Dosimetry in Gynaecology and Treatment Verification in Electronic Brachytherapy

• Main Author: Lozares, Sergio Alberto
• Format: Dissertation
• Language: Spanish
• Published: ProQuest Dissertations & Theses 01-01-2021
• Subjects: Atomic physics; Physics
• ISBN: 9798762109314

Dosimetry in gynaecology and treatment verification in electronic brachytherapy, aims to assess and discuss the absorbed dose values in different clinical applications of electronic brachytherapy. The source used in these systems consists of a 10 mm long, 2 mm diameter vacuum tube enclosed in a 5.6 mm diameter cooling catheter, typically operating at 50 kVp. In particular, it focuses on gynaecological treatments for endometrial and cervical cancer, presenting the first clinical results obtained and comparing them with those that would have been obtained if the treatments had been performed with conventional brachytherapy equipment based on radioactive isotopes. The design of the Axxent system makes its adaptation to intracavitary gynaecological treatments optimal, allowing it to treat endometrial cancer and, in addition, it is the only eBT system capable of treating cervical cancer. The advantages that the system can provide over conventional brachytherapy are discussed, and in which cases it could be a good complement to the latter, or a suitable alternative in certain cases or socio-economic conditions. In addition, in the fourth chapter, another type of treatment with this system is presented, namely intraoperative breast radiotherapy treatments. In this case, the objective is to verify the absorbed doses both in the tumour bed after surgery and in the organs at risk. This in vivo dosimetry process is carried out using radiochromic films placed directly in the surgical field. Proper handling of these detectors, as well as rigorous calibration, are key to achieving the proposed objectives. In vivo dosimetry makes it possible to verify whether treatments are being carried out properly, as well as to endorse the absorbed doses calculated by the treatment planning system. Calculation systems with low-energy photons are less developed than for other treatment modalities in radiation oncology. Therefore, this type of study reliably controls the absorbed dose, particularly in the areas furthest away from the source, and therefore those with the greatest calculation uncertainty, and the absorbed dose values in different areas are compared depending on the distance from the source; in this way, there will be a different calibration curve for the radiochromic film, depending on the area in which it is measured, thus taking into account the hardening of the beam. Finally, in chapter 5, we will see which of the supposed advantages of this system are fulfilled, what room for improvement is found and what possible disadvantages are observed.