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Evaluation of the Dosimetric Properties of a Diode Detector to Proton Radiosurgery

A Wroe

A Teran1,2 , G McAuley3 , J D Slater1 , J M Slater3 , A Wroe1*, (1) Loma Linda University Medical Center, Loma Linda, CA, (2) San Diego State University, San Diego, CA, (3) Loma Linda University, Loma Linda, California


SU-E-T-446 Sunday 3:00PM - 6:00PM Room: Exhibit Hall

Purpose: To test the PTW PR60020 proton dosimetry diode in radiation fields relevant to proton radiosurgery applications and evaluate its suitability as a high resolution, real time dosimetry device.

Methods: Data was collected using our standard nominal radiosurgery energies of 126 MeV and 155 MeV through a single stage scattering system, corresponding to a range of 9.7 and 15 cm in water respectively. Various beam modulations were tested as part of this study. Depth dose and beam profile measurements were completed with the PTW PR60020 dosimetry diode with comparative measurements using a PTW Markus ionization chamber and EBT2 Gafchromic film. Monte Carlo simulations were also completed for comparison.

Results: The single 1 mm² by 20 μm thick sensitive volume allowed for high spatial resolution measurements while maintaining sufficient sensitive volume to ensure that measurements could be completed without excessive beam delivery. Depth dose profiles exhibited negligible LET dependence which typically impacts film and other solid state dosimetry devices, while beam ranges measured with the PTW diode were within 1 mm of ion chamber data. In an edge on arrangement beam profiles were also measured within 0.5 mm full-width at half-maximum at various depths as compared to film and simulation data.

Conclusion: The PTW PR60020 proved to be a very useful radiation metrology apparatus for proton radiosurgery applications. Its waterproof and rugged construction allowed for easy deployment in phantoms or water tanks that are commonly used in proton radiosurgery QA. Dosimetrically, the diode exhibited negligible LET dependence as a function of depth, while in edge on arrangement to the incident proton beam it facilitated the measurement of beam profiles with a spatial resolution comparable to both Monte Carlo and film measurements.

Funding Support, Disclosures, and Conflict of Interest: This project was sponsored in part by funding from the Department of Defense (DOD# W81XWH-BAA-10-1).

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