title: A randomised trial of patient repositioning during radiotherapy using a megavoltage imaging system.
abstract: Effectiveness of radiotherapy is dependent on the accuracy of beam alignment. Recent developments in megavoltage imaging allow real-time monitoring of beam placement. Maximum gains from this new technology can only be made if the information is utilised to correct patient positioning prospectively before the majority of a treatment fraction is delivered. We have developed and utilised an integrated megavoltage imaging system to perform a randomised trial demonstrating significant improvements in accuracy using treatment intervention techniques for pelvic radiotherapy. The mean field-placement accuracy improved from 4.3 mm to 2 mm and the proportion of treatments given with a field-placement error of > or = 5 mm decreased from 69% to 7%. This improvement in accuracy may enable smaller margins around the target volume to be chosen whilst ensuring complete target coverage at each treatment fraction.
authors.affiliation: Radiotherapy Unit, Royal Marsden Hospital, Sutton, Surrey, UK.
authors.forename: J
authors.initials: J
authors.lastname: Gildersleve
authors.forename: D P
authors.initials: DP
authors.lastname: Dearnaley
authors.forename: P M
authors.initials: PM
authors.lastname: Evans
authors.forename: M
authors.initials: M
authors.lastname: Law
authors.forename: C
authors.initials: C
authors.lastname: Rawlings
authors.forename: W
authors.initials: W
authors.lastname: Swindell
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011471:Prostatic Neoplasms / Q000532:radiotherapy*; D011880:Radiotherapy Planning, Computer-Assisted; D011882:Radiotherapy, High-Energy; D015203:Reproducibility of Results; D016896:Treatment Outcome; D001749:Urinary Bladder Neoplasms / Q000532:radiotherapy*