ETD

Digital archive of theses discussed at the University of Pisa

 

Thesis etd-11182021-184146


Thesis type
Tesi di specializzazione (3 anni)
Author
BORGHERESI, RITA
URN
etd-11182021-184146
Thesis title
Commissioning and experimental validation beyond highly heterogeneous media of Eclipse dose-calculation algorithms
Department
FISICA
Course of study
FISICA MEDICA
Supervisors
relatore Dott.ssa Linsalata, Stefania
Keywords
  • LINAC
  • commissioning
  • heterogeneity
  • PTW-LA48
  • EBT3
  • dose calculation algorithm
Graduation session start date
07/12/2021
Availability
None
Release date
07/12/2091
Summary
During the last decade, the capabilities of image-based commercial TPS have been enhanced due to developments in treatment imaging, planning, and delivery. The accurate delivery of IMRT and VMAT treatments strongly depends on the proper commissioning and testing of TPSs.
The aim of this thesis work is to provide the fundamental set of tests performed for the commissioning of a Varian Eclipse planning system on a Varian Clinac DHX, focusing on tests performed to assess the accuracy of photon dose calculation algorithms (i.e AXB and AAA) in presence of highly heterogeneous media.
The importance of this study was related to the increasing use of metal medical devices, such as prostheses or dental implants. Currently, commercially available photon dose calculation algorithms are a well-established tool for the prediction of adsorbed dose in inhomogeneous media, for the density range of the human body; nevertheless, their accuracy needs to be validated also in presence of high-density materials.
Absolute dose longitudinal profiles were measured using GafChromic EBT3 films and a PTW-LA48 linear ionization chamber array downward a heterogeneity insert. The insert materials range from low-Z material like lung to the higher ones, like titanium. The dose algorithms accuracy was evaluated comparing measured and calculated dose profiles. The absolute dose profiles in water were calculated replicating the real setup in Eclipse TPS using two different procedures i.e., performing a TC scan of the phantom or manually drawing a virtual phantom. In the second case, the absorbed dose was calculated performing the density override of the materials. Investigations were performed for 6 MV and 15 MV photons.
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