Unit:
Κατεύθυνση Ιατρική Φυσική-ΑκτινοφυσικήLibrary of the School of Health Sciences
Author:
Bitzios Vasileios
Supervisors info:
Παντελής Καραΐσκος, Καθηγητής, Ιατρική, ΕΚΠΑ
Παναγιώτης Παπαγιάννης, Αναπληρωτής καθηγητής, Ιατρική, ΕΚΠΑ
Κωνσταντίνος Λουκάς, Επίκουρος καθηγητής, Ιατρική, ΕΚΠΑ
Original Title:
Χρήση δοσιμέτρων θερμοφωταύγειας (TLD) για τον ποιοτικό έλεγχο εξελιγμένων τεχνικών ακτινοθεραπείας
Translated title:
Use of thermoluminescent dosimeters (TLD) for quality control of developed radiotherapy techniques
Summary:
Over 50% of patients with cancer undergo radiotherapy, which is either the primary treatment method, or it assists with chemotherapy or surgical removal. The precise planning of the treatment plan and its confirmation is a prerequisite for the optimal outcome. This work focuses on the confirmation of modern radiotherapy techniques with thermoluminescent dosimeters (TLDs). At a first level the different dosimeters used in radiotherapy as well as the comparison methods are discussed. A systematic review of the various modern radiotherapy techniques, highlighting the advantages and disadvantages of each method is also included.
In the experimental part of the work, the experimental confirmation of modern radiotherapy techniques using TLD dosimeters using two different dosimeter reader systems, is performed. For this purpose, calibration of 97 TLDs of 1x1x1mm3 resistances was initially performed. The dosimeters were then used to confirm distributions of rotational radiotherapy applications with VMAT at multiple points on the same level using a special model. Dose maps were constructed at the measurement points and a number of criteria such as γ-index and point to point comparison were applied for the quantitative comparison of experimental and theoretical distributions.
The evaluation of the dosimetric results showed a relatively good agreement between the theoretical and experimental dose distribution, especially the global error. It has emerged that g-index is the ideal technique especially when using modern radiotherapy techniques (IMRT, VMAT) because it takes into account all parameters such as the relative dose difference and distance to agreement. Multiple dose and distance ranges from 7% / 2mm to 5% / 1mm were selected for γ-index. The results in both treatment plans were quite satisfactory and, especially in the case of the global γ-index, the passing rate was almost in all cases over 90%.
Regarding the correlations, a statistically significant dependence was found between the error and the dose recorded by the TLDs. At lower doses, greater deviations were observed than were present at high doses. Also common in both was the positive dependence that existed between the error and the distance from the isocenter, the bigger the distance from the isocenter, the greater deviations were observed.
Main subject category:
Health Sciences
Keywords:
TLD dosimetry, Calibration TLD-reader, VMAT, Point to point comparison, Γ-index, Local error, Global error
File:
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ΜΠΙΤΖΙΟΣ ΒΑΣΙΛΕΙΟΣ.pdf
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