Kawabata Toru, Sugimoto Satoru, Kurokawa Chie, Usui Keisuke, Inoue Tatsuya, Nagata Hironori, Watanabe Hiroyuki, Sasai Keisuke
Juntendo Iji Zasshi. 2022 Nov 18;68(6):590-598. doi: 10.14789/jmj.JMJ22-0014-OA. eCollection 2022.
To develop a method for detecting jaw positions during jaw-tracking delivery to ensure an accurate delivery of radiation to patients using an electronic portal imaging device (EPID) in the cine mode on a linear accelerator for radiotherapy.
A bidirectional picket fence (BPF) plan was used in a novel application to detect jaw positions during jaw-tracking delivery. In the BPF plan, jaws tracked multileaf collimator (MLC) apertures. The irradiated patterns were acquired by an EPID in the cine mode.
The upper- and lower-half leaves in the MLC moved in opposite directions to facilitate detection of jaw positions on EPID images. A picket-fence-like image was created by summing all acquired cine images and evaluated to detect MLC leaf positions.
Jaw positions determined on the cine images were compared with those expected from the delivered BPF plan. The absolute differences (average ± 1 standard deviation) were 0.16 ± 0.19 mm for the X1 jaw and 0.11 ± 0.16 mm for the X2 jaw. The maximum error in the MLC leaf positions detected in the picket-fence-like pattern were 0.11 mm.
Jaw positions during jaw-tracking delivery were identified using the cine EPID images and could be determined within an accuracy better than 0.5 mm. The BPF plan is also available as a picket fence test and can determine the MLC leaf positions to an accuracy better than 0.5 mm.
开发一种在颌骨跟踪放疗过程中检测颌骨位置的方法，以确保在直线加速器上使用电子射野影像装置（EPID）的电影模式向患者准确输送辐射。
双向栅栏（BPF）计划被用于一种新颖的应用中，以在颌骨跟踪放疗过程中检测颌骨位置。在BPF计划中，颌骨跟踪多叶准直器（MLC）的孔径。通过EPID的电影模式获取照射图案。
MLC中的上半部分和下半部分叶片向相反方向移动，以便于在EPID图像上检测颌骨位置。通过对所有采集的电影图像求和创建一个类似栅栏的图像，并对其进行评估以检测MLC叶片位置。
将电影图像上确定的颌骨位置与所输送的BPF计划预期的位置进行比较。X1颌骨的绝对差值（平均值±1标准差）为0.16±0.19毫米，X2颌骨为0.11±0.16毫米。在类似栅栏的图案中检测到的MLC叶片位置的最大误差为0.11毫米。
使用电影EPID图像识别颌骨跟踪放疗过程中的颌骨位置，其确定精度优于0.5毫米。BPF计划也可作为栅栏测试使用，并且可以将MLC叶片位置确定到优于0.5毫米的精度。
