Department of Biomedical Engineering, Johns Hopkins School of Medicine, Baltimore, Maryland, USA.
Department of Radiation Oncology and Molecular Radiation Sciences, Johns Hopkins School of Medicine, Baltimore, Maryland, USA.
Med Phys. 2022 Jul;49(7):4794-4803. doi: 10.1002/mp.15665. Epub 2022 Apr 18.
Pancreatic cancer is the fourth leading cause of cancer-related death with a 10% 5-year overall survival rate (OS). Radiation therapy (RT) in addition to dose escalation improves the outcome by significantly increasing the OS at 2 and 3 years but is hindered by the toxicity of the duodenum. Our group showed that the insertion of hydrogel spacer reduces duodenal toxicity, but the complex anatomy and the demanding procedure make the benefits highly uncertain. Here, we investigated the feasibility of augmenting the workflow with intraoperative feedback to reduce the adverse effects of the uncertainties.
We simulated three scenarios of the virtual spacer for four cadavers with two types of gross tumor volume (GTV) (small and large); first, the ideal injection; second, the nonideal injection that incorporates common spacer placement uncertainties; and third, the corrective injection that uses the simulation result from nonideal injection and is designed to compensate for the effect of uncertainties. We considered two common uncertainties: (1) "Narrowing" is defined as the injection of smaller spacer volume than planned. (2) "Missing part" is defined as failure to inject spacer in the ascending section of the duodenum. A total of 32 stereotactic body radiation therapy (SBRT) plans (33 Gy in 5 fractions) were designed, for four cadavers, two GTV sizes, and two types of uncertainties. The preinjection scenario for each case was compared with three scenarios of virtual spacer placement from the dosimetric and geometric points of view.
We found that the overlapping PTV space with the duodenum is an informative quantity for determining the effective location of the spacer. The ideal spacer distribution reduced the duodenal V33Gy for small and large GTV to less than 0.3 and 0.1cc, from an average of 3.3cc, and 1.2cc for the preinjection scenario. However, spacer placement uncertainties reduced the efficacy of the spacer in sparing the duodenum (duodenal V33Gy: 1.3 and 0.4cc). The separation between duodenum and GTV decreased by an average of 5.3 and 4.6 mm. The corrective feedback can effectively bring back the expected benefits from the ideal location of the spacer (averaged V33Gy of 0.4 and 0.1cc).
An informative feedback metric was introduced and used to mitigate the effect of spacer placement uncertainties and maximize the benefits of the EUS-guided procedure.
胰腺癌是癌症相关死亡的第四大主要原因，其 5 年总生存率（OS）为 10%。放射治疗（RT）除了增加剂量外，还可以通过显著提高 2 年和 3 年的 OS 来改善预后，但这受到十二指肠毒性的限制。我们的研究小组表明，水凝胶间隔物的插入可降低十二指肠毒性，但由于复杂的解剖结构和苛刻的操作程序，其益处高度不确定。在这里，我们研究了通过术中反馈增强工作流程的可行性，以降低不确定性的不良影响。
我们使用四个尸体的两种类型的大体肿瘤体积（GTV）（小和大）模拟了虚拟间隔物的三种情况；首先是理想的注射；其次是非理想的注射，包括常见的间隔物放置不确定性；第三是使用非理想注射的模拟结果进行的校正注射，旨在补偿不确定性的影响。我们考虑了两种常见的不确定性：（1）“变窄”定义为注射的间隔物体积小于计划的体积。（2）“缺失部分”定义为未能在十二指肠升段注射间隔物。共设计了 32 个立体定向体部放射治疗（SBRT）计划（5 次分割，每次 33Gy），用于四个尸体、两种 GTV 大小和两种类型的不确定性。对于每个病例，在剂量学和几何角度比较了预注射方案与虚拟间隔物放置的三种方案。
我们发现，与十二指肠重叠的 PTV 空间是确定间隔物有效位置的一个信息量较大的指标。理想的间隔物分布将小 GTV 和大 GTV 的十二指肠 V33Gy 降低到小于 0.3cc 和 0.1cc，从预注射方案的平均 3.3cc 和 1.2cc。然而，间隔物放置的不确定性降低了间隔物保护十二指肠的效果（十二指肠 V33Gy：1.3cc 和 0.4cc）。十二指肠与 GTV 之间的距离平均减少了 5.3mm 和 4.6mm。校正反馈可以有效地从间隔物的理想位置带来预期的益处（平均 V33Gy 为 0.4cc 和 0.1cc）。
引入了一种信息反馈指标，用于减轻间隔物放置不确定性的影响，并最大限度地提高超声内镜引导下操作的益处。
