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UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS Guest
2024-11-25 0:01 |
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Conference: Bucharest University Faculty of Physics 2012 Meeting
Section: Biophysics; Medical Physics
Title:
A clinical assessment of IMRT dose distribution using the gamma index evaluation and a 2D ion chamber detector array
Authors:
M. DUMITRACHE (1), Alina TĂNASE (2)
Affiliation:
Institute of Oncology, „Prof. Dr. Al. Trestioreanu”, Bucharest, Romania (1)
Emergency Central Military Hospital, „Carol Davila”, Bucharest, Romania (2)
E-mail
mihai149@yahoo.com
alinatanasemail@yahoo.com
Keywords:
gamma index, intensity modulated radiation therapy, quality assurance
Abstract:
The evaluation between measured and calculated dose distribution plays an essential role in the quality assurance (QA) procedures for intensity modulated radiation therapy (IMRT). Generally, 3D dose distribution obtained from a treatment planning system (TPS) has to be verified by dosimetric methods. This study evaluates the gamma index for a clinical prostate IMRT case in order to quantitatively compare dose distributions (measured and calculated). Before computing gamma index, the dose and distance scales of the two distributions, referred to as evaluated and reference, are renormalized by dose and distance criteria, respectively. The renormalization allows the dose distribution comparison to be conducted simultaneously along dose and distance axes. The gamma index, independently calculated for each reference point, is the minimum distance in the renormalized multidimensional space between the evaluated distribution and the reference point. Usually, the gamma index degenerates to the dose-difference and distance-to-agreement tests in shallow and very steep dose gradient regions. In these situations more attention in evaluation process is needed.
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