Room: AAPM ePoster Library
Purpose: Proton imaging has a potential for reduction of range uncertainty in proton therapy treatment planning. However, motion artifact in proton imaging has not been studied yet. A respiratory synchronization technique can improve proton imaging of a moving target. The purpose of this study is to develop a gated proton imaging system for moving target using a fiducial marker and a dual X-ray fluoroscopy system.
Methods: A gated proton imaging system was developed based on proton imaging system using volumetric scintillator and a camera. All protons stop in thick scintillator and the scintillation light integrated along the beam path was measured by a camera with two-dimensional spatial resolution. In addition to this system, a real-time tumor monitoring system was incorporated using a fiducial marker and an orthogonal X-ray fluoroscopy system. The beam was gated using the three-dimensional position of gold marker with diameter of 1.5 mm. We demonstrated the gated proton imaging system using 200-MeV and 70-MeV proton spot-scanning beam with 5×10 cm2 irradiation field. Breathing motion was mimicked as sinusoidal curve with a translational stage. We acquired proton radiography (pRG) images in three cases; a static object, a moving target without gating and a moving target with gating as a gated proton pRG image.
Results: A gated pRG image was successfully acquired and the quality was obviously improved compared to a pRG image of a moving object without gating. Deterioration around boundary of objects and shift of the acquired image was observed in a gated pRG image, depending on a gating window size, gating latency, frequency of X-ray image for gating and the direction of beam scanning.
Conclusion: We developed a gated proton imaging system with a fiducial marker and dual X-ray fluoroscopy system and successfully acquired a gated proton radiography of a moving object experimentally.
Funding Support, Disclosures, and Conflict of Interest: This work was supported by JSPS KAKENHI Grant Number 19K17126.