IGRT strategies for pelvic lymph node irradiation in high-risk prostate cancer: motion and margins

Definition of margins to determine the optimal image-guided radiotherapy (IGRT) strategy for pelvic lymph node irradiation is essential in high-risk prostate cancer. In this work, these margins were derived from systematic and random motions measured using repeated CT scans in 19 patients, based on matching to either bony anatomy or prostate for a 3 or 6 degrees-of-freedom (DOF) couch. When matching to bony anatomy, margins were smaller for lymph nodes than when matching to prostate, but larger for prostate and seminal vesicles. The prostate and seminal vesicle margins were unchanged when using a 3 vs 6 DOF couch, but lymph node margins were smaller in the anterior-posterior direction.

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