title: Computer-assisted, atlas-based segmentation for target volume delineation in whole pelvic IMRT for prostate cancer.
abstract: The purpose of this study is to evaluate whether computer-assisted segmentation is clinically feasible in target volume delineation for prostate cancer patients treated with whole pelvic IMRT. An atlas was created, comprised of 44 clinically node-negative prostate cancer patients. Three regions of interest (ROIs) were chosen for analysis: prostate, pelvic lymph nodes, and rectum. For a separate tester set of 15 patients with previously contoured ROIs by three experienced physicians, atlas-assisted contours were compared to manual contours by calculating a volumetric overlap index. In the tester set patients, the average overlap between the manually drawn and atlas-based contours for the prostate, pelvic lymph nodes, and rectum was 60%, 51%, and 64%, respectively. The volume differences were significant in the rectum and pelvic lymph nodes (p = 0.049 and p = 0.016, respectively); this was not true for the prostate. A subset analysis based on physician-specific atlases showed that the average overlap index for the pelvic lymph nodal volume increased from 51% to 60%, while the other ROIs had no significant changes. Despite significant inter-physician differences, atlas-based segmentation for pelvic lymph node delineation serves as an initial guideline for physicians, potentially improving both consistency and efficiency in contouring.
authors.affiliation: Department of Radiation Oncology, University of California, San Francisco, San Francisco, CA, USA.
authors.forename: Sunanda
authors.initials: S
authors.lastname: Pejavar
authors.forename: Sue S
authors.initials: SS
authors.lastname: Yom
authors.forename: Andrew
authors.initials: A
authors.lastname: Hwang
authors.forename: Joycelyn
authors.initials: J
authors.lastname: Speight
authors.forename: Alexander
authors.initials: A
authors.lastname: Gottschalk
authors.forename: I-Chow
authors.initials: IC
authors.lastname: Hsu
authors.forename: Mack
authors.initials: M
authors.lastname: Roach
authors.forename: Ping
authors.initials: P
authors.lastname: Xia
mesh_terms: D000230:Adenocarcinoma / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy*; D006801:Humans; D008198:Lymph Nodes / Q000473:pathology; D008297:Male; D010388:Pelvis / Q000000981:diagnostic imaging / Q000473:pathology; D011467:Prostate / Q000000981:diagnostic imaging / Q000473:pathology; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy*; D011880:Radiotherapy Planning, Computer-Assisted; D050397:Radiotherapy, Intensity-Modulated; D012007:Rectum / Q000000981:diagnostic imaging / Q000473:pathology; D014057:Tomography, X-Ray Computed