Diffusion-weighted imaging in uterine artery embolisation: do findings correlate with contrast enhancement and volume reduction?

The utility of apparent diffusion coefficients for predicting treatment response to uterine arterial embolization for uterine leiomyomas: a systematic review and meta-analysis

PURPOSE

Apparent diffusion coefficient (ADC) values, which are derived from diffusion-weighted imaging, have a potential role for predicting treatment response. A systematic review was conducted to examine the value of baseline ADC values for predicting leiomyoma size reduction after uterine arterial embolization (UAE).

METHODS

Study selection, quality appraisal and data extraction were conducted independently by two authors. Statistical analyses included the calculation of weighted means and summary correlation coefficients (under the random effects model).

RESULTS

Eleven studies consisting of a total of 258 patients (age, weighted mean±standard deviation [SD], 43.1±10.1 years) were included. The weighted mean±SD ADC value was 1.2±1.5 ×10-3 s/mm2 at baseline (ten studies) and 1.3±2.8 ×10-3 s/mm2 at approximately 6 months after embolization (six studies). The weighted mean percentage leiomyoma volume reduction (VR) at 6 months was 47.1%±35.6% (seven studies). Based on four studies, the weighted summary correlation coefficient for the correlation between baseline ADC and leiomyoma VR at approximately 6 months was not significant (r=0.40; 95% CI, -0.07 to 0.72; I2=69.7%). No associations were found in three of the four studies that examined changes in ADC values as a predictor.

CONCLUSION

Due to high heterogeneity, it is unclear whether ADC may be useful for predicting treatment responses to UAE.

Multiparametric MRI Characterization of Funaki Types of Uterine Fibroids Considered for MR-Guided High-Intensity Focused Ultrasound (MR-HIFU) Therapy

RATIONALE AND OBJECTIVES

To compare quantitative multiparametric magnetic resonance imaging (mpMRI) data of symptomatic uterine fibroids being considered for MR-guided high-intensity focused ultrasound ablation with fibroid characterization based on the Funaki Classification scheme.

MATERIALS AND METHODS

This was a prospective, Institutional Review Board -approved, Health Insurance Portability, and Accountability Act-compliant study. Informed consent was obtained. From December 2013 to April 2015, 48 women with symptomatic fibroids underwent screening with mpMRI protocol including sagittal/axial T2-weighted fast spin-echo, sagittal diffusion-weighted, and sagittal dynamic contrast-enhanced 3D T1-weighted gradient echo imaging on a 3T magnet. All fibroids were assigned Funaki type 1, 2, or 3 based on T2-weighted imaging. Differences in size, perfusion, and diffusion/intravoxel incoherent motion parameters among the three Funaki types were determined using linear mixed model. A logistic regression analysis was performed to select the best model in predicting type 3 fibroids.

RESULTS

A total of 100 fibroids were assessed (20 type 1, 66 type 2, and 14 type 3). Apparent diffusion coefficient and D of type 3 fibroids were significantly higher than those of type 1 (P < 0.0001, P < 0.0001) and 2 fibroids (P = 0.004, P < 0.0001) respectively. Transfer constant of type 3 fibroids was significantly higher than type 1 (P = 0.0357), but not than type 2 (P = 0.0752). A cutoff value of D = 1 × 10^-3 mm²/s offers an accuracy, sensitivity, and specificity of 76%, 71%, and 77%, respectively, for the diagnosis of Funaki 3 fibroids.

CONCLUSION

mpMRI-derived quantitative parameters may enable a more objective selection of patients prior to MR-guided high-intensity focused ultrasound therapy.

European Society of Urogenital Radiology (ESUR) Guidelines: MR Imaging of Leiomyomas

OBJECTIVE

The aim of the Female Pelvic Imaging Working Group of the European Society of Urogenital Radiology (ESUR) was to develop imaging guidelines for MR work-up in patients with known or suspected uterine leiomyomas.

METHODS

Guidelines for imaging uterine leiomyomas were defined based on a survey distributed to all members of the working group, an expert consensus meeting at European Congress of Radiology (ECR) 2017 and a critical review of the literature.

RESULTS

The 25 returned questionnaires as well as the expert consensus meeting have shown reasonable homogeneity of practice among institutions. Expert consensus and literature review lead to an optimized MRI protocol to image uterine leiomyomas. Recommendations include indications for imaging, patient preparation, MR protocols and reporting criteria. The incremental value of functional imaging (DWI, DCE) is highlighted and the role of MR angiography discussed.

CONCLUSIONS

MRI offers an outstanding and reproducible map of the size, site and distribution of leiomyomas. A standardised imaging protocol and method of reporting ensures that the salient features are recognised. These imaging guidelines are based on the current practice among expert radiologists in the field of female pelvic imaging and also incorporate essentials of the current published MR literature of uterine leiomyomas.

KEY POINTS

• MRI allows comprehensive mapping of size and distribution of leiomyomas. • Basic MRI comprise T2W and T1W sequences centered to the uterus. • Standardized reporting ensures pivotal information on leiomyomas, the uterus and differential diagnosis. • MRI aids in differentiation of leiomyomas from other benign and malignant entities, including leiomyosarcoma.

Monitoring Leiomyoma Response to Uterine Artery Embolization Using Diffusion and Perfusion Indices from Diffusion-Weighted Imaging

Purpose

To investigate the potential of diffusion and perfusion indices (ADC and perfusion fraction f) from DWI at 3.0 T in monitoring treatment response to uterine artery embolization (UAE) at 6-month follow-up.

Methods

Twelve female patients with uterine fibroids who underwent 3.0-T pelvic DWI before and 6 months after UAE were included. ADC and perfusion fraction f were calculated from DWI. The Wilcoxon signed-rank test and Spearman rank correlation test were used for statistics.

Results

Seventeen fibroids were studied. The median ADCs showed a significant increase from 1.20 × 10⁻³ mm²/s (range, 0.86–1.66 × 10⁻³ mm²/s) at baseline to 1.56 × 10⁻³ mm²/s (range, 1.00–1.86 × 10⁻³ mm²/s) at 6-month follow-up (P = 0.0003). Conversely, the median perfusion fraction f was significantly decreased after UAE (P = 0.0001), with a median pre-UAE value of 14.2% (range, 6.7%–17.6%) and a median post-UAE value of 9.2% (range, 3.2%–14.6%). Significant correlations were found between fibroid volume reduction rate and percentage changes in ADC and perfusion fraction f at 6-month follow-up relative to baseline, with ρ values of −0.50 (P = 0.04) and 0.55 (P = 0.02), respectively.

Conclusion

ADC and perfusion fraction f obtained from DWI at 3.0 T may help to evaluate treatment response to UAE.

Non-oncologic applications of diffusion-weighted imaging (DWI) in the genitourinary system

Diffusion-weighted imaging (DWI) has become an increasingly used tool in abdominal and pelvic magnetic resonance imaging (MRI), primarily in the oncologic setting. DWI sequences are being added to routine MRI protocols at many institutions, and as its use has spread, more non-oncologic applications have been explored. The purpose of this article is to provide a review of DWI applications in inflammatory, infectious, autoimmune-mediated, and ischemic processes affecting the genitourinary system.