Alam Sadegh, Veeraraghavan Harini, Tringale Kathryn, Amoateng Emmanuel, Subashi Ergys, Wu Abraham J, Crane Christopher H, Tyagi Neelam
Department of Medical Physics, Memorial Sloan-Kettering Cancer Center, New York, NY 10065, USA.
Department of Radiation Oncology, Memorial Sloan-Kettering Cancer Center, New York, NY 10065, USA.
Phys Imaging Radiat Oncol. 2022 Feb 17;21:54-61. doi: 10.1016/j.phro.2022.02.007. eCollection 2022 Jan.
Stereotactic body radiation therapy (SBRT) of locally advanced pancreatic cancer (LAPC) is challenging due to significant motion of gastrointestinal (GI) organs. The goal of our study was to quantify inter and intrafraction deformations and dose accumulation of upper GI organs in LAPC patients.
Five LAPC patients undergoing five-fraction magnetic resonance-guided radiation therapy (MRgRT) using abdominal compression and daily online plan adaptation to 50 Gy were analyzed. A pre-treatment, verification, and post-treatment MR imaging (MRI) for each of the five fractions (75 total) were used to calculate intra and interfraction motion. The MRIs were registered using Large Deformation Diffeomorphic Metric Mapping (LDDMM) deformable image registration (DIR) method and total dose delivered to stomach_duodenum, small bowel (SB) and large bowel (LB) were accumulated. Deformations were quantified using gradient magnitude and Jacobian integral of the Deformation Vector Fields (DVF). Registration DVFs were geometrically assessed using Dice and 95th percentile Hausdorff distance (HD95) between the deformed and physician's contours. Accumulated doses were then calculated from the DVFs.
Median Dice and HD95 were: Stomach_duodenum (0.9, 1.0 mm), SB (0.9, 3.6 mm), and LB (0.9, 2.0 mm). Median (max) interfraction deformation for stomach_duodenum, SB and LB was 6.4 (25.8) mm, 7.9 (40.5) mm and 7.6 (35.9) mm. Median intrafraction deformation was 5.5 (22.6) mm, 8.2 (37.8) mm and 7.2 (26.5) mm. Accumulated doses for two patients exceeded institutional constraints for stomach_duodenum, one of whom experienced Grade1 acute and late abdominal toxicity.
LDDMM method indicates feasibility to measure large GI motion and accumulate dose. Further validation on larger cohort will allow quantitative dose accumulation to more reliably optimize online MRgRT.
由于胃肠道（GI）器官的显著运动，局部晚期胰腺癌（LAPC）的立体定向体部放射治疗（SBRT）具有挑战性。我们研究的目的是量化LAPC患者上消化道器官的分次间和分次内变形以及剂量累积情况。
分析了5例接受五分次磁共振引导放射治疗（MRgRT）的LAPC患者，采用腹部压迫并每日在线计划调整至50 Gy。使用五个分次（共75次）中每次的治疗前、验证和治疗后磁共振成像（MRI）来计算分次间和分次内运动。使用大变形微分同胚度量映射（LDDMM）可变形图像配准（DIR）方法对MRI进行配准，并累积输送到胃十二指肠、小肠（SB）和大肠（LB）的总剂量。使用变形矢量场（DVF）的梯度幅度和雅可比积分对变形进行量化。使用变形轮廓与医生轮廓之间的骰子系数和第95百分位数豪斯多夫距离（HD95）对配准DVF进行几何评估。然后根据DVF计算累积剂量。
骰子系数和HD95的中位数分别为：胃十二指肠（0.9，1.0 mm）、小肠（0.9，3.6 mm）和大肠（0.9，2.0 mm）。胃十二指肠、小肠和大肠的分次间变形中位数（最大值）分别为6.4（25.8）mm、7.9（40.5）mm和7.6（35.9）mm。分次内变形中位数分别为5.5（22.6）mm、8.2（37.8）mm和7.2（26.5）mm。两名患者的累积剂量超过了胃十二指肠的机构限制，其中一名患者出现了1级急性和晚期腹部毒性。
LDDMM方法表明测量胃肠道大运动和累积剂量是可行的。在更大队列上的进一步验证将使定量剂量累积能够更可靠地优化在线MRgRT。
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