Abstract：
BACKGROUND: Using the pencil beam raster scanning method employed at most carbon beam treatment facilities, spots can be moved without interrupting the beam, allowing for the delivery of a dose between spots (move dose). This technique is also known as Dose-Driven-Continuous-Scanning (DDCS). To minimize its impact on HIMAK patient dosimetry, there\'s an upper limit to the move dose. Spots within a layer are grouped into sets, or \"break points,\" allowing continuous irradiation. The beam is turned off when transitioning between sets or at the end of a treatment layer or spill. The control system beam-off is accomplished by turning off the RF Knockout (RFKO) extraction and after a brief delay the High Speed Steering Magnet (HSST) redirects the beam transport away from isocenter to a beam dump.
OBJECTIVE: The influence of the move dose and beam on/off control on the dose distribution and irradiation time was evaluated by measurements never before reported and modelled for Hitachi Carbon DDCS.
METHODS: We conducted fixed-point and scanning irradiation experiments at three different energies, both with and without breakpoints. For fixed-point irradiation, we utilized a 2D array detector and an oscilloscope to measure beam intensity over time. The oscilloscope data enabled us to confirm beam-off and beam-on timing due to breakpoints, as well as the relative timing of the RFKO signal, HSST signal, and dose monitor (DM) signals. From these measurements, we analyzed and modelled the temporal characteristics of the beam intensity. We also developed a model for the spot shape and amplitude at isocenter occurring after the beam-off signal which we called flap dose and its dependence on beam intensity. In the case of scanning irradiation, we measured move doses using the 2D array detector and compared these measurements with our model.
RESULTS: We observed that the most dominant time variation of the beam intensity was at 1 kHz and its harmonic frequencies. Our findings revealed that the derived beam intensity cannot reach the preset beam intensity when each spot belongs to different breakpoints. The beam-off time due to breakpoints was approximately 100 ms, while the beam rise time and fall time (tdecay ) were remarkably fast, about 10 ms and 0.2 ms, respectively. Moreover, we measured the time lag (tdelay ) of approximately 0.2 ms between the RFKO and HSST signals. Since tdelay ≈ tdecay at HIMAK then the HSST is activated after the residual beam intensity, resulting in essentially zero flap dose at isocenter from the HSST. Our measurements of the move dose demonstrated excellent agreement with the modelled move dose.
CONCLUSIONS: We conducted the first move dose measurement for a Hitachi Carbon synchrotron, and our findings, considering beam on/off control details, indicate that Hitachi\'s carbon synchrotron provides a stable beam at HIMAK. Our work suggests that measuring both move dose and flap dose should be part of the commissioning process and possibly using our model in the Treatment Planning System (TPS) for new facilities with treatment delivery control systems with higher beam intensities and faster beam-off control.
OBJECTIVE: The influence of the move dose and beam on/off control on the dose distribution and irradiation time was evaluated by measurements never before reported and modelled for Hitachi Carbon DDCS.
METHODS: We conducted fixed-point and scanning irradiation experiments at three different energies, both with and without breakpoints. For fixed-point irradiation, we utilized a 2D array detector and an oscilloscope to measure beam intensity over time. The oscilloscope data enabled us to confirm beam-off and beam-on timing due to breakpoints, as well as the relative timing of the RFKO signal, HSST signal, and dose monitor (DM) signals. From these measurements, we analyzed and modelled the temporal characteristics of the beam intensity. We also developed a model for the spot shape and amplitude at isocenter occurring after the beam-off signal which we called flap dose and its dependence on beam intensity. In the case of scanning irradiation, we measured move doses using the 2D array detector and compared these measurements with our model.
RESULTS: We observed that the most dominant time variation of the beam intensity was at 1 kHz and its harmonic frequencies. Our findings revealed that the derived beam intensity cannot reach the preset beam intensity when each spot belongs to different breakpoints. The beam-off time due to breakpoints was approximately 100 ms, while the beam rise time and fall time (tdecay ) were remarkably fast, about 10 ms and 0.2 ms, respectively. Moreover, we measured the time lag (tdelay ) of approximately 0.2 ms between the RFKO and HSST signals. Since tdelay ≈ tdecay at HIMAK then the HSST is activated after the residual beam intensity, resulting in essentially zero flap dose at isocenter from the HSST. Our measurements of the move dose demonstrated excellent agreement with the modelled move dose.
CONCLUSIONS: We conducted the first move dose measurement for a Hitachi Carbon synchrotron, and our findings, considering beam on/off control details, indicate that Hitachi\'s carbon synchrotron provides a stable beam at HIMAK. Our work suggests that measuring both move dose and flap dose should be part of the commissioning process and possibly using our model in the Treatment Planning System (TPS) for new facilities with treatment delivery control systems with higher beam intensities and faster beam-off control.
摘要：
背景：使用在大多数碳束处理设施中采用的笔形束光栅扫描方法，斑点可以在不中断光束的情况下移动，允许在点之间递送剂量(移动剂量)。该技术也称为剂量驱动连续扫描(DDCS)。为了将其对HIMAK患者剂量测定的影响降至最低，移动剂量有一个上限。图层中的斑点被分组为集合，或“断点，“允许连续照射。当在组之间或在治疗层或溢出结束时转换时,关闭光束。控制系统的光束关闭是通过关闭RF敲除（RFKO）提取来实现的，并且在短暂的延迟之后，高速转向磁体（HSST）将光束传输从等中心重定向到光束收集器。
目的：移动剂量和光束开/关控制对剂量分布和辐照时间的影响是通过从未报道过的测量进行评估的，并为HitachiCarbonDDCS建模。
方法：我们在三种不同能量下进行了定点和扫描辐照实验，有和没有断点。对于定点辐照，我们利用二维阵列探测器和示波器来测量光束强度随时间的变化。示波器数据使我们能够确认由于断点而导致的波束关闭和波束打开时序，以及RFKO信号的相对时序，HSST信号,和剂量监测（DM）信号。从这些测量中，我们分析并建模了光束强度的时间特征。我们还开发了一个模型，用于在光束关闭信号之后发生的等中心点的光斑形状和振幅，我们将其称为襟翼剂量及其对光束强度的依赖性。在扫描照射的情况下，我们使用2D阵列检测器测量移动剂量，并将这些测量值与我们的模型进行比较。
结果：我们观察到光束强度的最主要时间变化是在1kHz及其谐波频率处。我们的发现表明，当每个光斑属于不同的断点时，得出的光束强度无法达到预设的光束强度。由于断点的光束关闭时间约为100毫秒，而光束上升时间和下降时间（tdecay）非常快，大约10ms和0.2ms，分别。此外，我们测量了RFKO和HSST信号之间大约0.2ms的时滞(tdelay)。由于在HIMAK处tdelay≈tdecay，因此在剩余光束强度之后激活HSST，导致HSST等中心处的皮瓣剂量基本上为零。我们对移动剂量的测量结果与建模的移动剂量非常吻合。
结论：我们对日立碳同步加速器进行了第一次移动剂量测量，和我们的发现,考虑光束开/关控制细节，表明日立的碳同步加速器在HIMAK提供稳定的光束。我们的工作表明，测量移动剂量和皮瓣剂量应该是调试过程的一部分，并可能在治疗计划系统（TPS）中使用我们的模型，用于具有更高光束强度和更快光束关闭控制的治疗输送控制系统的新设施。
目的：移动剂量和光束开/关控制对剂量分布和辐照时间的影响是通过从未报道过的测量进行评估的，并为HitachiCarbonDDCS建模。
方法：我们在三种不同能量下进行了定点和扫描辐照实验，有和没有断点。对于定点辐照，我们利用二维阵列探测器和示波器来测量光束强度随时间的变化。示波器数据使我们能够确认由于断点而导致的波束关闭和波束打开时序，以及RFKO信号的相对时序，HSST信号,和剂量监测（DM）信号。从这些测量中，我们分析并建模了光束强度的时间特征。我们还开发了一个模型，用于在光束关闭信号之后发生的等中心点的光斑形状和振幅，我们将其称为襟翼剂量及其对光束强度的依赖性。在扫描照射的情况下，我们使用2D阵列检测器测量移动剂量，并将这些测量值与我们的模型进行比较。
结果：我们观察到光束强度的最主要时间变化是在1kHz及其谐波频率处。我们的发现表明，当每个光斑属于不同的断点时，得出的光束强度无法达到预设的光束强度。由于断点的光束关闭时间约为100毫秒，而光束上升时间和下降时间（tdecay）非常快，大约10ms和0.2ms，分别。此外，我们测量了RFKO和HSST信号之间大约0.2ms的时滞(tdelay)。由于在HIMAK处tdelay≈tdecay，因此在剩余光束强度之后激活HSST，导致HSST等中心处的皮瓣剂量基本上为零。我们对移动剂量的测量结果与建模的移动剂量非常吻合。
结论：我们对日立碳同步加速器进行了第一次移动剂量测量，和我们的发现,考虑光束开/关控制细节，表明日立的碳同步加速器在HIMAK提供稳定的光束。我们的工作表明，测量移动剂量和皮瓣剂量应该是调试过程的一部分，并可能在治疗计划系统（TPS）中使用我们的模型，用于具有更高光束强度和更快光束关闭控制的治疗输送控制系统的新设施。
