MR Imaging of the Prostate and Adjacent Anatomic Structures before, during, and after Ejaculation: Qualitative and Quantitative Evaluation

Abstract

Purpose To determine the possibility of obtaining high-quality magnetic resonance (MR) images before, during, and immediately after ejaculation and detecting measurable changes in quantitative MR imaging parameters after ejaculation. Materials and Methods In this prospective, institutional review board–approved, HIPAA-compliant study, eight young healthy volunteers (median age, 22.5 years), after providing informed consent, underwent MR imaging while masturbating to the point of ejaculation. A 1.5-T MR imaging unit was used, with an eight-channel surface coil and a dynamic single-shot fast spin-echo sequence. In addition, a quantitative MR imaging protocol that allowed calculation of T1, T2, and apparent diffusion coefficient (ADC) values was applied before and after ejaculation. Volumes of the prostate and seminal vesicles (SV) were calculated by using whole-volume segmentation on T2-weighted images, both before and after ejaculation. Pre- and postejaculation changes in quantitative MR parameters and measured volumes were evaluated by using the Wilcoxon signed rank test with Bonferroni adjustment. Results There was no significant change in prostate volumes on pre- and postejaculation images, while the SV contracted by 41% on average (median, 44.5%; P = .004). No changes before and after ejaculation were observed in T1 values or in T2 and ADC values in the central gland, while T2 and ADC values were significantly reduced in the peripheral zone by 12% and 14%, respectively (median, 13% and 14.5%, respectively; P = .004). Conclusion Successful dynamic MR imaging of ejaculation events and the ability to visualize internal sphincter closure, passage of ejaculate, and significant changes in SV volumes were demonstrated. Significant changes in peripheral zone T2 and ADC values were observed.

The longitudinal effect of ejaculation on seminal vesicle fluid volume and whole-prostate ADC as measured on prostate MRI

“…It should be noted that although seminal vesicle fluid makes up 40–85% of the ejaculate [ 15 ], there is also a contribution from the prostate gland (15–30%), testis (<5%) and bulbourethral glands (1–5%); thus, ejaculate volume alone may not provide an accurate indication of changes in seminal vesicle volume. Early work using vesiculography [ 16 ] and ultrasound [ 17 , 18 ] and subsequently confirmed by a more recent MRI study [ 9 ] showed 30–40% reductions in seminal vesicle volume immediately post-ejaculation. However, these studies are not representative of an outpatient MR patient population.…”

“…Only one prospective MRI study has documented volume change in this context, demonstrating a 41% mean reduction in SV volume immediately post-ejaculation [ 9 ]. Scanning at this time point is not representative of a clinical MRI study and it is in fact possible that seminal vesicle fluid replacement may occur relatively quickly.…”

The association between seminal vesicle size and duration of abstinence from ejaculation

“…A recent study analysing prostate and SV size found that SV volume decreased by approximately 40% immediately after ejaculation. However, this study examined only pre-ejaculation and immediate post-ejaculation SV volume (Medved et al, 2014). In our study, size as a function of abstinence period between ejaculations is examined, which has not previously been reported.…”

Practical aspects of prostate MRI: hardware and software considerations, protocols, and patient preparation

“…The validity of this claim, however, has not been tested. In a pilot study, Medved et al reported decreased signal intensity on T2-weighted imaging and the apparent diffusion coefficient maps in the peripheral zone after ejaculation, possibly reflecting a reduction in the volume of ejaculatory fluid within the gland [163]. The authors did not observe any dramatic differences in image quality or significant changes in prostate volume after ejaculation.…”