2060

Evaluation of urethral sphincter complex after LRP based on 3.0T pelvic floor magnetic resonance imaging combined with DTI and fiber tractography
Zhiheng Zhao1, Yingyu Che1, Jing Zhang1, Yue Wu1, Zitao Yang1, Qinyong Zhang1, Qingwei Wang1, Yifeng Sheng1, Ruilin Fan1, and Jingliang Cheng1
1the First Affiliated Hospital of Zhengzhou University, Zhengzhou, China

Synopsis

Keywords: Prostate, Diffusion Tensor Imaging, Radical prostatectomy; Urethral sphincters complex; Urinary incontinence

The anatomical-morphological and functional characteristics of the urethral sphincter complex, a key structure in the mechanism of urinary continence, have been studied mostly based on cadaveric dissection or animal experiments. In this study,we qualitatively and quantitatively evaluated the morphology and function of the urethral sphincter complex in patients after laparoscopic radical prostatectomy (LRP) using pelvic floor MRI combined with DTI and fiber tractography, and to investigate the anatomical factors affecting PPI.

Purpose

This study aimed to qualitatively and quantitatively analyze the morphology and function of the urethral sphincter complex in patients after laparoscopic radical prostatectomy (LRP) using pelvic floor MRI combined with diffusion tensor imaging (DTI) and fiber tractography, and to investigate the anatomical factors affecting postprostatectomy incontinence (PPI).

Methods

This prospective study included 38 patients who underwent LRP for prostate cancer, the patients were divided into urinary continence group (n=21) and urinary incontinence group (n=17). Membranous urethral length (MUL) and membranous urethral thickness (MUT) were measured on pelvic sagittal and axial T2 weighted images respectively. Fiber tractography of each analyzed structure of the urethral sphincter complex was performed. DTI-derived metrics, including fractional anisotropy (FA), apparent diffusion coefficient (ADC) and the three eigenvalues (λ1, λ2, λ3) were calculated. And the correlations between FA and ADC values of two-group urethral sphincter complex and the score of International Consultation Incontinence Questionnaire-Short Form (ICIQ-SF) were evaluated.

Results

Regarding pelvic MRI parameters, both preoperative and postoperative urinary continence groups had greater MUL than in the incontinence group, while the differences of MUT was not significant. As for DTI-derived metrics, the proximal and distal sphincters of postoperative patients showed significant decrease in FA value, increase in ADC value and the three eigenvalues, and FA values of the proximal sphincter and intermediate longitudinal muscle were higher in the urinary continence group compared to the incontinence group. In addition, the ICIQ-SF score was negatively correlated with FA value of proximal sphincter in continence group and with FA value of intermediate longitudinal muscle in incontinence group.

Conclusions

Pelvic floor MRI combined with DTI and fiber tractography is an effective and reliable non-invasive tool to assess the urethral sphincter complex. We found that the anatomical injury of proximal sphincter and intermediate longitudinal muscle is an important factor leading to the occurrence of postprostatectomy incontinence (PPI).

Acknowledgements

None

References

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Figures

Pelvic floor MRI T2-weighted image of a prostate cancer patient’s mid-sagittal slice labelled with the relevant anatomy (a). Measurement of the length of the membranous urethra (MUL) in preoperative and postoperative patients are respectively illustrated in (b) and (c), the thickness measurements of the anterior and posterior margins of the membranous urethra in preoperative and postoperative patients are respectively shown in (d) and (e).

Pre- and post-operative color-coded images of the patients, clearly showing the contours of distal and proximal sphincters and intermediate longitudinal muscles fibers. The three rows of images are schematic diagrams of the urethral sphincter complex in prostate cancer patient (A1~A3), postoperative urinary continence patient (B1~B2), postoperative urinary incontinence patient (C1~C2), respectively.

Fibers tractography based on the direction of the lead eigenvector (corresponding to the primary eigenvalue) derived from DTI images. The three rows of fiber tracked images are schematic diagrams of the urethral sphincter complex in prostate cancer patient (A1~A3), postoperative urinary continence patient (B1~B3), and postoperative urinary incontinence patient (C1~C3), respectively. And the three columns of images from left to right are the proximal sphincter fiber bundle, the distal sphincter fiber bundle, and the intermediate longitudinal muscle fiber bundle in this order.

Proc. Intl. Soc. Mag. Reson. Med. 31 (2023)
2060
DOI: https://doi.org/10.58530/2023/2060