[en] The purpose of this study was to establish peripheral doses during stereotactic treatments. The doses to different organs were measured by thermoluminescence dosemeters. A simple power function can describe the relationship between the measured peripheral dose and the distance from target. The dependence of measured peripheral dose at a particular point on the collimator size can also be described be a simple exponential function. Leakage radiation contributes very little to the dose, but becomes dominant at distances of more than 50 cm from the target. The arrangement of arcs as well as the collimator size influence the magnitude of the peripheral dose due to the contribution of exit dose and due to the increasing scattering volume of target. By changing the arc arrangement and using smaller collimators one can reduce the peripheral dose significantly and minimise the total body radiation burden. (author)

[en] An improvement in the clinical results obtained using total body irradiation (TBI) with photon beams requires precise TBI treatment planning, reproducible irradiation, precise in vivo dosimetry, accurate documentation and careful evaluation. In vivo dosimetry using LiF Harshaw TLD-100 chips was used during the TBI treatments performed in our department. The results of in vivo thermoluminescence dosimetry (TLD) show that using TLD measurements and interactive adjustment of some treatment parameters based on these measurements, like monitor unit calculations, lung shielding thickness and patient positioning, it is possible to achieve high precision in absorbed dose delivery (less than 0.5%) as well as in homogeneity of irradiation (less than 6%). (author)

[en] The precision of stereotactic localization and volume determination was examined by using a Leksell's stereotactic frame, Leksell's MRI indicator box and Siemens 1 T MAGNETOM Expert scanner. The distortions in the spatial stereotactic coordinates and errors in volume determination were assessed through measurements employing a special phantom which simulated patient's head with different target volumes. The average geometrical distortion values gave evidence of a satisfactory precision for stereotactic MRI localization (average distortion 0.5 mm). No significant dependence of the magnitude of these distortions on the MRI examination sequence, MRI slice orientation, or spatial position of the measured point in the volume examined was observed. The mean percentage error of the volume determination determined by the technical capabilities of the imaging and treatment planning system was 10% for smaller volumes (below 2000 mm³) and 5% for larger volumes (above 10000 mm³). The subjective errors of volume determination were expressed as the standard deviation of mean volume calculated based on contours recorded by six independent observers (physicians) for each of five selected target volumes (meningioma, metastases, acoustic neurinoma, pituitary adenoma and arteriovenous malformation). The minimum standard deviation for volume recorded by six independent physicians was 5% (for metastases), the maximum value was 40 % (for arteriovenous malformation)

[en] The principles are given of the selection of tissue-equivalent materials and a survey is given of the properties of most frequently used tissue equivalent materials for photon radiation and electrons. The principles and methods are given for the determination of absorbed doses. Calorimetry, chemical dosimetry, the use of ionization chambers and their calibration are discussed. (J.P.)

No abstract available

[en] This study concentrated on assessment of the basic physical properties of a polymer gel dosimeter evaluated by NMR. For this, BANG-2 type polymer gel was prepared. The dosimeters were irradiated by ⁶⁰Co gamma photons and by 4, 6 and 18 MV X-ray photons for doses in the range 0-50 Gy. The multi-echo CPMG sequence was used for the evaluation of T₂-relaxation times in the irradiated gel dosimeters. Dependence of 1/T₂ in terms of the following factors was studied: absorbed dose, energy of applied radiation, temperature during NMR evaluation, time between irradiation and NMR evaluation and strength of the magnetic field. An exponential dependence of the 1/T₂ response on absorbed dose in the range 0-50 Gy was observed, while in the range 0-10 Gy the data could be fitted by a linear function. This paper also describes the dependence of 1/T₂ response on: radiation energy, strength of magnetic field and time from irradiation of the dosimeters to NMR evaluation. Increase of gel dosimeter 1/T₂ response with the decrease of the temperature during NMR evaluation has been quantitatively described. The polymer gel dosimetry system used in this study proved that it is a reliable system for three-dimensional dose distribution measurement. (author)

[en] The quantitative and qualitative parameters characterizing beams are described: energy flux density, particle flux density, absorbed dose, exposure, energy of ionizing radiation, depth dose distribution. (J.P.)

[en] Apart from historical aspects, the dissertation deals with standardization in clinical dosimetry (the notion of standardization, accuracy and precision required in clinical dosimetry and how inaccuracy is expressed, primary and secondary dosimetric laboratory), absorbed dose determination in clinical dosimetry (calibration of ionization chambers in Co-60 gamma beams, determination of absorbed dose in water, inaccuracies in clinical dosimetry), and quality assurance in clinical dosimetry (international and national audit of clinical dosimetry) (P.A.)

[en] The determination is described of the power output of irradiation sources, of parameters connected with the dose distribution in the irradiated object and of the dose from ⁶⁰Co gamma radiation in water by measuring exposure. The new concept of the calibration of ionization chambers, and conversion and perturbation factors are dealt with. (J.P.)

No abstract available