Mattei I, Bini F, Collamati F, De Lucia E, Frallicciardi P M, Iarocci E, Mancini-Terracciano C, Marafini M, Muraro S, Paramatti R, Patera V, Piersanti L, Pinci D, Rucinski A, Russomando A, Sarti A, Sciubba A, Solfaroli Camillocci E, Toppi M, Traini G, Voena C, Battistoni G
INFN-Sezione di Milano, Italy.
Phys Med Biol. 2017 Feb 21;62(4):1438-1455. doi: 10.1088/1361-6560/62/4/1438. Epub 2017 Jan 23.
Charged particle beams are used in particle therapy (PT) to treat oncological patients due to their selective dose deposition in tissues with respect to the photons and electrons used in conventional radiotherapy. Heavy (Z > 1) PT beams can additionally be exploited for their high biological effectiveness in killing cancer cells. Nowadays, protons and carbon ions are used in PT clinical routines. Recently, interest in the potential application of helium and oxygen beams has been growing. With respect to protons, such beams are characterized by their reduced multiple scattering inside the body, increased linear energy transfer, relative biological effectiveness and oxygen enhancement ratio. The precision of PT demands online dose monitoring techniques, crucial to improving the quality assurance of any treatment: possible patient mis-positioning and biological tissue changes with respect to the planning CT scan could negatively affect the outcome of the therapy. The beam range confined in the irradiated target can be monitored thanks to the neutral or charged secondary radiation emitted by the interactions of hadron beams with matter. Among these secondary products, prompt photons are produced by nuclear de-excitation processes, and at present, different dose monitoring and beam range verification techniques based on prompt-γ detection are being proposed. It is hence of importance to perform γ yield measurement in therapeutic-like conditions. In this paper we report on the yields of prompt photons produced by the interaction of helium, carbon and oxygen ion beams with a poly-methyl methacrylate (PMMA) beam stopping target. The measurements were performed at the Heidelberg Ion-Beam Therapy Center (HIT) with beams of different energies. An LYSO scintillator, placed at [Formula: see text] and [Formula: see text] with respect to the beam direction, was used as the photon detector. The obtained γ yields for the carbon ion beams are compared with results from the literature, while no other results from helium and oxygen beams have been published yet. A discussion on the expected resolution of a slit camera detector is presented, demonstrating the feasibility of a prompt-γ-based monitoring technique for PT treatments using helium, carbon and oxygen ion beams.
带电粒子束因其在组织中的剂量沉积相对于传统放射治疗中使用的光子和电子具有选择性，故而被用于粒子治疗（PT）以治疗肿瘤患者。重（Z > 1）PT束还因其在杀死癌细胞方面具有高生物有效性而得到额外利用。如今，质子和碳离子被用于PT临床常规治疗。最近，对氦离子束和氧离子束潜在应用的兴趣与日俱增。相对于质子，此类束的特点是在体内的多次散射减少、线能量转移增加、相对生物有效性和氧增强比提高。PT的精确性要求采用在线剂量监测技术，这对于提高任何治疗的质量保证至关重要：相对于计划CT扫描，患者可能的位置错误以及生物组织变化可能会对治疗结果产生负面影响。由于强子束与物质相互作用产生的中性或带电次级辐射，可以监测局限在受照射靶区内的束流射程。在这些次级产物中，瞬发光子由核退激过程产生，目前，基于瞬发γ探测的不同剂量监测和束流射程验证技术正在被提出。因此，在类似治疗的条件下进行γ产额测量非常重要。在本文中，我们报告了氦离子束、碳离子束和氧离子束与聚甲基丙烯酸甲酯（PMMA）束流阻挡靶相互作用产生的瞬发光子产额。测量是在海德堡离子束治疗中心（HIT）使用不同能量的束流进行的。一个LYSO闪烁体，相对于束流方向放置在[公式：见正文]和[公式：见正文]处，用作光子探测器。将获得的碳离子束γ产额与文献结果进行了比较，而氦离子束和氧离子束尚无其他已发表的结果。本文还讨论了狭缝相机探测器的预期分辨率，证明了基于瞬发γ的监测技术用于氦离子束、碳离子束和氧离子束PT治疗的可行性。
