IMPACT OF CALIBRATION CURVE PRECISION ON RESULTS OF IMRT VERIFICATION WITH EBT3 FILMS

Result code in IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F68407700%3A21340%2F16%3A00300588" target="_blank" >RIV/68407700:21340/16:00300588 - isvavai.cz</a>

Result on the web

<a href="http://www.rad-proceedings.org/paper.php?id=28" target="_blank" >http://www.rad-proceedings.org/paper.php?id=28</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.21175/RadProc.2016.13" target="_blank" >10.21175/RadProc.2016.13</a>

Result language

angličtina

Original language name

IMPACT OF CALIBRATION CURVE PRECISION ON RESULTS OF IMRT VERIFICATION WITH EBT3 FILMS

Original language description

This study aims to establish proper methodology for IMRT treatment plan verification using EBT3 film dosimetry. This preliminary part focuses on proper calibration curve fitting and its impact on the results of gamma analysis. First, scanner and film properties were tested. The films in use were Gafchromic EBT3 together with EPSON Perfection V700 Photo scanner. Three sets of calibration points were obtained for the EBT3 film. Irradiation was carried out on a Siemens Artiste linear accelerator in the Thomayer Hospital in Prague, using the photon energy 18MV. Film pieces of approximately 6 x 6 cm2 were irradiated with 16 doses ranging from 0 to 12 Gy in an RW3 slab phantom in reference conditions. Three sets of films of the same calibration doses were irradiated in three subsequent weeks and scanned in two different ways, changing the scanned region of interest. The mean value of each scanned piece of film was taken as one calibration point. Different calibration curves were obtained in MATLAB, Excel and FilmQA Pro. Both polynomial fits with a fourth degree polynomial and rational functions as proposed in FilmQA Pro were assessed. Other films were irradiated with an IMRT plan for prostate and lymph nodes. The plan contained 5 fields with 18MV photon beams and each field was tested separately with the gantry position at 0°. Films were placed into the coronal isocentric plane of an RW3 slab phantom. They were scanned using the same protocol as for the calibration films, fitted with the different calibration curves in MATLAB and evaluated in OmniPro I’mRT software using gamma analysis with 4 %/3 mm criteria. Different gamma pass rates for the very same fields could be seen when different calibration scenarios were applied. These differences in gamma pass rates were not negligible, even when the estimated precision of calibration curves was similar. Best results were obtained with a MATLAB curve when three sets of calibration films were averaged out.

Czech name

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Czech description

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Type

D - Article in proceedings

CEP classification

BG - Nuclear, atomic and molecular physics, accelerators

OECD FORD branch

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Project

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Continuities

S - Specificky vyzkum na vysokych skolach

Publication year

2016

Confidentiality

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Article name in the collection

RAD Conference Proceedings

ISBN

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ISSN

2466-4626

e-ISSN

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Number of pages

6

Pages from-to

49-54

Publisher name

RAD Association, Niš, Serbia

Place of publication

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Event location

Niš

Event date

May 23, 2016

Type of event by nationality

WRD - Celosvětová akce

UT code for WoS article

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