Διατμηματικό ΠΜΣ Ιατρική Φυσική-Ακτινοφυσική
Library of the School of Health Sciences

2017-06-16

2017

Chatonidis Vasileios

Παναγιώτης Παπαγιάννης, Αναπληρωτής Καθηγητής, Ιατρική Σχολή, Εθνικό και Καποδιστριακό Πανεπιστήμιο Αθηνών
Παντελής Καραΐσκος, Αναπληρωτής Καθηγητής, Ιατρική Σχολή, Εθνικό και Καποδιστριακό Πανεπιστήμιο Αθηνών
Κωνσταντίνος Λουκάς, Επίκουρος Καθηγητής, Ιατρική Σχολή, Εθνικό και Καποδιστριακό Πανεπιστήμιο Αθηνών

Τρισδιάστατη δοσιμετρία ακτινοθεραπευτικών εφαρμογών με χρήση χημικών δοσιμέτρων - οπτικής υπολογιστικής τομογραφίας

Greek

Three-dimensional dosimetry of radiotherapy applications using chemical dosimeters - optical computed tomography

This thesis focuses on the experimental dosimetric validation of a surface tumor brachytherapy plan with the implementation of radiochromic dosimeters, using the method of optical computed tomography (OCT). Basic properties of Vista™ optical-CT scanner in combination with TrueView™ gel dosimeters described in detail as well. An electron beam of 18 MeV and a field size of 5 cm x 5 cm applied to calibrate the dosimeter. The linear relationship between the change in optical attenuation and the absorbed dose was calculated. The irradiation plan delivery was administered to the dosimeter with an HDR remote afterloading unit, equipped with an 192Ir source. Upon optical scan of the irradiated dosimeters, 512 projections were obtained. The reconstruction resolution was 0.5 mm in plane, with a fixed sectional separation of 0.5 mm. Absorption measurements displayed optical perturbations caused by stray light into the system, generating artifacts upon reconstruction. All DICOM images were uploaded to the polyGeVero® software for spatial co-registration and processing. Dosimetric comparison performed between the experimental dose data obtained by gel and their corresponding calculation by TPS using the two integrated dosimetry algorithms, TG-43 and ACE. Both qualitative and quantitative tools applied, including dose profiles, isodose curves superposition, dose-volume histograms and gamma maps (global and local) with acceptance criteria of 5 % dose difference and 2 mm distance to agreement. ACE algorithm demonstrated better agreement with the experimental results than the algorithm based on TG-43 formalism. The gamma index distributions of the comparison between experimental gel dose and TPS calculations showed strong agreement (γ <1) for most of the dosimeter volume, with exemption of the areas within a few millimeters of the dosimeter walls due to artifacts as well as areas of low dose and low dose gradients away from dwell positions of the source.

Health Sciences

Brachytherapy, Dosimetry, Validation, Gamma index, Radiochromic gel, Optical Computed Tomography, Treatment plan

No

0

Yes

78

141

File access is restricted only to the intranet of UoA.

https://pergamos.lib.uoa.gr/uoa/dl/object/1668164