Department of Medical Physics, Memorial Sloan Kettering Cancer Center, New York, New York, USA.
Department of Radiation Oncology, Memorial Sloan Kettering Cancer Center, New York, New York, USA.
J Appl Clin Med Phys. 2022 Nov;23(11):e13740. doi: 10.1002/acm2.13740. Epub 2022 Jul 30.
Beam gating with deep inspiration breath hold (DIBH) usually depends on some external surrogate to infer internal target movement, and the exact internal movement is unknown. In this study, we tracked internal targets and characterized residual motion during DIBH treatment, guided by a surface imaging system, for gastrointestinal cancer. We also report statistics on treatment time.
We included 14 gastrointestinal cancer patients treated with surface imaging-guided DIBH volumetrically modulated arc therapy, each with at least one radiopaque marker implanted near or within the target. They were treated in 25, 15, or 10 fractions. Thirteen patients received treatment for pancreatic cancer, and one underwent separate treatments for two liver metastases. The surface imaging system monitored a three-dimensional surface with ± 3 mm translation and ± 3° rotation threshold. During delivery, a kilovolt image was automatically taken every 20° or 40° gantry rotation, and the internal marker was identified from the image. The displacement and residual motion of the markers were calculated. To analyze the treatment efficiency, the treatment time of each fraction was obtained from the imaging and treatment timestamps in the record and verify system.
Although the external surface was monitored and limited to ± 3 mm and ± 3°, significant residual internal target movement was observed in some patients. The range of residual motion was 3-21 mm. The average displacement for this cohort was 0-3 mm. In 19% of the analyzed images, the magnitude of the instantaneous displacement was > 5 mm. The mean treatment time was 17 min with a standard deviation of 4 min.
Precaution is needed when applying surface image guidance for gastrointestinal cancer treatment. Using it as a solo DIBH technique is discouraged when the correlation between internal anatomy and patient surface is limited. Real-time radiographic verification is critical for safe treatments.
采用深吸气屏气（DIBH）的射束门控技术通常依赖于一些外部替代物来推断内部靶区运动，而内部靶区的实际运动情况尚不清楚。本研究采用体表成像系统引导胃肠道肿瘤患者进行 DIBH 容积调强弧形治疗，对内部靶区进行跟踪并分析 DIBH 治疗期间的残余运动情况，同时报告了治疗时间的统计学数据。
我们纳入了 14 例接受体表成像引导 DIBH 容积调强弧形治疗的胃肠道肿瘤患者，每位患者在靶区附近或内部均植入至少一个不透射线标记物。这些患者的治疗分割数为 25、15 或 10 次。13 例患者接受胰腺癌治疗，1 例患者同时接受了两个肝转移灶的单独治疗。体表成像系统监测三维体表的平移和旋转，平移范围为±3mm，旋转范围为±3°。治疗过程中，每 20°或 40°机架旋转自动拍摄千伏级图像，并从图像中识别内部标记物。计算标记物的位移和残余运动。为了分析治疗效率，从记录和验证系统中的成像和治疗时间戳中获取每个分割的治疗时间。
尽管外部体表受到监测，限制在±3mm 和±3°以内，但在一些患者中仍观察到明显的内部靶区残余运动。残余运动的范围为 3-21mm。本队列的平均位移为 0-3mm。在分析的 19%的图像中，瞬时位移幅度>5mm。平均治疗时间为 17min，标准差为 4min。
在胃肠道肿瘤的治疗中应用体表图像引导时需要谨慎。当内部解剖结构与患者体表的相关性有限时，不鼓励将其单独作为 DIBH 技术应用。实时放射影像验证对于安全治疗至关重要。
