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SU‐F‐T‐178: Optimized Design of a Diamond Detector Specifically Dedicated to the Dose Distribution Measurements in Clinical Proton Pencil Beams
Author(s) -
Moignier C,
Tromson D,
Marsolat F,
De Marzi L,
Pomorski M,
Agelou M,
Hernandez J Garcia,
Lazaro D,
Mazal A
Publication year - 2016
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.4956315
Subject(s) - proton therapy , dosimetry , pencil beam scanning , ionization chamber , dosimeter , monte carlo method , materials science , collimator , pencil (optics) , proton , bragg peak , beam (structure) , optics , dose profile , full width at half maximum , diamond , absorbed dose , nuclear medicine , physics , nuclear physics , ionization , ion , mathematics , medicine , statistics , quantum mechanics , composite material
Purpose: In proton‐therapy, pencil beam scanning (PBS) dosimetry presents a real challenge due to the small size of the beam (about 3 to 8 mm in FWHM), the pulsed high dose rate (up to 100 Gy/s) and the proton energy variation (about 30 MeV to 250 MeV). In the framework of French INSERM DEDIPRO project, a specifically dedicated single crystal diamond dosimeter (SCDDo) was developed with the objective of obtaining accurate measurements of the dose distribution in PBS modality. Methods: Monte Carlo simulations with MCNPX were performed. A small proton beam of 5 mm in FWHM was simulated as well as diamond devices with various size, thickness and holder composition. The calculated doses‐to‐diamond were compared with the doses‐to‐water in order to reduce the perturbation effects. Monte‐Carlo simulations lead to an optimized SCDDo design for small proton beams dosimetry. Following the optimized design, SCDDos were mounted in water‐equivalent holders with electrical connection adapted to standard electrometer. First, SCDDos performances (stability, repeatability, signal‐to‐background ratio…) were evaluated with conventional photon beams. Then, characterizations (dose linearity, dose rate dependence…) with wide proton beams were performed at proton‐therapy center (IC‐CPO) from Curie Institute (France) with the passive proton delivery technique, in order to confirm dosimetric requirements. Finally, depth‐dose distributions were measured in a water tank, for native and modulated Bragg Peaks with the collimator of 12 cm, and compared to a commercial PPC05 parallel‐plate ionization chamber reference detector. Lateral‐dose profiles were also measured with the collimator of 5 mm, and compared to a commercial SFD diode. Results: The results show that SCDDo design does not disturb the dose distributions. Conclusion: The experimental dose distributions with the SCDDo are in good agreement with the commercial detectors and no energy dependence was observed with this device configuration.