First Demonstration of a Prompt Gamma Slit‐Camera for in Vivo Proton Range Verification Based On Semiconductor Detectors

Authors

H. Wang, University of Nevada, Las VegasFollow
Y. Lu, University of Nevada, Las Vegas
Yu Kuang, University of Nevada, Las VegasFollow

Document Type

Abstract

Publication Date

6-11-2018

Publication Title

Medical Physics

Volume

45

Issue

6

First page number:

E509

Last page number:

E509

Abstract

Purpose: To demonstrate the feasibility of using a solid‐state semiconductor slit‐camera in prompt gamma imaging (PGI) for proton range verification during proton therapy with pencil beam scanning mode. Methods: The PGI system based on an array of semiconductor detectors was designed using TOPAS Monte Carlo tool. An array of CZT detectors with a 6‐mm‐width knife‐edge shaped slit tungsten collimator was used to project the prompt gamma depth emission profiles produced by proton beams in a patient phantom. The detector array contains 40 individual CZT detectors arranged in two rows to score events between 3 and 6 MeV. Each detector is 20 mm thick, 100 mm high, 4 mm wide along the beam axis. The built‐in scanning nozzle worked in pencil beam scanning mode. To demonstrate the utility of the camera for range verification, the axial beam shifting in a PMMA cylinder and ranges of the distal beam spots in the central slice of C‐Shape dose delivery in the TG‐119 phantom were measured, respectively. Results: The energy spectra measured from prompt gamma emission in PMMA irradiated with 160 MeV proton beam show the 4.44 MeV peak from de‐excitation of ¹²C. The gamma emission between 4.0 and 5.0 MeV contributed to the majority of detected profiles. With the collimator at 15 cm away from the beam axis, a 1 mm standard deviation on range estimation in PMMA phantom irradiated with the pencil beams of 2.2 × 10⁸ protons at 160 MeV can be achieved. With the collimator at 25 cm away from the beam axis, a 3 mm standard deviation on range estimation in TG‐119 phantom for the distal beam spots was obtained. Conclusion: Results confirmed the feasibility of the PGI system based on a CZT semiconductor slit‐camera for range monitoring with millimeter accuracy using pencil beam scanning mode in a typical clinical setting.

Disciplines

Medicine and Health Sciences

Language

English

Repository Citation

Wang, H., Lu, Y., Kuang, Y. (2018). First Demonstration of a Prompt Gamma Slit‐Camera for in Vivo Proton Range Verification Based On Semiconductor Detectors. Medical Physics, 45(6), E509-E509.