Department of Radiation Oncology and Image-Applied Therapy, Kyoto University Graduate School of Medicine, Kyoto, Japan.
Int J Radiat Oncol Biol Phys. 2012 Apr 1;82(5):1619-26. doi: 10.1016/j.ijrobp.2011.01.050. Epub 2011 Apr 7.
To investigate the interfractional dose variations for intensity-modulated radiotherapy (RT) combined with breath-hold (BH) at end-exhalation (EE) for pancreatic cancer.
A total of 10 consecutive patients with pancreatic cancer were enrolled. Each patient was fixed in the supine position on an individualized vacuum pillow with both arms raised. Computed tomography (CT) scans were performed before RT, and three additional scans were performed during the course of chemoradiotherapy using a conventional RT technique. The CT data were acquired under EE-BH conditions (BH-CT) using a visual feedback technique. The intensity-modulated RT plan, which used five 15-MV coplanar ports, was designed on the initial BH-CT set with a prescription dose of 39 Gy at 2.6 Gy/fraction. After rigid image registration between the initial and subsequent BH-CT scans, the dose distributions were recalculated on the subsequent BH-CT images under the same conditions as in planning. Changes in the dose-volume metrics of the gross tumor volume (GTV), clinical target volume (CTV = GTV + 5 mm), stomach, and duodenum were evaluated.
For the GTV and clinical target volume (CTV), the 95th percentile of the interfractional variations in the maximal dose, mean dose, dose covering 95% volume of the region of structure, and percentage of the volume covered by the 90% isodose line were within ±3%. Although the volume covered by the 39 Gy isodose line for the stomach and duodenum did not exceed 0.1 mL at planning, the volume covered by the 39 Gy isodose line for these structures was up to 11.4 cm(3) and 1.8 cm(3), respectively.
Despite variations in the gastrointestinal state and abdominal wall position at EE, the GTV and CTV were mostly ensured at the planned dose, with the exception of 1 patient. Compared with the duodenum, large variations in the stomach volume receiving high-dose radiation were observed, which might be beyond the negligible range in achieving dose escalation with intensity-modulated RT combined with BH at EE.
研究在呼气末（EE）屏气（BH）下进行胰腺癌调强放疗（IMRT）的分次剂量变化。
共纳入 10 例连续的胰腺癌患者。每位患者均仰卧于个体化真空枕上，双臂抬高。在放疗前进行 CT 扫描，并在化疗放疗过程中使用常规放疗技术进行另外 3 次扫描。CT 数据是在 BH-CT 条件下（BH-CT）使用视觉反馈技术采集的。初始 BH-CT 组上设计了 5 个 15-MV 共面端口的调强放疗计划，处方剂量为 39 Gy，每次 2.6 Gy。在初始 BH-CT 扫描和后续 BH-CT 扫描之间进行刚性图像配准后，在相同条件下，根据后续 BH-CT 图像重新计算剂量分布。评估大体肿瘤体积（GTV）、临床靶区（CTV=GTV+5mm）、胃和十二指肠的剂量体积学指标的变化。
对于 GTV 和临床靶区（CTV），最大剂量、平均剂量、覆盖区域 95%体积的剂量、覆盖 90%等剂量线体积的百分比的 95%分位值的分次变化在±3%以内。虽然胃和十二指肠的 39 Gy 等剂量线所覆盖的体积在计划时未超过 0.1ml，但这些结构的 39 Gy 等剂量线所覆盖的体积分别高达 11.4cm3和 1.8cm3。
尽管在 EE 时胃肠道状态和腹壁位置存在变化，但 GTV 和 CTV 仍主要按计划剂量覆盖，只有 1 例患者除外。与十二指肠相比，胃体积接受高剂量辐射的变化较大，这可能超出了在 EE 下用调强放疗联合 BH 实现剂量递增的可忽略范围。
