MR simulation for prostate radiation therapy: effect of coil mounting position on image quality.

Objective:To eliminate the effects of body deformation for MR-based prostate treatment planning, coil mounts are essential. In this study, we evaluated the effect of the coil set-up on image quality.Methods:A custom-designed pelvic-shaped phantom was scanned by systematically increasing the anterior body-to-coil (BTC) distance from 30 to 90 mm. The image quality near the organs of interest was determined in order to characterize the relationship between image quality and BTC distance at the critical organ structures. The half intensity reduction (HIR) was calculated to determine the sensitivity of each organ structure to the BTC distance change.Results:As the BTC distance increased, the uniformity reduced at 3% per millimetre. The HIR value indicated that the bladder signal is most sensitive to the change in BTC distance. By maintaining a constant BTC distance set-up, the intensity uniformity was improved by 28% along the B0 directions.Conclusion:Positioning the MRI coil on mounts can reduce body deformat...