Application Of Static And Dynamic Pelvic Floor MRI And DTI In Female Patients With Stress Urinary Incontinence

Background and PurposeStress urinary incontinence(SUI)refers to the involuntary urine flow from the external urethra when the abdominal pressure increases(such as sneezing,coughing,laughing,etc.)without the detrusor muscle contracting.SUI is a common pelvic floor dysfunction disease in women,and its prevalence increases with age.With the intensification of global aging,the prevalence of SUI rises sharply,which will seriously affect the daily work and life of patients.Due to the complexity of female pelvic floor structure and urinary continence mechanism,the etiology and mechanism of SUI are not yet fully understood.The purpose of this study was to quantitatively evaluate the morphology and function of pelvic floor structures in women with stress urinary incontinence(SUI)using dynamic and static pelvic floor MRI and pelvic floor DTI techniques,and to explore the predictive value of pelvic floor MRI-related parameters for SUI.Materials and MethodsFrom July 2020 to February 2022,we prospectively collected 45 patients were diagnosed with SUI by urodynamic examination and 49 age-matched healthy volunteers were confirmed to be free of SUI symptoms by the International Consultation Committee on Incontinence Questionnaire(ICI-Q-LF)survey in the First Affiliated Hospital of Zhengzhou University.Basic clinical information such as menopausal status,number of deliveries,mode of delivery,and body mass index(BMI)were collected from all subjects.All subjects underwent dynamic and static pelvic floor MRI scanning and pelvic DTI scanning using a cross-sectional single excitation spin-gradient echo(SE-GRE)pulse sequence.(1)Measurement of urethra incline angle(UIA),distance from bladder neck(BN)to pubococcygeal line(PCL)(BN-PCL),bilateral puborectalis muscle(PRM)thickness,iliocococcygeal muscle(ICM)thickness,maximum transverse diameter of the levator hiatus width(LHW),levator plate angle(LPA),iliocococcygeal angle(ICA),thickness of the internal and external sphincter of the middle urethra and functional urethral length(FUL)on static pelvic floor MRI.(2)The UIA,BN-PCL,LPA,and FUL were measured on the dynamic pelvic floor MRI maximal strain phase and the difference of UIA、BN-PCL、LPA、FUL between static and dynamic MRI was calculated,at the same time,the bladder neck funneling and urethra opening were observed on static and dynamic images of static and dynamic MRI.(3)The original DTI images were post-processed to obtain images of the muscle fiber bundles of the urethral sphincter complex,puborectalis,iliococcygeus,and obdurator internus(OI)muscles;the images were observed and the anisotropy fraction(FA),apparent diffusion coefficient(ADC)values and three eigenvalues(λ1,λ2,λ3)of the muscle fibers of the middle urethral circular sphincter,central longitudinal muscle and puborectalis,iliococcygeus,and obdurator internus(OI)muscles were measured.Ten subjects in controls were selected for three pelvic floor DTI scans within three days to evaluate the reproducibility of DTI-derived parameters.The above measurements of the relevant parameters for the measurement data were analyzed by the Kolmogorov-Smirnov test for conformity to the normal distribution,and x±s or M(P25 P75)(median M,25th percentile,75th percentile)were used for statistical description;two independent samples t-test or non-parametric Wilcoxon rank sum test were used for comparison of parameters between two groups,and χ2 test was used for comparison between groups for qualitative data.Repeatability test was carried out on 10 healthy subjects by intraclass correlation coefficient(ICC).Binary logistic regression was used to analyze the pelvic floor MRI parameters with statistically significant differences and to screen out the parameters associated with the occurrence of SUI;ROC curves were established and the AUC values,sensitivities,specificities and optimal thresholds of the relevant parameters were calculated.Results1.The results of the comparison of dynamic and static pelvic floor MRI parameters between the SUI group and the control group:(1)Among the cystourethra-related parameters:the thickness of the middle urethral external sphincter,static and dynamic maximal strain phase FUL,BN-PCL values were significantly reduced in the SUI group compared with the control group{(2.08 ±0.37)mm vs.(2.46±0.36)mm,(26.75±2.13)mm vs.(29.65±2.42)mm,(18.19±3.42)mm vs.(23.97±4.09)mm,(17.15±4.91)mm vs.(20.31±4.23)mm,[-2.18(-9.24,6.21)]mm vs.[13.21(4.78,15.55)]mm,respectively}(all P<0.01);the static and dynamic maximal strain phase UIA,the difference of UIA,FUL and BN-PCL between static status and maximal strain phase was significantly increased{[6.47(-5.67,9.78)]° vs.[-5.37(-10.26,4.54)]°,(51.98 ± 19.79)° vs.(28.13 ±15.76)°,[48.21(36.97,65.94)]° vs.[30.11(22.99,35.35)]°,(8.18±3.94)mm vs.(5.67 ± 3.47)mm,[17.49(13.39,23.04)]mm vs.[7.87(6.26,13.31)]mm,respectively}(all P<0.05);the positive rate of the bladder neck funneling sign in the static and dynamic maximal strain phase and the positive rate of the urethral opening sign in the dynamic maximal strain phase in the SUI group were significantly greater than those in the control group[(80%vs.42.86%),(100%vs.51.02%),(51.11%vs.2.04%),respectively](all P<0.001).(2)Among the parameters related to the levator ani muscle:the values of left PRM thickness and right PRM thickness were significantly reduced in the SUI group compared with the control group[(6.01±1.78)mm vs.(7.21 ± 2.18)mm,(5.43 ± 1.66)mm vs.(6.67±1.88)mm,respectively](all P<0.001);the values of LHW,static and dynamic maximal strain phase LPA and LPA difference were significantly increased in the SUI group compared with the control group{(35.03±3.53)mm vs.(32.20±3.39)mm,(35.03±5.90)° vs.(31.16±4.19)°,(49.40±8.30)° vs.(41.58±5.37)°,[12.93(8.96,21.40)]° vs.10.01(7.99,12.09)]°,respectively}(all P<0.05).2.Comparison of pelvic floor DTI parameters between the SUI group and the control group:the FA values of the middle urethral circular sphincter and the puborectalis muscle in the SUI group were significantly decreased {(0.24±0.03)vs.(0.2 7±0.02),[0.28(0.26-0.32)]vs.[0.30(0.28-0.33)],respectively}(all P<0.05);the ADC values,λ2 and λ3 value of the middle urethral circular sphincter and the puborectalis muscle increased significantly {(1.61±0.16)10-3 mm2/s vs.(1.50 ±0.17)10-3 mm2/s,(1.53±0.17)10-3 mm2/s vs.(1.45 ± 0.13)10-3 mm2/s,(1.60 ±0.30)10-3 mm2/s vs.(1.45±0.16)10-3 mm2/s,(1.47 ± 0.21)10-3 mm2/s vs.(1.39 ±0.17)10-3 mm2/s,(1.24±0.22)10-3 mm2/s vs.(1.11±0.16)10-3 mm2/s,(1.09 ±0.19)10-3 mm2/s vs.(1.00 ± 0.18)10-3 mm2/s,respectively}(all P<0.01);DTI parameters of central longitudinal muscle,iliococcygeus muscle and obturator internus muscle in the middle urethra did not change significantly(P>0.05).3.The ICC of the obturator internus DTI-derived parameters in 10 healthy subjects was 0.63-0.79,suggesting good reproducibility.4.Binary logistic regression analysis showed that the dynamic maximal strain phase BN-PCL,UIA,FUL and urethral open sign were significantly correlated with the occurrence of SUI,with ORs of 0.607,0.819,1.536,and 12.499,respectively.The ROC curve analysis showed that the AUC values of BN-PCL,UIA,FUL,and urethral opening sign were 0.842,0.845,0.857,and 0.746,respectively;and the sensitivities were 81.4%,74.4%,79.1%,and 51.2%,respectively;the specificities were 71.4%,79.6%,79.6%,and 98%,respectively;the optimal thresholds were 6.93mm,37.35° and 21.67mm,respectively.The ROC curve analysis of the above four pelvic floor parameters in two,three and four parameter combinations showed that the AUC values were 0.935,0.917,0.917,0.927,0.920,0.908,0.961,0.969,0.957,0.950,0.976,respectively,suggesting that the combined diagnostic efficacy of any parameter was greater than that of any single parameter,in which BN-PCL+UIA+FUL with the largest sensitivity(97.7%)could be used as the optimal index for predicting SUI,providing an important imaging basis for clinicians to diagnose and treat SUI at an early stage.Conclusions1.Dynamic and static pelvic floor MRI and pelvic floor DTI technology can intuitively and accurately comprehensively assess the changes in the morphology and function of the levator ani muscle and urethra in patients with SUI;thinning of the puborectalis muscle and urethral sphincter,Increased bladder neck urethral mobility,shortened FUL,and the muscle fibers fracture are the main manifestations of structural changes of the levator ani muscle and urethra in patients with SUI.2.Among the pelvic floor MRI parameters,the dynamic maximal strain phase BN-PCL,UIA,FUL and urethral open sign have certain value in predicting SUI,and the combined application of various parameters can significantly improve the prediction efficiency of SUI.