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A 3 Dimensional Prompt Gamma Imaging System for Range Verification in Proton Radiotherapy

J Polf

E Draeger1 , H Chen1 , D Mackin2 , S Peterson3 , S Avery4 , S Beddar2 , J Polf1*, (1) University of Maryland School of Medicine, Baltimore, MD, (2) MD Anderson Cancer Center, Houston, TX, (4) University of Cape Town, Rondebosch, South Africa, (5) University of Pennsylvania, Philadelphia, PA


TU-FG-BRB-5 (Tuesday, August 2, 2016) 1:45 PM - 3:45 PM Room: Ballroom B

Purpose: To report on the initial developments of a clinical 3-dimensional (3D) prompt gamma (PG) imaging system for proton radiotherapy range verification.

Methods: The new imaging system under development consists of a prototype Compton camera to measure PG emission during proton beam irradiation and software to reconstruct, display, and analyze 3D images of the PG emission. For initial test of the system, PGs were measured with a prototype CC during a 200 cGy dose delivery with clinical proton pencil beams (ranging from 100 MeV – 200 MeV) to a water phantom. Measurements were also carried out with the CC placed 15 cm from the phantom for a full range 150 MeV pencil beam and with its range shifted by 2 mm. Reconstructed images of the PG emission were displayed by the clinical PG imaging software and compared to the dose distributions of the proton beams calculated by a commercial treatment planning system.

Results: Measurements made with the new PG imaging system showed that a 3D image could be reconstructed from PGs measured during the delivery of 200 cGy of dose, and that shifts in the Bragg peak range of as little as 2 mm could be detected.

Conclusion: Initial tests of a new PG imaging system show its potential to provide 3D imaging and range verification for proton radiotherapy. Based on these results, we have begun work to improve the system with the goal that images can be produced from delivery of as little as 20 cGy so that the system could be used for in-vivo proton beam range verification on a daily basis.

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