J Radiat Res. 2022 Jan 20;63(1):137-147. doi: 10.1093/jrr/rrab098.
This study aimed to quantitatively clarify the baseline drift for each respiratory cycle in two respiratory-gating methods using the intra-beam respiratory motion data of lung cancer patients. The residual motion and dose distribution were calculated based on intra-beam respiratory motion data with the baseline drift. To quantify the baseline drift $\Delta$ during irradiation, it was defined as the inclination between the detected expiration point and the expiration point in the next cycle in the anterior-posterior (AP), cranial-caudal (CC) and left-right (LR) directions obtained using an in-house programme. The baseline drift value reached up to 0.74 mm/s in the CC direction as per the respiratory motion data of 10 patients. The homogeneity index (HI) of the phase-gating method tended to increase because the target was irradiated even when the amplitude position of the target differed from period to period. In contrast, the amplitude-gating method enabled irradiation considering the amplitude position of the target because the gating window was set considering the amplitude position of the respiratory motion. The respiratory-gating methods and respiratory phase in respiratory-gating lung stereotactic body radiation therapy (SBRT) must be determined based on the respiratory motion of the patients.
本研究旨在使用肺癌患者的射束内呼吸运动数据，定量阐明两种呼吸门控方法中每个呼吸周期的基线漂移。基于具有基线漂移的射束内呼吸运动数据计算残余运动和剂量分布。为了量化照射过程中的基线漂移 $\Delta$，我们使用内部程序，将检测到的呼气末点与下一个呼吸周期的呼气末点之间的倾斜度定义为前-后（AP）、颅-尾（CC）和左-右（LR）方向的倾斜度。根据 10 名患者的呼吸运动数据，CC 方向的基线漂移值高达 0.74mm/s。相控门控方法的均匀性指数（HI）趋于增加，因为即使目标的位置随时间变化，目标仍被照射。相比之下，由于考虑了呼吸运动的幅度位置设置了门控窗口，因此幅度门控方法可以考虑目标的幅度位置进行照射。呼吸门控立体定向体部放射治疗（SBRT）中的呼吸门控方法和呼吸相位必须基于患者的呼吸运动来确定。
