Centre for Medical Radiation Physics, University of Wollongong, NSW, Australia.
Australian Nuclear Science and Technology Organisation, Lucas Heights, NSW, Australia.
Phys Med. 2019 Jun;62:20-32. doi: 10.1016/j.ejmp.2019.04.023. Epub 2019 May 6.
In this paper we investigate the emission and detection characteristics of prompt gamma (PG) rays for in vivo range verification during hadron therapy, using Geant4 simulations. Proton, He and C beams of varying energy are incident on water phantoms. The PG production yield, energy spectral characteristics and spatial correlation with the Bragg Peak (BP) have been quantified. Further, the angular distributions for PG detection with respect to a point-of-reference on the phantom surface have been explored. The temporal properties of PG emission and time-of-flight (TOF) of PG detection have also been investigated in correlation with the changing particle beam range. Our results show that the primary PG rays from nuclear interactions of the primary beam exhibit the closest correlation to the beam range but its signal is significantly masked by the concurrent secondary PG rays, particularly for heavier ions such as carbon ion beams. The PG TOF spectroscopy encodes the essential information of the beam range but requires high time resolution measurements to retrieve it. A hybrid PG detection system to utilize the energy, timing and spatial characteristics of PG rays is desirable for BP tracking in real-time.
本文使用 Geant4 模拟研究了用于重离子治疗中体内射程验证的瞬发伽马（PG）射线的发射和探测特性。质子、氦和碳束以不同的能量入射到水幻体上。定量研究了 PG 的产生产额、能谱特征以及与布拉格峰（BP）的空间相关性。此外，还研究了相对于幻体表面参考点的 PG 探测的角分布。还研究了 PG 发射的时间特性和 PG 探测的飞行时间（TOF）与变化的粒子束射程的相关性。我们的结果表明，来自初级束核相互作用的主要 PG 射线与束射程表现出最密切的相关性，但由于同时产生的次级 PG 射线，特别是对于较重的离子，如碳离子束，其信号被显著掩盖。PG-TOF 光谱学编码了束射程的基本信息，但需要高时间分辨率的测量才能恢复它。对于实时 BP 跟踪，需要一种利用 PG 射线的能量、时间和空间特性的混合 PG 检测系统。
