MRI of the Levator Ani Muscle. Imaging Pelvic Floor Disorders. Berlin: Springer Berlin Heidelberg; 2008. pp. 89-100. [DOI: 10.1007/978-3-540-71968-7_6]

Diffusion tensor imaging and fiber tractography for the visualization of the female pelvic floor

In the past decade, the evaluation of the pelvic support for understanding pelvic floor dysfunction by means of magnetic resonance imaging (MRI) has been an emerging area of research. Both static and dynamic MRI techniques have been effectively applied as a diagnostic resource to reveal abnormalities to the muscular pelvic support, but fail to unravel the precise pathophysiology of this complex disorder. Diffusion tensor imaging (DTI) and tractography comprise enhanced MRI techniques that enable the three-dimensional visualization of anisotropic tissue, such as muscle fibers, and provide a quantitative description of tissue organization and integrity. Quantifying DTI and fiber tractography might be able to reveal microstructural abnormalities in the pelvic support that are not noticeable using conventional MRI techniques. In this article, we discuss relevant anatomy, the current state of DTI and tractography in the evaluation of the female pelvic floor, and their potential future clinical applications.

Evaluation of the female pelvic floor in pelvic organ prolapse using 3.0-Tesla diffusion tensor imaging and fibre tractography

Objectives

To prospectively explore the clinical application of diffusion tensor imaging (DTI) and fibre tractography in evaluating the pelvic floor.

Methods

Ten patients with pelvic organ prolapse, ten with pelvic floor symptoms and ten asymptomatic women were included. A two-dimensional (2D) spin-echo (SE) echo-planar imaging (EPI) sequence of the pelvic floor was acquired. Offline fibre tractography and morphological analysis of pelvic magnetic resonance imaging (MRI) were performed. Inter-rater agreement for quality assessment of fibre tracking results was evaluated using weighted kappa (κ). From agreed tracking results, eigen values (λ1, λ2, λ3), mean diffusivity (MD) and fractional anisotropy (FA) were calculated. MD and FA values were compared using ANOVA. Inter-rater reliability of DTI parameters was interpreted using the intra-class correlation coefficient (ICC).

Results

Substantial inter-rater agreement was found (κ = 0.71 [95% CI 0.63–0.78]). Four anatomical structures were reliably identified. Substantial inter-rater agreement was found for MD and FA (ICC 0.60–0.91). No significant differences between groups were observed for anal sphincter, perineal body and puboperineal muscle. A significant difference in FA was found for internal obturator muscle between the prolapse group and the asymptomatic group (0.27 ± 0.05 vs 0.22 ± 0.03; P = 0.015).

Conclusion

DTI with fibre tractography permits identification of part of the clinically relevant pelvic structures. Overall, no significant differences in DTI parameters were found between groups.

Key Points

• Diffusion tensor MRI offers new insights into female pelvic floor problems.

• DTI allows 3D visualisation and quantification of female pelvic floor anatomy.

• DTI parameters from pelvic floor structures can be reliably determined.

• No significant differences in DTI parameters between groups with/without prolapse.