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A new method has been investigated for the mapping of dose distributions in three dimensions delivered by the Leksell gamma knife. The irradiation unit is used to selectively treat small volumes in the brain with single high doses of ionising radiation--a treatment procedure known as radiosurgery. The dosimetry method investigated utilises a dosimeter gel consisting of ferrous sulphate solution an
A method for the production of a tissue-mimicking phantom material for MR imaging is described. The material consists of a nickel-doped agarose gel. The T1 and T2 values of the gel can be varied independently by changing the relative amounts of nickel and agarose. Practically any T1 and T2 combination of clinical interest can be obtained. The long-term stability was studied and found to be good. T
The measurement of absorbed dose distributions using dosemeter gel and magnetic resonance imaging (MRI) in a standard geometry has been investigated. Absorbed depth-dose curves and profiles measured with this new technique show good agreement with corresponding measurements using diodes. This was proven in a 60Co beam as well as an electron beam. The dosemeter gel is made of agarose and ferrous su
When a pinhole collimator is to be used for tomographic studies the standard SPECT software has to be modified so as to avoid serious image distortion outside the axis of rotation. The MTF measured at the axis of rotation shows that the better resolution of the pinhole collimator as compared with that of a parallel-hole collimator improves the tomographic image. The low sensitivity of the pinhole
In 50 patients with primary hyperparathyroidism, investigation before initial neck exploration included ultrasonography, computed tomography and 99technetium-201thallium subtraction scintigraphy. The sensitivity for correct preoperative localization was 50%, 54% and 56%, respectively. There was marked inter-observer variation in assessment of ultrasonography and computed tomography, while scintigr
Two gels have been found to be suitable to load with ferrous sulphate solution. In these soft tissue equivalent phantoms, the absorbed dose distribution can be measured after irradiation in clinically used MR imaging equipment. The present studies were carried out using a 0.25 T NMR analyser without imaging properties. A ferrous sulphate solution, 0.05 M with respect to sulphuric acid, can be gell
Activation products which contribute significantly to the exposure of the staff operating the accelerator were found in the accelerator head in the transparent holder for the lead blocks and in the 60 degrees wedge filter made of lead. A proper choice of material in these parts of the accelerator could easily reduce this exposure without excessive changes in the construction. The absorbed dose-rat
BACKGROUND: Ulcerative colitis and Crohn's disease are the major chronic inflammatory bowel diseases affecting the gastrointestinal tract in humans. Imaging techniques such as endoscopy and computed tomography are used to monitor disease activity. Magnetic resonance imaging (MRI) is emerging as a diagnostic modality, and studies have shown that MRI can be used in the diagnostic procedure of patien
The purpose of this research was to investigate the geometrical accuracy of magnetic resonance (MR) images used in the radiation therapy treatment planning for lung cancer. In this study, the capability of MR imaging to acquire dynamic two-dimensional images was explored to access the motion of lung tumors. Due to a number of factors, including the use of a large field-of-view for the thorax, MR i
Politisk komedi är en hybridgenre där politiska nyheter och analyser blandas med komedi och underhållning. Allt eftersom politisk komedi ökar i popularitet – i de flesta medieformer och nationella kontexter – arbetar forskare med att förstå dess roll i relation till medborgarskap, och det kan konstateras att genren utmanar den vetenskapliga förståelsen av politiska medier och medborgarskap. Denna Political comedy is a hybrid genre that mixes political news and analysis with comedy and entertainment. As it becomes more and more popular in most media forms and national contexts, researchers struggle to understand its role in relation to other types of political media, and of citizenship; in this sense, it challenges scholarly conceptualisation of political media and citizenship. Thus, this t
A recently developed method for quantitative assessment of regional lung ventilation was employed for the study of posture-dependent ventilation differences in rats. The measurement employed hyperpolarized (3)He MRI to detect the build-up of the signal intensity after increasing numbers of (3)He breaths, which allowed for computation of a regional ventilation parameter. A group of six anesthetized
Background: Chronic pain is common in older adults, yet little is known of its development in old age. Although fear-avoidance beliefs in chronic pain have been explored in younger adults, the relationship between chronic pain, kinesiophobia and physical activity levels has not been investigated in older adults.Objectives: The overall aim was to explore prevalence, development and related factors
A new technique for assessing tissue blood flow using hyperpolarized tracers, based on the fact that the magnetization of a hyperpolarized substance can be destroyed permanently, is described. Assessments of blood flow with this technique are inherently insensitive to arterial delay and dispersion, and allow for quantification of the transit time and dispersion in the arteries that supply the inve
