, Centre for Diagnostics, Department of Radiology in Linköping. Linköping University, Faculty of Health Sciences.
    Water-fat shift displacement artifact correction in two-point Dixon imaging2008Conference paper (Other academic)
  • 44.
    Dahlqvist Leinhard, Olof
    et al.
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Romu, Thobias
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Biomedical Engineering, Medical Informatics. Linköping University, The Institute of Technology.
    Karlsson, Anette
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Biomedical Engineering, Medical Informatics. Linköping University, The Institute of Technology.
    Borga, Magnus
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Biomedical Engineering, Medical Informatics. Linköping University, The Institute of Technology.
    High resolution isotropic whole-­‐body symmetrically sampled two point Dixon acquisition imaging at 3T2012In: ISMRM workshop on Fat-­‐Water Separation: Insights, Applications & Progress in MRI, 2012Conference paper (Other academic)
  • 45.
    Dahlqvist Leinhard, Olof
    et al.
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Romu, Thobias
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Biomedical Engineering, Medical Informatics. Linköping University, The Institute of Technology.
    Kihlberg, Johan
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences.
    Gjellan, Solveig
    Linköping University, Department of Medical and Health Sciences, Internal Medicine. Linköping University, Faculty of Health Sciences.
    Zanjani, Sepehr
    Linköping University, Department of Medical and Health Sciences, Internal Medicine. Linköping University, Faculty of Health Sciences.
    Smedby, Örjan
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Diagnostics, Department of Radiology in Linköping.
    Nyström, Fredrik
    Linköping University, Department of Medical and Health Sciences, Internal Medicine. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Centre, Department of Endocrinology.
    Borga, Magnus
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Biomedical Engineering, Medical Informatics. Linköping University, The Institute of Technology.
    Validation of whole-­‐body adipose tissue quantification using air displacement plethysmometry2012In: ISMRM workshop on Fat-­‐Water Separation: Insights, Applications & Progress in MRI, 2012Conference paper (Other academic)
  • 46.
    Dahlqvist Leinhard, Olof
    et al.
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medicine and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Warntjes, Marcel
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medicine and Health Sciences. Linköping University, Faculty of Health Sciences.
    Lundberg, Peter
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medicine and Health Sciences, Radiation Physics. Linköping University, Department of Medicine and Health Sciences, Radiology. Östergötlands Läns Landsting, Centre for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics UHL. Östergötlands Läns Landsting, Centre for Diagnostics, Department of Radiology in Linköping. Linköping University, Faculty of Health Sciences.
    Whole volume three dimensional B1 mapping in 10 second2008Conference paper (Other academic)
  • 47.
    Dahlström, Nils
    et al.
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medicine and Health Sciences, Radiology. Östergötlands Läns Landsting, Centre for Diagnostics, Department of Radiology in Linköping. Linköping University, Faculty of Health Sciences.
    Dahlqvist Leinhard, Olof
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medicine and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Brismar, Torkel
    Karolinska institutet.
    Sandström, P
    Kihlberg, Johan
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medicine and Health Sciences, Radiology. Östergötlands Läns Landsting, Centre for Diagnostics, Department of Radiology in Linköping. Linköping University, Faculty of Health Sciences.
    Lundberg, Peter
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medicine and Health Sciences, Radiation Physics. Linköping University, Department of Medicine and Health Sciences, Radiology. Östergötlands Läns Landsting, Centre for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics UHL. Östergötlands Läns Landsting, Centre for Diagnostics, Department of Radiology in Linköping. Linköping University, Faculty of Health Sciences.
    Smedby, Örjan
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medicine and Health Sciences, Radiology. Östergötlands Läns Landsting, Centre for Diagnostics, Department of Radiology in Linköping. Linköping University, Faculty of Health Sciences.
    Leverfunktionsundersökning med leverspecifikt MR-kontrastmedel2008Conference paper (Other academic)
  • 48.
    Dahlström, Nils
    et al.
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Dahlqvist Leinhard, Olof
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Kihlberg, Johan
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Quick, Petter
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Forsgren, Mikael
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics.
    Lundberg, Peter
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics.
    Persson, Anders
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Dual-Energy CT Detects Standard-Dose Gd-EOB-DTPA in the Hepatobiliary and Renal Systems of Patients Having Undergone Liver MRI2012Conference paper (Other academic)
  • 49.
    Dahlström, Nils
    et al.
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Dahlqvist Leinhard, Olof
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Sandström, Per
    Linköping University, Department of Clinical and Experimental Medicine, Surgery. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Surgery in Östergötland.
    Kihlberg, Johan
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Brismar, Torkel
    Karolinska Huddinge.
    Lundberg, Peter
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Smedby, Örjan
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Quantified hepatobiliary Gd-EOB-DTPA uptake rate reflects hepatobiliary function in patients2011Conference paper (Refereed)
  • 50.
    Dahlén, Johan
    et al.
    Linköping University, The Tema Institute, Department of Water and Environmental Studies. Linköping University, Faculty of Arts and Sciences.
    Karlsson, Stefan
    Linköping University, The Tema Institute, Department of Water and Environmental Studies. Linköping University, Faculty of Arts and Sciences.
    Bäckström, Mattias
    Man-Technology-Environment Research Centre, Örebro University.
    Hagberg, Jessica
    Man-Technology-Environment Research Centre, Örebro University.
    Pettersson, Håkan
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Determination of nitrate and other water quality parameters in groundwater from UV/VIS spectra employing partial least squares2000In: Chemosphere, ISSN 0045-6535, E-ISSN 1879-1298, Vol. 40, no 1, p. 71-77Article in journal (Refereed)
    Abstract [en]

    The use of UV/Vis spectroscopy in combination with partial least squares (PLS) regression for the simultaneous prediction of nitrate and non-purgeable organic carbon (NPOC) in groundwaters was evaluated. A model of high quality was obtained using first order derivative spectra in the range 200–300 nm. Inclusion of non-UV-absorbing constituents in the modeling procedure, i.e., chloride, sulfate, fluoride, total carbon (TC), inorganic carbon (IC), alkalinity, pH and conductivity was also evaluated. This model seemed to be useful for prediction of chloride, TC, IC, alkalinity and conductivity, while its ability to predict sulfate, fluoride and pH was poor. In conclusion, application of PLS regression, which requires neither filtration of samples nor addition of chemicals, is a promising alternative for fast interpretation of geochemical patterns of groundwater quality.

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