A randomized comparison of interfraction and intrafraction prostate motion with and without abdominal compression.

摘要

BACKGROUND AND PURPOSE: To quantify inter- and intrafraction prostate motion in a standard VacLok (VL) immobilization device or in the BodyFix (BF) system incorporating a compression element which may reduce abdominal movement. MATERIALS AND METHODS: Thirty-two patients were randomly assigned to VL or BF. Interfraction prostate motion 3mm was corrected pre-treatment. EPIs were taken daily at the start and end of the first and last treatment beams. Interfraction and intrafraction prostate motion were measured for centre of mass (COM) and individual markers. RESULTS: There were no significant differences in interfraction (p0.002) or intrafraction (p0.16) prostate motion with or without abdominal compression. Median intrafraction motion was slightly smaller than interfraction motion in the AP (7.0mm vs. 7.6mm) and SI direction (3.2mm vs. 4.7mm). The final image captured the maximal intrafraction displacement in only 40% of fractions. Our PTV incorporated 95% of total prostate motion. CONCLUSIONS: Intrafraction motion became the major source of error during radiotherapy after online correction of interfraction prostate motion. The addition of 120mbar abdominal compression to custom pelvic immobilization influenced neither interfraction nor intrafraction prostate motion.