Technical Note: Range verification of pulsed proton beams from fixed‐field alternating gradient accelerator by means of time‐of‐flight measurement of ionoacoustic waves
Technical Note: Range verification of pulsed proton beams from fixed‐field alternating gradient accelerator by means of time‐of‐flight measurement of ionoacoustic waves
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技术资料：通过离子声波的飞行时间测量来验证来自固定场交变梯度加速器的脉冲质子束的范围
DOI：
10.1002/mp.15060
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发表时间：
2021
期刊：
影响因子：
3.8
通讯作者：
Matsuura Taeko
中科院分区：
文献类型：
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作者：
Nakamura Yuta;Takayanagi Taisuke;Uesaka Tomoki;Unlu Mehmet Burcin;Kuriyama Yasutoshi;Ishi Yoshihiro;Uesugi Tomonori;Kobayashi Masanori;Kudo Nobuki;Tanaka Sodai;Umegaki Kikuo;Tomioka Satoshi;Matsuura Taeko
目的离子声学是验证质子治疗中射束范围的有前途的方法之一。然而，波信号的弱点仍然是其临床应用的主要障碍。在这里，我们研究了固定场交变梯度加速器（FFA）的潜在用途，它是未来质子治疗的候选加速器之一。为此，使用模拟和实验程序评估了 FFA 短脉冲束实现的压力波幅度和距离精度。方法将来自 FFA 的 100 MeV 质子束穿过丙烯酸壁施加在水模型上。布拉格峰 (BP) 电离室 (BPC) 测量的光束范围为 77.6 毫米，而 BP 处的最大剂量估计为 0.35 戈瑞/脉冲。水听器放置在 BP 下游 20 毫米处，信号经过数字示波器放大和存储、平均和低通滤波。分析飞行时间 (TOF) 和两个相对 TOF 值以确定光束范围。此外，还进行了声波传输模拟来估计压力波的振幅。结果使用两个相对 TOF 计算的范围分别为 78.16 ± 0.01 和 78.14 ± 0.01 mm，这两个值与 BPC 测量的范围一致（差异为 0.5-0.6 mm）。相比之下，使用直接 TOF 会导致 1.8 毫米的距离误差。需要五倍和 50 倍平均值才能将 TOF 和相对 TOF 测量的范围变化分别抑制到 1 毫米以下。模拟表明探测器处的压力波幅度超过 7 帕斯卡。 结论 在使用相对 TOF 的临床能量下，来自 FFA 的约 21 ns 的脉冲光束获得了亚毫米范围精度。为了通过单次 TOF 测量精确量化范围，需要对测量系统进行后续改进。
PurposeIonoacoustics is one of the promising approaches to verify the beam range in proton therapy. However, the weakness of the wave signal remains a main hindrance to its application in clinics. Here we studied the potential use of a fixed‐field alternating gradient accelerator (FFA), one of the accelerator candidates for future proton therapy. For such end, magnitude of the pressure wave and range accuracy achieved by the short‐pulsed beam of FFA were assessed, using both simulation and experimental procedure.MethodsA 100 MeV proton beam from the FFA was applied on a water phantom, through the acrylic wall. The beam range measured by the Bragg peak (BP)‐ionization chamber (BPC) was 77.6 mm, while the maximum dose at BP was estimated to be 0.35 Gy/pulse. A hydrophone was placed 20 mm downstream of the BP, and signals were amplified and stored by a digital oscilloscope, averaged, and low‐pass filtered. Time‐of‐flight (TOF) and two relative TOF values were analyzed in order to determine the beam range. Furthermore, an acoustic wave transport simulation was conducted to estimate the amplitude of the pressure waves.ResultsThe range calculated when using two relative TOF was 78.16 ± 0.01 and 78.14 ± 0.01 mm, respectively, both values being coherent with the range measured by the BPC (the difference was 0.5‒0.6 mm). In contrast, utilizing the direct TOF resulted in a range error of 1.8 mm. Fivefold and 50‐fold averaging were required to suppress the range variation to below 1 mm for TOF and relative TOF measures, respectively. The simulation suggested the magnitude of pressure wave at the detector exceeded 7 Pascal.ConclusionA submillimeter range accuracy was attained with a pulsed beam of about 21 ns from an FFA, at a clinical energy using relative TOF. To precisely quantify the range with a single TOF measurement, subsequent improvement in the measuring system is required.