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  • br New clinical target volume delineation for adjuvant radio

    2019-10-14


    2.3. “New” clinical target volume delineation for adjuvant radiotherapy
    With the aim of determining the smallest possible volume while encompassing the majority of local recurrences for adjuvant radio-therapy, the combined contour structure of the celiac artery and the superior mesenteric artery was expanded in six directions with multiple optimizations to create two clinical target volumes based on the three-dimensional local recurrence map: (1) clinical target volume encompassing 90% of all local failures (CTV-90); (2) clinical target volume encompassing 90% of the local failures of only the postoperative pancreatic head cancer (CTV-90 H). The expansion data of the two new target volumes were recorded.
    2.4. “New” target volume and standard RTOG 0848 target volume delineation in simulated cases
    Five patients with pancreatic head cancer after pancreaticoduo-denectomy were selected as simulated patients. Organs at risk, including the liver, stomach, kidneys, small intestine, large bowel and spinal cord, were delineated.
    First, each simulated case’s abdominal width and thickness at the central point of the celiac artery and superior mesenteric artery combined contour were measured. The above two expansion datasets were both translated into individual expansion datasets for each simulated case by scaling for the abdominal width and thickness between simulated patients and the template patient, thus generating CTV-90 and CTV-90 H for each simulated case. The planning target volume (PTV)-90 and PTV-90 H was created by expanding CTV-90 and CTV-90 H by 5 mm, respectively. Both PTV-90 and PTV-90 H should be edited to be adjacent to the liver
     if they protrude into this dose-limiting organ and then retracted to avoid the stomach, Ifenprodil hemitartrate and large bowel by 3 mm to generate PTV-90 edited and PTV-90 H edited.
    The Radiation Therapy Oncology Group consensus panel devel-oped guidelines for the delineation of the clinical target volume for the postoperative treatment of pancreatic head cancer [11].
    2.4.2.1. Region of interest delineation. Six regions of interest were delineated on the CT images of simulated patients as follows:
    • celiac artery: the most proximal 1 cm of the celiac artery from the origin of the aorta; • superior mesenteric artery: the most proximal 3 cm of the supe-rior mesenteric artery from the origin of the aorta; • portal vein: the portion of the portal vein located anteriorly and medially to the inferior vena cava until confluence with the supe-rior mesenteric vein or splenic vein;
    • Preoperative tumour volume or postoperative tumour bed: area occupied by the primary tumour on preoperative images; • pancreaticojejunostomy: identified by following the pancreatic remnant medially and anteriorly until the junction with the jeju-nal loop is noted;
    • aorta: the portion of the aorta from the top of the uppermost portal vein, celiac artery or superior mesenteric artery slice to the bottom of L2.
    2.4.2.2. Generation of the standard adjuvant field. The above six regions of interest were expanded as follows:
    • celiac artery, superior mesenteric artery and portal vein regions were expanded by 1.0 cm in all directions; • pancreaticojejunostomy and postoperative tumour bed regions were expanded by 0.5∼1.0 cm in all directions;
    • the aorta region was expanded by 2.5∼3.0 cm, 1.0 cm, 2.0∼2.5 cm and 0.2 cm on the right, left, anterior and posterior sides, respec-tively. The aorta region should be expanded up to the highest slice of the celiac artery, portal vein or pancreaticojejunostomy expansion.
    The above six region of interest expansions were merged into the CTV for postoperative adjuvant radiotherapy of pancreatic head cancer by addition options of Boolean logic operations. If the CTV protruded into the dose-limiting organs, such as the liver, stom-ach, small intestine and large bowel, it should be edited such that it would be adjacent to these normal structures to establish CTV edited. Then, the PTV edited was generated by expanding the CTV edited by 0.5 cm in all directions.