Vergleich von Thermolumineszenzdosimetern und Halbleiterdetektoren in der Kleinfelddosimetrie für präklinische Anwendungen in der Strahlentherapie

Abstract

Radiotherapy is an essential component in the treatment of tumours. Dosimetry is the art of characterizing and measuring radiation dose and is key in treatment, research, and quality assurance of radiation oncology. Dosimetry of small radiation fields is particularly challenging due to technical and physical conditions. For example, the Bragg-Gray cavity theory, the shielding of the focal spot, the range of the secondary electrons, and the volume effect have a major influence on the measurement of dose. In this work, thermoluminescence dosimeters are compared with solid state detectors in small X-ray fields. The aim is to investigate if thermoluminescence dosimeters are also suited for dose measurements under these conditions. For this purpose, both dosimeters were irradiated with 200 kV X-rays. They were irradiated at different depths and with different collimator sizes. The penetration depths were 1mm, 5mm, 10mm, 15mm, 20mm, 35mm and 50mm and the collimator sizes were 5mm, 7mm, 8mm, 10mm, 15mm, 20mm, 25mm, 30mm and no collimation. When handling the thermoluminescence dosimeters care must be taken during the readout process and the annihilation process, as outlined in this thesis. To be able to compare the data from both detector-systems data was normalized to 8mm collimation at 20mm depth. Statistical analysis was performed by descriptive methods as well as inferential statistic methods to determine differences in the dose curves for each dosimeters. The results showed similar depth dose curves for both dosemeters. As no significant difference between the dosemeters was observed, thermoluminescence dosimeters are also suited to dosimetrically characterize small fields in X-rays. Due to the workflow and the time required when working with thermoluminescence dosimeters, this detector system is not fully applicable in clinical routine. Although the read-out of solid-state detectors is immediately, they must be connected to an electrometer, making it impossible to implant them in an organism. It can therefore be concluded that both detector systems have advantages and disadvantages. Furthermore, the results of this work have opened various possibilities for further work. In addition, the use of thermoluminescence dosimeters in preclinical particle therapy will be explored in the near future.

Date of Award	2024
Original language	German (Austria)
Supervisor	Peter Kuess (Supervisor) & Mario Scheweder (Supervisor)