Author(s): Johnston ML, Vial P, Wiltshire KL, Bell LJ, Blome S,
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Abstract AIM: To compare online position verification strategies with offline correction protocols for patients undergoing definitive prostate radiotherapy. MATERIALS AND METHODS: We analysed 50 patients with implanted fiducial markers undergoing curative prostate radiation treatment, all of whom underwent daily kilovoltage imaging using an on-board imager. For each treatment, patients were set-up initially with skin tattoos and in-room lasers. Orthogonal on-board imager images were acquired and the couch shift to match both bony anatomy and the fiducial markers recorded. The set-up error using skin tattoos and offline bone correction was compared with online bone correction. The fiducial markers were used as the reference. RESULTS: Data from 1923 fractions were analysed. The systematic error was ≤1 mm for all protocols. The average random error was 2-3mm for online bony correction and 3-5mm for skin tattoos or offline-bone. Online-bone showed a significant improvement compared with offline-bone in the number of patients with >5mm set-up errors for >10\% (P<0.001) and >20\% (P<0.003) of their fractions. CONCLUSIONS: Online correction to bony anatomy reduces both systematic and random set-up error in patients undergoing prostate radiotherapy, and is superior to offline correction methods for those patients not suitable for fiducial markers or daily soft-tissue imaging. Copyright © 2011 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.
This article was published in Clin Oncol (R Coll Radiol)
and referenced in Journal of Cancer Science & Therapy