Our finding of prostate gland distortion Veliparib price with erMRI is consistent with previous studies. Heijmink et al. (35) found that introduction of an endorectal

coil reduced mean prostate volume by 17.9% compared with standard body array coil MRI, which is comparable to the 13% reduction seen in the present study. Those authors also found that the endorectal coil led to significantly shorter mean anterior-posterior diameter (5.38 mm), longer medial-lateral diameter (3.49 mm), and longer craniocaudal length (2.24 mm) (p < 0.05 for all comparisons); all of these findings are consistent with our results and with those from another study evaluating prostate distortion with erMRI (36). However, to the authors' knowledge, our study is the first to directly evaluate erMRI for prostate brachytherapy preplanning and compare it with other imaging modalities. From our analysis, we conclude that erMRI is not ideal for treatment planning, find more because the resulting anatomic distortion required nonstandard, often asymmetric loading patterns, and also often required needles

to track through the rectum to achieve adequate peripheral zone coverage. Given the susceptibility of brachytherapy treatment planning to minor changes in target delineation, the distortion in prostate volume and dimensions with the endorectal coil could result in major changes in the accuracy of dose delivery; because the prostate will return to its normal shape after the procedure, the erMRI-based plan does not accurately represent the anatomy that exists GNAT2 for the duration of treatment delivery. Notably, we used erMRI images for the present study that were obtained for the purpose of ruling out extraprostatic extension or seminal vesicle involvement, and were thus optimized

for this purpose. erMRI may be more useful for treatment planning if it was optimized for treatment planning, such as minimizing anatomic distortion by filling the balloon less, and this represents an interesting direction for future study. There are several important limitations to the present study that must be considered. For example, the retrospective nature of this study necessitated the use of scans acquired at different time points—preimplant TRUS and erMRI images were used along with sMRI images acquired 30 days postimplant. This introduces the possibility that postimplant edema could alter prostate volume and dimensions and thus affect treatment planning on the postimplant MRI. However, Crook et al. (37) demonstrated in a study of 241 patients that approximately 90% of postimplant edema resolves at 1 month, although some patients may experience prolonged edema. Further, we found no significant difference between the mean prostate volume using sMRI compared with TRUS (33.9 cm3 sMRI vs. 32.5 cm3 TRUS, p = 0.076).