Significant changes of T2 value in the peripheral zone and seminal vesicles after ejaculation

Objectives To analyse the quantitative changes of the prostate and seminal vesicles (SV) on magnetic resonance imaging (MRI) after ejaculation. Methods Ten healthy young males were enrolled for T2-weighted and T2 mapping MRI before and after two consecutive ejaculations. T2 values of the peripheral zone (PZ) and the central gland (CG) at the midgland of the prostate were compared before and after ejaculation, respectively. T2 values of the PZ at the apex and base were also compared before and after, respectively. Pre- and post-ejaculation SV volumes were compared. The Wilcoxon’s signed rank test with Bonferroni adjustment was used for comparison. Results After ejaculation, T2 values of the PZ significantly decreased (mean, 119±20 vs. 105±21, p =0.002) while those of the CG did not significantly change at the midgland. At the apex, T2 values of the PZ also decreased significantly (mean, 114±9 vs. 94±7, p =0.002). On the other hand, T2 values of the PZ did not change at the base. SV volumes were significantly reduced after ejaculation (mean, 11.1±7.7mL vs. 7.2±6.7mL, p =0.002). Conclusions Ejaculation decreases T2 values of the PZ at the midgland and apex, and reduces SV volumes. Abstinence periods should be considered in evaluating the prostate and SV on MRI. Key points • T2 values decrease after ejaculation in the apical-mid peripheral zone. • Ejaculation does not affect T2 values of the central gland. • Volume of the seminal vesicles decreases after ejaculation. • An abstinence period should be considered before pelvic MRI in men.