PDF(Pubmed)
Abstract：
UNASSIGNED: The total time of radiation treatment delivery for pancreatic cancer patients with daily online adaptive radiation therapy (ART) on an MR-Linac can range from 50 to 90 min. During this period, the target and normal tissues undergo changes due to respiration and physiologic organ motion. We evaluated the dosimetric impact of the intrafraction physiological organ changes.
UNASSIGNED: Ten locally advanced pancreatic cancer patients were treated with 50 Gy in five fractions with intensity-modulated respiratory-gated radiation therapy on a 0.35-T MR-Linac. Patients received both pre- and post-treatment volumetric MRIs for each fraction. Gastrointestinal organs at risk (GI-OARs) were delineated on the pre-treatment MRI during the online ART process and retrospectively on the post-treatment MRI. The treated dose distribution for each adaptive plan was assessed on the post-treatment anatomy. Prescribed dose volume histogram metrics for the scheduled plan on the pre-treatment anatomy, the adapted plan on the pre-treatment anatomy, and the adapted plan on post-treatment anatomy were compared to the OAR-defined criteria for adaptation: the volume of the GI-OAR receiving greater than 33 Gy (V33Gy) should be ≤1 cubic centimeter.
UNASSIGNED: Across the 50 adapted plans for the 10 patients studied, 70% were adapted to meet the duodenum constraint, 74% for the stomach, 12% for the colon, and 48% for the small bowel. Owing to intrafraction organ motion, at the time of post-treatment imaging, the adaptive criteria were exceeded for the duodenum in 62% of fractions, the stomach in 36%, the colon in 10%, and the small bowel in 48%. Compared to the scheduled plan, the post-treatment plans showed a decrease in the V33Gy, demonstrating the benefit of plan adaptation for 66% of the fractions for the duodenum, 95% for the stomach, 100% for the colon, and 79% for the small bowel.
UNASSIGNED: Post-treatment images demonstrated that over the course of the adaptive plan generation and delivery, the GI-OARs moved from their isotoxic low-dose region and nearer to the dose-escalated high-dose region, exceeding dose-volume constraints. Intrafraction motion can have a significant dosimetric impact; therefore, measures to mitigate this motion are needed. Despite consistent intrafraction motion, plan adaptation still provides a dosimetric benefit.
UNASSIGNED: Ten locally advanced pancreatic cancer patients were treated with 50 Gy in five fractions with intensity-modulated respiratory-gated radiation therapy on a 0.35-T MR-Linac. Patients received both pre- and post-treatment volumetric MRIs for each fraction. Gastrointestinal organs at risk (GI-OARs) were delineated on the pre-treatment MRI during the online ART process and retrospectively on the post-treatment MRI. The treated dose distribution for each adaptive plan was assessed on the post-treatment anatomy. Prescribed dose volume histogram metrics for the scheduled plan on the pre-treatment anatomy, the adapted plan on the pre-treatment anatomy, and the adapted plan on post-treatment anatomy were compared to the OAR-defined criteria for adaptation: the volume of the GI-OAR receiving greater than 33 Gy (V33Gy) should be ≤1 cubic centimeter.
UNASSIGNED: Across the 50 adapted plans for the 10 patients studied, 70% were adapted to meet the duodenum constraint, 74% for the stomach, 12% for the colon, and 48% for the small bowel. Owing to intrafraction organ motion, at the time of post-treatment imaging, the adaptive criteria were exceeded for the duodenum in 62% of fractions, the stomach in 36%, the colon in 10%, and the small bowel in 48%. Compared to the scheduled plan, the post-treatment plans showed a decrease in the V33Gy, demonstrating the benefit of plan adaptation for 66% of the fractions for the duodenum, 95% for the stomach, 100% for the colon, and 79% for the small bowel.
UNASSIGNED: Post-treatment images demonstrated that over the course of the adaptive plan generation and delivery, the GI-OARs moved from their isotoxic low-dose region and nearer to the dose-escalated high-dose region, exceeding dose-volume constraints. Intrafraction motion can have a significant dosimetric impact; therefore, measures to mitigate this motion are needed. Despite consistent intrafraction motion, plan adaptation still provides a dosimetric benefit.
摘要：
■在MR-Linac上进行每日在线适应性放射治疗（ART）的胰腺癌患者的放射治疗总时间范围为50至90分钟。在此期间,目标组织和正常组织由于呼吸和生理器官运动而发生变化。我们评估了内部生理器官变化的剂量学影响。
■10例局部晚期胰腺癌患者在0.35-TMR-Linac上接受5个部分的50Gy调强呼吸门控放射治疗。对于每个部分,患者接受治疗前和治疗后的体积MRI。在在线ART过程中，在治疗前MRI上描绘了胃肠道危险器官（GI-OAR），并在治疗后MRI上进行了回顾性描述。在治疗后解剖结构上评估每个适应性计划的治疗剂量分布。针对治疗前解剖结构上的计划计划的规定剂量体积直方图度量，关于治疗前解剖结构的适应性计划，将治疗后解剖结构的适应计划与OAR定义的适应标准进行了比较：接受大于33Gy（V33Gy）的GI-OAR的体积应≤1立方厘米。
■在研究的10名患者的50个调整计划中，70%的人适应了十二指肠的限制，74%为胃，结肠12%，小肠占48%。由于内部器官运动，在治疗后成像时，十二指肠在62%的部分中超过了适应性标准，36％的胃，10%的结肠，小肠占48%。与预定计划相比，治疗后的计划显示V33Gy下降，证明计划适应十二指肠66％的部分的好处，95%的胃，100%的结肠，小肠占79%。
■后处理图像表明，在自适应计划的生成和交付过程中，GI-OAR从其等氧低剂量区域移动到更靠近剂量递增的高剂量区域，超过剂量体积限制。帧内运动会产生显著的剂量测定影响；因此，需要采取措施减轻这种运动。尽管一致的内部运动，计划适应仍然提供剂量测定的好处。
■10例局部晚期胰腺癌患者在0.35-TMR-Linac上接受5个部分的50Gy调强呼吸门控放射治疗。对于每个部分,患者接受治疗前和治疗后的体积MRI。在在线ART过程中，在治疗前MRI上描绘了胃肠道危险器官（GI-OAR），并在治疗后MRI上进行了回顾性描述。在治疗后解剖结构上评估每个适应性计划的治疗剂量分布。针对治疗前解剖结构上的计划计划的规定剂量体积直方图度量，关于治疗前解剖结构的适应性计划，将治疗后解剖结构的适应计划与OAR定义的适应标准进行了比较：接受大于33Gy（V33Gy）的GI-OAR的体积应≤1立方厘米。
■在研究的10名患者的50个调整计划中，70%的人适应了十二指肠的限制，74%为胃，结肠12%，小肠占48%。由于内部器官运动，在治疗后成像时，十二指肠在62%的部分中超过了适应性标准，36％的胃，10%的结肠，小肠占48%。与预定计划相比，治疗后的计划显示V33Gy下降，证明计划适应十二指肠66％的部分的好处，95%的胃，100%的结肠，小肠占79%。
■后处理图像表明，在自适应计划的生成和交付过程中，GI-OAR从其等氧低剂量区域移动到更靠近剂量递增的高剂量区域，超过剂量体积限制。帧内运动会产生显著的剂量测定影响；因此，需要采取措施减轻这种运动。尽管一致的内部运动，计划适应仍然提供剂量测定的好处。
