br of ensuring accurate target coverage which
of ensuring accurate target coverage, which may have the potential of achieving dose escalation and increased local control.
2. Methods and materials
2.1. Study population
Clinical and computed tomography (CT) imaging data of 48 patients (35 males, 13 females) with local recurrence of pri-mary pancreatic head cancer and pancreatic body cancer who had undergone radical resection were collected from Taishan Medical University Affiliated Taishan Hospital, Shandong Medical Imaging Research Institute and Shandong Cancer Hospital between January 2014 and June 2017. Pancreatic cancer was diagnosed histopatho-logically for all patients; all patients had postoperative abdominal thin layer dynamic enhanced CT scan. Among them, 30 had pancre-atic head cancer, and 18 had pancreatic body cancer. The patients were aged 46 to 80 years, with an average of 62 years (mean age ± SD = 61.7 ± 8.4 years). A majority of patients with pancreatic head cancer had pancreaticoduodenectomy, and patients with pan-creatic body cancer correspondingly had distal pancreatectomy. Local recurrence was defined as soft tissue mass or nodule for-mation at the resection area or soft tissue wrapping around the blood vessels of the superior mesenteric artery and the celiac artery and progression of retroperitoneal Salvinorin A nodes. Patients with local recurrence combined with distant metastasis were included in the study, but not those who received palliative surgery or who had ampullary cancer.
2.2. Three-dimensional local recurrence map model
2.2.1. Coordinate data acquisition of recurrence foci
Patients’ CT image data were imported into the Varian EclipseTM 13.5 treatment planning system (TPS). The enhanced thin layer CT series was selected to create a new 2-mm-layer-thick three-dimensional image specialized for target volume contouring. Two radiotherapy oncologists determined the local recurrence position
and border after thoroughly reading the clinical and image data, and any disagreements were resolved by consensus. Then, the tumour recurrence foci were outlined, and the central point of each recur-rence foci was generated. Finally, recurrence was denoted using a dot by reference to the central point. The celiac artery and supe-rior mesenteric artery were each contoured from the origin of the aorta to 1 cm and 3 cm along the natural curve of the vessels infe-riorly. The celiac artery or superior mesenteric artery, whichever was closer to the recurrence, was chosen as the origin to obtain the coordinates of the recurrence dot in relation to these vessels after calculating the distance between the artery and the recur-rence foci in each patient. The abdominal width and thickness at the coordinate origin (the central point of the celiac artery or the superior mesenteric artery) were measured on the cross-section image considering individual physical differences.
2.2.2. Generation of the local recurrence map
The celiac artery and the superior mesenteric artery were con-toured as described above on the 2-mm-layer-thick CT scan of a patient after pancreaticoduodenectomy of a primary pancreatic cancer as the template image, and three abdominal widths and thicknesses at the central points of the celiac artery, the superior mesenteric artery and the combined contour, respectively, were measured. Then, the abdominal width and thickness at the central point of the celiac artery and superior mesenteric artery combined contour were defined as the standards.
All the recurrence dots that had been scaled by the ratio of the abdominal width and thickness between the template and the indi-vidual patients were eventually marked on the template image, and the three-dimensional local recurrence map of patients with resected pancreatic head cancer and pancreatic body cancer was generated by digital reconstruction of the template image.