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Axial diffusivity and kurtosis derived based on DWI reflect microstructure changes in patients with in stress urinary incontinence patients
Kun Ou1, Weiyn Vivian Liu2, and Kun Zhang1,3
1Department of Radiology, First Affiliated Hospital of Hunan University of Chinese Medicine, Changsha, China, 2MR Research, GE Healthcare, Beijing, China, 3College of Integrated Traditional Chinese and Western Medicine, Hunan University of Chinese Medicine, ChangSha, China

Synopsis

Keywords: Muscle, Diffusion/other diffusion imaging techniques, Diffusion kurtosis imaging

Stress urinary incontinence (SUI) is the most common form of urinary incontinence. However, in patients with SUI, the pelvic floor muscles generally have no obvious radiographic abnormalities. This study applied diffusion-weighted imaging with different analysis models and found that patients with SUI had significantly lower FA and Da values based on gaussian-distributed water movement and higher values in the Ka based on non-gaussian-distributed water movement compared to the healthy volunteers. This study showed both DTI and DKI derived parameters can detect microstructure changes in the the pubic visceral muscle of the SUI patients.

Introduction

The prevalence of urinary incontinence is as high as 28% and stress urinary incontinence (SUI) is the most common form1,2. SUI is caused by involuntary loss of urine during coughing or laughing in which bladder pressure exceeds the capacity of holding closed3. The periurethral, paraurethral, and pubic-urethral connective tissue may be damaged during pregnancy and labor. In addition, the pubic visceral muscle forms the medial portion of the levator ani muscle and is susceptible to injury during childbirth4,5. Magnetic Resonance Imaging (MRI) is commonly used to visualize pelvic floor anatomy and pelvic floor muscle defects. However, in patients with SUI, the pelvic floor muscles generally have no obvious structural abnormalities6. Therefore, more imaging studies attempted to detect microstructural changes in the pelvic floor muscles via diffusion weighted imaging. Previous studies in assessment of skeletal muscle injury using diffusion tensor imaging(DTI) have confirmed significant different DTI-derived parameters such as decreased FA and increased MD for injured pelvic floor muscles7,8.Diffusion kurtosis imaging(DKI) is an extension of diffusion weighted imaging and more sensitive to changes in tissue microarchitecture 9. Therefore, this study aimed to explore the feasibility of DKI in evaluation of the muscle function between women with and without SUI.

Material and methods

51 healthy volunteers and 54 patients with SUI underwent pelvic floor examination using routine MRI and axial DTI imaging on a 3.0-T MR scanner (Signa HDxt, GE Healthcare). DKI postprocessing was performed and analyzed on Advanced Workstation 4.6 (GE Healthcare). Three diffusional kurtosis (DK) maps including mean kurtosis (MK), axial kurtosis (Ka), and radial kurtosis (Kr) and four diffusion tensor (DT) maps containing fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (Da), and radial diffusivity (Dr) were obtained. The regions of interest (ROIs) was circled in bilateral pubic visceral muscles for three times and average.

Results

There was no significant difference of all parameter in DKI sequence between the left and right sides. Patients with SUI had significantly lower values in the FA, Da (P < 0.05, P < 0.05) as well as higher values in the Ka (P <0.05) compared with the healthy volunteers. (Table 1). In the healthy volunteers, the Da was significantly higher than Dr (P < 0.05). The Kr was significantly higher than Ka (P < 0.05).

Discussion

We demonstrated diffusion-based models can reflect the function of bilateral pubic visceral muscles. Our study shows that patients with SUI had significantly lower values in the FA and Da, which is similar to previous studies.7,8 In the healthy volunteers, the Da was significantly higher than Dr. Da represents the diffusivity in the direction parallel to the length of the pubovisceral muscle fibers, and Dr represents the average diffusivity in all directions perpendicular to the length of the pubic visceral muscle fibers. Our result was consistent with the finding of the least restricted for water molecules along the longitudinal diffusion displacement of muscle fibers10. When muscle injuries, muscle fibrosis and fat accumulation disorganizes fiber bundles, leading to Da dropping. We also found patients with SUI had significantly higher values in the Ka than the healthy volunteers. In the healthy volunteers, the Kr was significantly higher than Ka. When K is greater than 0, a larger value indicates a larger deviation from the Gaussian distribution, and the K value is also positively correlated with the complexity of the internal microstructure 4,11. Ka refers to the kurtosis parallel to the length of the pelvic floor muscle fibers, and Kr refers to the average kurtosis of all directions perpendicular to the length of the pelvic floor muscle fibers. It is generally believed that the Kr value is larger than the Ka value, which may be related to the barrier of the endomysium, perimysium, cytoskeleton and capillary network, forming a more complex and heterogeneous microstructure in the vertical direction4. Similar to Da value, elevated Ka values in SUI patients may be due to edema, fat deposition, and fibrosis after muscle injury. Our results showed Ka and Da complement each other and both can reflect muscle injury.

Conclusion

DKI sequence can detect changes in the microstructure of the pubic visceral muscle including lower Da and FA values and higher Ka values for SUI patients. It had potential in discovering functional alteration in injured muscle induced SUI.

Acknowledgements

No acknowledgement found.

References

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  11. Lazar M, Jensen JH, Xuan L, et al. Estimation of the orientation distribution function from diffusional kurtosis imaging. Magn Reson Med. 2008; 60(4):774-781. doi:10.1002/mrm.21725

Figures

Figure 1 Representative regions of interest (ROIs) in both pubovisceral muscles. (A) Axial kurtosis map; (B) Fractional anisotropy map; (C) Axial diffusivity map

Table 1 DTI and DKI parameters between healthy volunteers and patients with SUI.

Proc. Intl. Soc. Mag. Reson. Med. 31 (2023)
4053
DOI: https://doi.org/10.58530/2023/4053