Multi-modal Medical Imaging Methods In Assessment And Prediction Of Uterine Artery Embolization For Fibroids

Part I: Entropy of T2-weighted Imaging Combined with Apparent Diffusion Coefficient in Prediction of Uterine Leiomyoma Volume Response after Uterine Artery EmbolizationObjective To determine the potential value of entropy of T2-weighted imaging combined with apparent diffusion coefficient(ADC) before uterine artery embolization(UAE) for prediction of uterine leiomyoma volume reduction(VR) after UAE.Materials and Methods In this prospective study, 11 patients with uterine leiomyomas who underwent pelvic magnetic resonance imaging including diffusion-weighted imaging before and 6 months after UAE were included. A total number of 16 leiomyomas larger than 2 cm in diameter were evaluated. The volume of each leiomyoma before and after UAE was determined, and the percentage change in volume was calculated. Entropy of T2-weighted imaging and ADC before UAE were assessed. Pearson correction coefficients were calculated between leiomyoma VR after UAE and age, leiomyoma volume, ADC, and entropy, respectively. Multiple regression analysis was performed to investigate the parameters that determine the VR after UAE. Receiver operating characteristic curve analysis was used todetermine the sensitivity and specificity of ADC, entropy and the combination of ADC, and entropy for predicting volume response.Results The mean leiomyoma VR was 58.9%(range 25.8%–95.0%) in the 6-month follow-up. The mean ADC of leiomyomas was 1.37×10-3 mm2/s(range 1.05×10-3 mm2/s–2.32×10-3 mm2/s) and the mean entropy of T2-weighted imaging was 5.36(range 4.62–5.91) before UAE. ADC and entropy were significantly correlated with leiomyoma VR, respectively(r = 0.61, P=0.012; r = 0.73, P = 0.001). On multiple regression analysis, a combination of ADC and entropy constituted the best model for determining leiomyoma VR using Akaike information criterion. For predicting ≥50% VR, the optimal cutoff value of ADC was 1.39×10-3 mm2/s(sensitivity 45.5%, specificity 80.0%) and the optimal cutoff value of entropy was 5.15(sensitivity 90.9%, specificity 60.0%). The combination of ADC and entropy(area under the curve [AUC] 0.86) provided better classification accuracy than ADC or entropy alone(AUC 0.69 and 0.82, respectively).Conclusions Pre-UAE entropy of T2-weighted imaging and ADC of leiomyomas were significantly correlated with the leiomyoma VR 6 months after embolization. Higher entropy and higher ADC may be related to greater leiomyoma VR after UAE. A combination of entropy and ADC may have predictive value for leiomyoma VR after UAE.Part II: Assessment of diffusion characteristics of uterine fibroids pre- and post-uterine fibroid embolization using diffusion-weighted imaging and intravoxel incoherent motion imagingObjective Diffusion-weighted imaging(DWI) is a functional imaging method that depicts water molecule microscopic movement in vivo. Recently, a new contrast-free technique based on DWI named intravoxel incoherent motion imaging(IVIM) has attracted more and more interest, as it can account for molecular diffusion driven by thermal energy as well as perfusion-based pseudo-diffusion. The aim of the study was to determine the change of diffusion(ADC) and contrast-free perfusion-related parameter(f value from IVIM) of uterine fibroids following UAE.Materials and Methods In total, 15 symptomatic female patients(age range 29–58 years; mean 43 years) with uterine fibroids who underwent pelvic MRI and DWI within 10 days before and six months after UAE were included. Imaging sequences included conventional T1- and T2-weighted imaging, dynamic contrast-enhanced imaging and DWI. DWI was acquired using a single-shot spin-echo echo-planar sequence(b-value = 0, 1000 s/mm2). In 4 of the total patients, multi-b-value DWI was also obtained to calculate the IVIM parameters(b-value = 0, 50, 100, 200, 500, 800, 1000, 1200 s/mm2). Pre- and post-UAE ADCs were calculated for all patients, and f values were fitted using a non-linear regression algorithm for the 4 patients. A nonparametric pairwise Wilcoxon rank–sum test was used to detect whether there were significant changes for ADC and f value after UAE.Results After a follow-up of 6 months, all patients felt a relief of symptoms including menorrhagia and bulk-related symptoms. A total number of 20 fibroids in the 15 patients were evaluated for ADC. The mean ADC values were 1.22×10-3 mm2/s(range, 0.86–1.65×10-3 mm2/s) before UAE and 1.55×10-3 mm2/s(range, 0.92–1.85×10-3 mm2/s) after UAE. A significant increase in ADC pre- and post-UAE was observed(P = 0.001). A total number of 5 fibroids in the 4 patients were evaluated for IVIM. The f values were significantly lower(mean, 10.48%; range, 7.96%–14.21%) after UAE than before UAE(mean, 26.69%; range, 19.00%–33.19%; P = 0.043).Conclusions The ADC of fibroids rises post-UAE, likely reflecting degeneration and cellular necrosis. The f value decreases post-UAE, probably due to the devascularization induced by UAE procedure.Part III: Application of color-coded quantitative digital subtraction angiography in the procedure of uterine artery embolization: Initial experienceObjective This study aimed to monitor peri-embolization relevant blood flow information in the uterine artery embolization operation by using color-coded quantitative digital subtraction angiograph(CCQ-DSA) and to explore its potential ability in the assessment of the embolization endpoint.Materials and Methods Internal review board approval and informed consent were obtained for this study. Twenty women(mean age, 36.3 years) underwent bilateral UAE of symptomatic leiomyomas were recruited. The CCQ-DSA imaging before and after the embolization were obtained by using the post-processing software(i Flow). The CCQ-DSA imaging determined the quantitative parameters of each pixel piont calculated from time-intensity curve including time to peak(TTP), signal intensity peak(SIP),maximum slope(MS),area under the curve(AUC). The relative values(r TTP, r SIP, r MS, r AUC) were defined as the TTP, SIP, MS, AUC values of ROIs at embolization site minus IP, MS, AUC values of homolateral middle segment uterine artery. Paired t-test was performed to determine the difference of the r TTP, r SIP, r MS, r AUC values at the embolization site between the per-and post-UAE procedure. T2-weighted images were obtained before and after 6 mouths of the emboliztion procedure.Results All the 18 patients completed the embolization successfully and finally 14 CCQ-DSA imaging were obtained. The r TTP value of the embolization site of the feeding artery was significantly prolonged after the treatment(P < 0.01). Statistical decrease were observed between pre- and postprocedural r IP, r MS, r AUC values(P < 0.01), respectively. The mean percentage of leiomyoma volume reduction was 58.9%(range 25.8%–95.0%) in the 6-month follow-up.Conclusions CCQ-DSA may monitor peri-embolization relevant blood flow information and provide a feasible quantitative measurement in the assessment of uterine artery embolization endpoints.