Figure 2.

Case 1: Target volume creation (internal GTV, clinical target volume, and organ at risk) and planning volume creation (planning target volume and PRV). (A, B) The internal GTV (red) defines the complete extent of the tumor, accounting for motion throughout the respiratory cycle. In escalated-dose fractionated radiation, the clinical target volume (yellow) comprises a 10-mm uniform expansion from the GTV and areas at risk of microscopic extension and may be further expanded to provide comprehensive, elective nodal irradiation around the celiac axis and superior mesenteric artery. The duodenum (black), small bowel (orange), large bowel (blue), stomach (purple), liver (teal), common bile duct (magenta), and spleen (cyan) are contoured as organs-at-risk. Of note, the bowel structures are contoured on all respiratory gated scans and are referred to as iBowel (small and large), iDuodenum, and iStomach. (C, D) A collective PRV structure is created as a 5-mm expansion from all bowel structures (gastrointestinal PRV) (orange). For hypofractionated, escalated-dose radiation therapy, 2 planning treatment volumes will be constructed. The PTV_Low (blue) is intended to comprehensively cover, with margin, the complete extent of the tumor, areas of possible microscopic extension, and elective nodal basins; therefore, the dose will be lower to this volume (3750 cGy in 15 fractions) with a uniform, unmodified, 5-mm expansion. The zPTV_High (green) will encompass the planning volume for dose-escalation (6750 cGy in 15 fractions); thus, this planning target volume will have no expansion and will consist of subtracting the gastrointestinal PRV from the internal GTV. Note: The patient’s pancreatic stent migrated into the bowel and was in the large bowel by the time of simulation. She passed it without complications. This emphasizes that stents may not be reliable for daily setup for radiation. Abbreviations: GTV = gross tumor volume; PRV = planning organ-at-risk volume.