Measurement of dose distributions for high energy photo beams using thermoluminescence dosimeter

Abstract

In this work, the dose distribution of high-energy photon beams was measured using thermoluminescence (TL) dosimeters. The purpose of this work was to introduce the TLDs in clinical dose measurements, which are normally done with ion chamber dosimeter. For this, the rod of 1 x 1 x 6 mm3 size of TLD was used. Most of the measurements were carried out for the photon beams of energies 4.0 & 10MV. The reliability of the detector was tested by comparison with an ionchamber and a Markus chamber dosimeter. Chapter 1 describes the scope and aim of the studies. Here, the quality of the high-energy photon beams, which comprises the prime conditions of radiotherapy treatment, is also discussed. In chapter 2, 3 and 4, the review of some related works, theoretical aspects of thermoluminescence including glow curve theory and some necessary equipment have been discussed. In chapter 5 and 6, the reproducibility of the TLDs via the thermal treatment in four-step application cycle of TLD, the sensitivity factor and calibration of the TLDs have been discussed. Detail studies with the practical problems including those associated with the annealing, storage, handling, irradiation, readout and calibration have also been discussed. In chapter 7 and 8, the technique of dose accuracy has been established through some homogeneous and inhomogeneous measurements. Here, the independent characteristics of field sizes, depths of phantom for TL-dosimeter like ionchamber dosimetry were obtained through those measurements. Chapter 9 describes the uses of TLDs in invivo dosimetry by following a new methodology. The entrance and exit dose was measured using TLDs. The method provides more accurate target dose (within 0.17% variation from the direct target dose value). Chapter 10 describes the development of a new PC program for treatment of cancer using multiple asymmetric fields and its experimental verification. Chapter 11 describes the use of TLDs for measuring dose during whole body irradiation with high-energy photon beams. Finally, in Chapter 12, the findings of the experiments are discussed.