Mattias Karlsson

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Electrical resistance of skin was studied with the aid of a specially designed meter that compared the resistance per surface area of small skin points with that of the surrounding skin. In a systematic study of the hands, face and ears in five subjects low-resistance skin points were repeatedly found in characteristic loci, comparable in different(More)
MRI provides unsurpassed soft tissue contrast, but the inherent low sensitivity of this modality has limited the clinical use to imaging of water protons. With hyperpolarization techniques, the signal from a given number of nuclear spins can be raised more than 100 000 times. The strong signal enhancement enables imaging of nuclei other than protons, e.g.(More)
Coarctation of the aorta causes arterial hypertension in the upper body and a low blood pressure downstream. Collateral blood vessels compensate by reducing the downstream pressure drop. To study the effect of various coarctation and collateral properties, we designed a computer model of the arterial circulation. The model contains a flow source and a(More)
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(More)
Standard treatment machines for external radiotherapy are designed to yield flat dose distributions at a representative treatment depth. The common method to reach this goal is to use a flattening filter to decrease the fluence in the centre of the beam. A side effect of this filtering is that the average energy of the beam is generally lower at a distance(More)
PURPOSE At St. Erik Eye Hospital in Stockholm, Sweden, ocular tumors of apical height above 6 mm are treated with brachytherapy, using iodine-125 seeds attached to a gold alloy plaque while the treatment planning is performed assuming homogeneous water surroundings. The aim of this work was to investigate the dose-modifying effects of the plaque and the(More)
The aim of the study was to assess the relative number of bone trabeculae in different orientations by using magnetic inhomogeneity measurements by MR imaging. Twelve defatted human vertebrae (L2–L4) were studied by MR imaging and CT. In the MR measurements the reversible transaxial decay rate, R2', was determined using the GESFIDE sequence. The relative(More)
The aim of this study was to investigate whether MR imaging of trabecular bone structure using magnetic inhomogeneity measurements is related to the amount of bone mineral in human vertebrae. Weight, bone mineral content (BMCDXA), bone mineral per area (BMADXA) and bone mineral density (BMDCT) were determined in 12 defatted human lumbar vertebrae (L2–L4) by(More)
  • M Karlsson
  • Medical dosimetry : official journal of the…
  • 1997
An EDW field is in principle a sum of fields with different sizes. The Helax TMS 3.1 dose planning system uses pre-existing open beam data and information specific to the geometry of the accelerator treatment head including flattening filter and collimators to generate open fields. These open fields are then summed using the Segmented Treatment Tables (STT)(More)