MRI-DTI Assessment of Urethral Internal Sphincter Ring and Prostate Base Morphology

An Observational Study of the Relationship Between the Urethral Internal Sphincter Ring and Prostate Base Morphology Using MRI-DTI Fiber Tracking

This is a single-center, observational imaging study designed to evaluate the in vivo morphology of the male urethral internal sphincter ring using magnetic resonance diffusion tensor imaging (MRI-DTI) fiber tracking and to investigate its relationship with prostate base morphology.

Male participants undergoing clinically indicated pelvic, seminal vesicle, or prostate-related MRI-DTI examinations will be included. The study population may include patients with benign prostatic enlargement, younger men undergoing MRI for suspected cryptorchidism or suspected seminal vesiculitis, and patients with prostate cancer scheduled to receive androgen deprivation therapy (ADT). All participants will undergo T2-weighted imaging and DTI. T2WI-DTI image registration, dual-region-of-interest fiber tracking, and three-dimensional reconstruction will be used to visualize ring-like muscle fiber structures in the bladder neck, prostate base, and proximal urethral region.

The cross-sectional imaging cohort will be used to assess the associations between prostate-side morphological parameters, including prostate volume, prostate base diameter or area, and intravesical prostatic protrusion, and sphincter-ring parameters, including ring inner diameter and ring area. The ADT paired cohort will undergo MRI-DTI before treatment and during follow-up after ADT to evaluate whether reduction in prostate volume and prostate base morphology is accompanied by corresponding changes in the urethral internal sphincter ring.

This study will not alter the participants' existing clinical diagnostic or treatment pathways. Imaging data will be analyzed using standardized post-processing and quantitative measurement procedures. The results may provide in vivo imaging evidence for age- and prostate-related displacement and morphological remodeling of the male urethral internal sphincter and may inform future surgical strategies for identifying, preserving, or reconstructing proximal urinary continence-related structures.

Study Overview

• Status: Not yet recruiting
• Conditions: Benign Prostatic Hyperplasia; Prostate Cancer; Urethral Internal Sphincter Morphology

Detailed Description

This is a single-center, observational imaging study designed to evaluate the in vivo morphology of the male urethral internal sphincter ring using magnetic resonance diffusion tensor imaging (MRI-DTI) fiber tracking, and to investigate the relationship between sphincter-ring morphology and prostate base morphology.

Post-prostatectomy urinary incontinence remains an important functional complication affecting quality of life in male patients. Although bladder neck preservation and continence-related reconstructive techniques are widely used in prostate surgery, direct in vivo imaging evidence demonstrating whether these approaches preserve or reconstruct the urethral internal sphincter remains limited. Conventional anatomical descriptions generally place the male internal sphincter in the bladder neck and proximal urethral region. However, clinical observations suggest that in men with prostate enlargement, protrusion of the prostate base, or marked changes in the bladder outlet region, a clearly defined ring-like smooth muscle structure may not be identifiable at the bladder neck. This raises the possibility that the location and morphology of the internal sphincter may change in association with prostate growth and remodeling of the prostate base.

MRI-DTI is an imaging technique that uses directional water diffusion to infer tissue fiber orientation and to reconstruct local fiber trajectories. In this study, DTI fiber tracking will be combined with T2-weighted imaging to visualize ring-like muscle fiber structures in the bladder neck, prostate base, and proximal urethral region. T2-weighted imaging will provide anatomical reference for the prostate, bladder neck, and proximal urethra, while DTI data will be used for fiber tracking and three-dimensional reconstruction of the urethral internal sphincter ring.

The study will include male participants undergoing clinically indicated pelvic, seminal vesicle, or prostate-related MRI-DTI examinations. The cross-sectional imaging cohort will include a broad range of male participants rather than only patients with benign prostatic hyperplasia. This cohort may include younger men undergoing MRI for suspected cryptorchidism or suspected seminal vesiculitis, as well as older men with benign prostatic enlargement or prostate base enlargement. This design is intended to capture a wider spectrum of prostate size, prostate base morphology, and urethral internal sphincter-ring morphology. A separate paired follow-up cohort will include patients with prostate cancer scheduled to receive androgen deprivation therapy (ADT), with MRI-DTI performed before treatment and during follow-up after ADT.

All imaging data will be processed using a standardized post-processing workflow. T2-weighted images and DTI datasets will be co-registered. The bladder neck, prostate base, and proximal urethral region will be identified on fused T2WI-DTI images. Two elliptical regions of interest will be placed anterior and posterior to the urethral region, and fiber tracts passing through both regions of interest will be selected to reconstruct the target ring-like fiber structure. The fused images will be used for quantitative measurements, and three-dimensional fiber models will be used for morphological visualization and representative case demonstration.

The main prostate-side morphological parameters will include prostate volume, intravesical prostatic protrusion, prostate base diameter, and prostate base area when technically feasible. Prostate volume will be calculated from T2-weighted images using standard three-dimensional measurements and an ellipsoid formula. Intravesical prostatic protrusion will be measured on sagittal T2-weighted images. Prostate base diameter and area will be measured at predefined anatomical levels based on the bladder neck and prostate base. The main sphincter-ring parameters will include the inner diameter and area of the urethral internal sphincter ring. Exploratory DTI-derived parameters, such as fractional anisotropy and mean diffusivity, may be recorded when the reconstructed fiber structure is technically stable and measurable.

In the cross-sectional cohort, the primary analysis will evaluate the association between prostate base morphology and urethral internal sphincter-ring morphology. Correlations will be assessed between prostate volume, prostate base diameter, prostate base area, intravesical prostatic protrusion, and sphincter-ring inner diameter or area. This analysis is intended to determine whether prostate enlargement or local remodeling of the prostate base is associated with expansion, displacement, or morphological remodeling of the internal sphincter ring.

In the ADT paired cohort, imaging parameters will be compared before and after androgen deprivation therapy. Changes in prostate volume, prostate base diameter, prostate base area, intravesical prostatic protrusion, and sphincter-ring diameter or area will be calculated. The study will further evaluate whether reduction in prostate volume and prostate base morphology after ADT is accompanied by corresponding changes in the urethral internal sphincter ring. Change values and percentage changes will be used to assess the relationship between prostate regression and sphincter-ring remodeling.

This study will not assign treatment or alter the participants' existing clinical diagnostic or therapeutic pathways. Imaging examinations will be performed in participants who undergo MRI for clinical indications or planned follow-up. The study will focus on image post-processing, quantitative measurement, and statistical analysis of MRI-DTI data. Participants with neurological bladder dysfunction, prior pelvic radiotherapy, prior urethral reconstruction or sphincter surgery, contraindications to MRI, or inadequate image quality for sphincter-ring assessment will be excluded.

Continuous variables will be summarized according to their distribution. Normality will be assessed using appropriate statistical tests and visual inspection when applicable. Correlations between prostate-side and sphincter-ring parameters will be evaluated using Pearson or Spearman correlation analysis according to data distribution. In the ADT cohort, paired comparisons will be performed using paired t-tests or Wilcoxon signed-rank tests as appropriate. Associations between changes in prostate morphology and changes in sphincter-ring morphology will also be assessed using correlation analysis. A two-sided P value of less than 0.05 will be considered statistically significant.

The study is expected to provide in vivo imaging evidence regarding the relationship between prostate base morphology and urethral internal sphincter-ring morphology. The findings may improve understanding of age- and prostate-related displacement and remodeling of the male internal sphincter and may provide imaging support for future surgical strategies aimed at identifying, preserving, or reconstructing proximal urinary continence-related structures during prostate surgery.

• Study Type: Observational
• Enrollment (Estimated): 80

Contacts and Locations

Study Locations

• China
  • Jiangsu
    • Taizhou, Jiangsu, China
      • JiangsuTaizhouPH

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Child; Adult; Older Adult
• Accepts Healthy Volunteers: No

• Sampling Method: Non-Probability Sample

Study Population

The study population will consist of male participants undergoing clinically indicated pelvic, seminal vesicle, or prostate-related MRI-DTI examinations at the study center. The cross-sectional imaging cohort will include a broad spectrum of male participants, including younger men undergoing MRI for suspected cryptorchidism or suspected seminal vesiculitis, as well as middle-aged and older men with benign prostatic enlargement or prostate base morphological changes. This cohort will be used to evaluate the relationship between prostate base morphology and urethral internal sphincter ring morphology.

A separate paired follow-up cohort will include patients with prostate cancer who are scheduled to receive androgen deprivation therapy. These participants will undergo MRI-DTI before treatment and during follow-up after ADT to assess whether changes in prostate volume and prostate base morphology are accompanied by corresponding changes in the urethral internal sphincter ring.

Description

Inclusion Criteria:

1. Male participants undergoing clinically indicated pelvic, seminal vesicle, or prostate-related MRI-DTI examination.
2. Participants with adequate T2-weighted MRI and DTI data for post-processing and quantitative assessment of the bladder neck, prostate base, and proximal urethral region.
3. Participants in the cross-sectional imaging cohort may include men undergoing MRI for suspected cryptorchidism, suspected seminal vesiculitis, benign prostatic enlargement, or other clinically indicated pelvic or prostate-related evaluations.
4. Participants in the ADT paired follow-up cohort must have prostate cancer and be scheduled to receive androgen deprivation therapy, with MRI-DTI planned before treatment and during follow-up after ADT.
5. Participants must be able to comply with MRI examination procedures.
6. Written informed consent will be obtained when required by the approved study protocol.

Exclusion Criteria:

1. Contraindications to MRI, including but not limited to incompatible metallic implants, severe claustrophobia, or other conditions preventing MRI examination.
2. Known neurogenic bladder dysfunction, including spinal cord injury, multiple sclerosis, Parkinson disease, or other neurological disorders that may significantly affect lower urinary tract function.
3. History of pelvic radiotherapy.
4. History of urethral reconstruction, sphincter surgery, or other prior surgery that substantially alters the bladder neck, proximal urethra, or prostate base anatomy.
5. Severe cardiopulmonary dysfunction, cognitive impairment, psychiatric disorder, or other conditions preventing cooperation with MRI examination or study procedures.
6. Use of medications or treatments within the previous 3 months that may substantially affect neuromuscular function of the lower urinary tract, as judged by the investigators.
7. Poor image quality or failed post-processing that prevents reliable visualization or measurement of the urethral internal sphincter ring.

Study Plan

How is the study designed?

Number of groups / cohorts

2

Cohorts and Interventions

Group / Cohort
Cross-sectional MRI-DTI Cohort; Male participants undergoing clinically indicated pelvic, seminal vesicle, or prostate-related MRI-DTI examinations, including younger men and men with prostate enlargement, will be evaluated cross-sectionally to assess the relationship between prostate base morphology and urethral internal sphincter ring morphology.
ADT Paired Follow-up Cohort; Patients with prostate cancer scheduled to receive androgen deprivation therapy will undergo MRI-DTI before treatment and during follow-up after ADT to evaluate whether changes in prostate base morphology are accompanied by corresponding changes in the urethral internal sphincter ring.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Urethral Internal Sphincter Ring Inner Diameter Measured by MRI-DTI Fiber Tracking	The inner diameter of the reconstructed urethral internal sphincter ring will be measured on fused T2-weighted MRI and DTI images. The measurement will be reported in millimeters.	At baseline MRI for the cross-sectional cohort; at baseline and 3 to 6 months after initiation of ADT for the paired follow-up cohort
Urethral Internal Sphincter Ring Area Measured by MRI-DTI Fiber Tracking	The area of the reconstructed urethral internal sphincter ring will be measured on fused T2-weighted MRI and DTI images. The measurement will be reported in square millimeters.	At baseline MRI for the cross-sectional cohort; at baseline and 3 to 6 months after initiation of ADT for the paired follow-up cohort

Secondary Outcome Measures

Outcome Measure	Time Frame
Prostate Base Diameter Measured on T2-Weighted MRI	At baseline MRI for the cross-sectional cohort; at baseline and 3 to 6 months after initiation of ADT for the paired follow-up cohort
Prostate Base Area Measured on T2-Weighted MRI	At baseline MRI for the cross-sectional cohort; at baseline and 3 to 6 months after initiation of ADT for the paired follow-up cohort
Intravesical Prostatic Protrusion Measured on Sagittal T2-Weighted MRI	At baseline MRI for the cross-sectional cohort; at baseline and 3 to 6 months after initiation of ADT for the paired follow-up cohort
Prostate Volume Calculated From T2-Weighted MRI	At baseline MRI for the cross-sectional cohort; at baseline and 3 to 6 months after initiation of ADT for the paired follow-up cohort

Other Outcome Measures

Outcome Measure	Time Frame
Change From Baseline in Urethral Internal Sphincter Ring Inner Diameter After ADT	Baseline and 3 to 6 months after initiation of ADT
Change From Baseline in Urethral Internal Sphincter Ring Area After ADT	Baseline and 3 to 6 months after initiation of ADT
Change From Baseline in Prostate Volume After ADT	Baseline and 3 to 6 months after initiation of ADT

Collaborators and Investigators

• Sponsor: Jiangsu Taizhou People's Hospital

Publications and helpful links

General Publications

• Hotker AM, Mazaheri Y, Zheng J, Moskowitz CS, Berkowitz J, Lantos JE, Pei X, Zelefsky MJ, Hricak H, Akin O. Prostate Cancer: assessing the effects of androgen-deprivation therapy using quantitative diffusion-weighted and dynamic contrast-enhanced MRI. Eur Radiol. 2015 Sep;25(9):2665-72. doi: 10.1007/s00330-015-3688-1. Epub 2015 Mar 29.
• Xu Z, Zhao J, Guan Z, Guo M, Bian H, Li Z, Zhao W, Liang S, Liu Y, Zhang S, Wang J. Internal urethral sphincter reconstruction with anterior bladder neck tube for robotic and laparoscopic radical prostatectomy: improving early return of continence. Transl Androl Urol. 2024 Jun 30;13(6):994-1003. doi: 10.21037/tau-23-583. Epub 2024 Jun 26.
• Mason M, Maldonado Pijoan X, Steidle C, Guerif S, Wiegel T, van der Meulen E, Bergqvist PB, Khoo V. Neoadjuvant androgen deprivation therapy for prostate volume reduction, lower urinary tract symptom relief and quality of life improvement in men with intermediate- to high-risk prostate cancer: a randomised non-inferiority trial of degarelix versus goserelin plus bicalutamide. Clin Oncol (R Coll Radiol). 2013 Mar;25(3):190-6. doi: 10.1016/j.clon.2012.09.010. Epub 2012 Dec 17.
• Hikita K, Honda M, Teraoka S, Nishikawa R, Kimura Y, Tsounapi P, Iwamoto H, Morizane S, Takenaka A. Intravesical prostatic protrusion may affect early postoperative continence undergoing robot-assisted radical prostatectomy. BMC Urol. 2020 Oct 21;20(1):164. doi: 10.1186/s12894-020-00740-0.
• Verde ASC, Santinha J, Carrasquinha E, Loucao N, Gaivao A, Fonseca J, Matos C, Papanikolaou N. Diffusion tensor-based fiber tracking of the male urethral sphincter complex in patients undergoing radical prostatectomy: a feasibility study. Insights Imaging. 2020 Nov 27;11(1):126. doi: 10.1186/s13244-020-00927-x.
• Sinha S, Sinha U, Malis V, Bhargava V, Sakamoto K, Rajasekaran M. Exploration of male urethral sphincter complex using diffusion tensor imaging (DTI)-based fiber-tracking. J Magn Reson Imaging. 2018 Oct;48(4):1002-1011. doi: 10.1002/jmri.26017. Epub 2018 Mar 23.
• Koraitim MM. The male urethral sphincter complex revisited: an anatomical concept and its physiological correlate. J Urol. 2008 May;179(5):1683-9. doi: 10.1016/j.juro.2008.01.010. Epub 2008 Mar 17.
• Kim JW, Kim DK, Ahn HK, Jung HD, Lee JY, Cho KS. Effect of Bladder Neck Preservation on Long-Term Urinary Continence after Robot-Assisted Laparoscopic Prostatectomy: A Systematic Review and Meta-Analysis. J Clin Med. 2019 Nov 24;8(12):2068. doi: 10.3390/jcm8122068.

Study record dates

Study Major Dates

• Study Start (Estimated): July 15, 2026
• Primary Completion (Estimated): August 1, 2027
• Study Completion (Estimated): June 1, 2028

Study Registration Dates

• First Submitted: July 6, 2026
• First Submitted That Met QC Criteria: July 6, 2026
• First Posted (Actual): July 10, 2026

Study Record Updates

• Last Update Posted (Actual): July 10, 2026
• Last Update Submitted That Met QC Criteria: July 6, 2026
• Last Verified: July 1, 2026

More Information

Terms related to this study

• Keywords: Prostate Cancer; Diffusion Tensor Imaging; Urethral Internal Sphincter
• Additional Relevant MeSH Terms: Urogenital Diseases; Genital Diseases; Genital Neoplasms, Male; Urogenital Neoplasms; Neoplasms by Site; Neoplasms; Genital Diseases, Male; Prostatic Diseases; Male Urogenital Diseases; Prostatic Neoplasms; Prostatic Hyperplasia
• Other Study ID Numbers: LSKY 2026-048-01

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No