(2) Lateral fields (LAT): Anterior border, symphysis pubis posterior border, S2-S3 interspace. Vessel contours were hidden, and conventional pelvic fields were outlined: (1) anterior/posterior fields (AP): superior border, L5-S1 interspace inferior border, obturator foramina lateral border, 2 centimeters lateral to pelvic brim. Methods and Materials: Pelvic arteries were contoured on non-contrast-enhanced CT simulation images of 43 patients with cervix cancer, FIGO Stages I-III. Purpose: To assess the adequacy of nodal coverage of 'conventional' pelvic radiation fields for carcinoma of the cervix, with contoured pelvic vessels on simulation computed tomography (CT) as surrogates for lymph node location. On the basis of these findings, recommended guidelines including a detailed pelvic LN contouring atlas have been produced and implemented in the PIVOTAL trial. Because the RMH technique is supported by phase 1 and 2 trial safety data, we proposed modifications to the RTOG technique, including the addition of a 3-mm BEM, which resulted in LN-CTV coverage similar to that of the RMH technique, with reduction in bowel and planning target volume overlap. Conclusions: Vascular expansion techniques result in larger LN-CTVs than the freehand RMH technique. Evaluation of conformity between LN-CTVs from each technique revealed similar volumes and coverage. The mean volume of bowel within the planning target volume was 146.9 cm seen using the RMH technique. The nodal coverage was 56%, 76%, 88%, 94%, and 99% using vessel margins of 3, 5, 7, 10, and 15 mm, respectively. Results: In total, 1216 nodal contours were evaluated. The volume of normal tissue within each clinical target volume and planning target volume was also measured to aid selection of the margin that could provide maximal nodal, but minimal normal tissue, coverage. The nodal contours were then overlaid and individual nodes analyzed for coverage. Five clinical target volumes were generated for each patient using modified margins of 3, 5, 7, 10, and 15 mm around the iliac vessels. Methods and Materials: Twenty patients with gynecologic malignancies underwent magnetic resonance imaging with administration of iron oxide particles. Purpose: To establish guidelines for delineating the clinical target volume for pelvic nodal irradiation by mapping the location of lymph nodes in relation to the pelvic anatomy.
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