Mizuno Hideyuki, Saito Osami, Tajiri Minoru, Kimura Taku, Kuroiwa Daigo, Shirai Toshiyuki, Inaniwa Taku, Fukahori Mai, Miki Kentaro, Fukuda Shigekazu
National institute of Radiological Sciences, QST, Chiba, Japan.
Hiroshima University Hospital, Hiroshima, Japan.
J Appl Clin Med Phys. 2019 Jan;20(1):37-42. doi: 10.1002/acm2.12463. Epub 2018 Nov 1.
This study reports the commissioning methodology and results of a respiratory gating system [AZ - 733 V/733 VI (Anzai Medical Co., Japan)] using a pressure sensor in carbon-ion scanning radiotherapy. Commissioning includes choosing a location and method for pressure sensor installation, delay time measurement of the system, and the final flow test. Additionally, we proposed a methodology for the determination of a threshold level of generating an on/off gate for the beam to the respiratory waveform, which is important for clinical application. Regarding the location and method for installation of the pressure sensor, the actual person's abdomen, back of the body position, and supine/prone positioning were checked. By comparing the motion between the pressure sensor output and the reference LED sensor motion, the chest rear surface was shown to be unsuitable for the sensor installation, due to noise in the signal caused by the cardiac beat. Regarding delay time measurement of the system, measurements were performed for the following four steps: (a). Actual motion to wave signal generation; (b). Wave signal to gate signal generation; (c). Gate signal to beam on/off signal generation; (d). Beam on/off signal to the beam irradiation. The total delay time measured was 46 ms (beam on)/33 ms (beam off); these were within the prescribed tolerance time (<100 ms). Regarding the final flow test, an end-to-end test was performed with a patient verification system using an actual carbon-ion beam; the respiratory gating irradiation was successfully performed, in accordance with the intended timing. Finally, regarding the method for determining the threshold level of the gate generation of the respiration waveform, the target motion obtained from 4D-CT was assumed to be correlated with the waveform obtained from the pressure sensor; it was used to determine the threshold value in amplitude direction.
本研究报告了在碳离子扫描放射治疗中使用压力传感器的呼吸门控系统[AZ - 733 V/733 VI（日本安zai医疗公司）]的调试方法和结果。调试包括选择压力传感器的安装位置和方法、系统延迟时间测量以及最终的流程测试。此外，我们提出了一种确定针对呼吸波形生成束流开/关门控的阈值水平的方法，这对于临床应用很重要。关于压力传感器的安装位置和方法，检查了实际人体的腹部、身体背部位置以及仰卧/俯卧位。通过比较压力传感器输出与参考LED传感器运动之间的运动情况，发现由于心跳引起的信号噪声，胸部后表面不适合安装传感器。关于系统延迟时间测量，对以下四个步骤进行了测量：(a). 实际运动到波形信号生成；(b). 波形信号到门控信号生成；(c). 门控信号到束流开/关信号生成；(d). 束流开/关信号到束流照射。测得的总延迟时间为46毫秒（束流开启）/33毫秒（束流关闭）；这些都在规定的容差时间内（<100毫秒）。关于最终的流程测试，使用实际碳离子束通过患者验证系统进行了端到端测试；呼吸门控照射按照预期时间成功进行。最后，关于确定呼吸波形门控生成阈值水平的方法，假设从4D-CT获得的目标运动与从压力传感器获得的波形相关；它被用于在幅度方向上确定阈值。
