Accuracy of prostate measurements on MRI with and without an endorectal coil.

Purpose: To assess accuracy of prostate measurements with and without endorectal coil (ERC).

Materials And Methods: Anteroposterior (AP), transverse (TX) and craniocaudal (CC) measurements were recorded from 49 prostate magnetic resonance images (MRIs) done both with and without ERC. Prostate weight was calculated as follows: AP*TX*CC*π/6. Prostate dimensions and weight were obtained from radical prostatectomy pathology report.

Results: After ERC placement, AP decreased by 0.71 cm [95% confidence interval (CI) 0.80-0.61], TX and CC increased by 0.26 cm (95% CI 0.18-0.33) and 0.25 cm (95% CI 0.16-0.35), respectively. Agreement between weight on pathology and MR was excellent: intraclass correlation coefficient (ICC) without ERC=0.96, ICC with ERC=0.90.

Conclusion: Although ERC distorts measurements and despite a tendency to underestimate the prostate weight, absolute agreement between prostate weight on pathology and MRI is excellent, both with and without ERC.