Three-Dimensional Quantitative Assessment of Lesion Response to MR-guided High-Intensity Focused Ultrasound Treatment of Uterine Fibroids

Rationale and Objectives: To investigate the response after magnetic resonance-guided high-intensity focused ultrasound (MRgHIFU) treatment of uterine fibroids (UF) using a three-dimensional (3D) quantification of total and enhancing lesion volume (TLV and ELV, respectively) on contrast-enhanced MRI (ceMRI) scans. Methods and Materials: In a total of 24 patients, ceMRI scans were obtained at baseline and 24hours, and 6, 12, and 24months after MRgHIFU treatment. The dominant lesion was assessed using a semiautomatic quantitative 3D segmentation technique. Agreement between software-assisted and manual measurements was then analyzed using a linear regression model. Patients were classified as responders (R) or nonresponders (NR) on the basis of their symptom report after 6months. Statistical analysis included the paired t-test and Mann-Whitney test. Results: Preprocedurally, the median TLV and ELV were 263.74cm³ (30.45-689.56cm³) and 210.13cm³ (14.43-689.53cm³), respectively. The 6-month follow-up demonstrated a reduction of TLV in 21 patients (87.5%) with a median TLV of 171.7cm³ (8.5-791.2cm³; P<.0001). TLV remained stable with significant differences compared to baseline (P<.001 and P=.047 after 12 and 24months). A reduction of ELV was apparent in 16 patients (66.6%) with a median ELV of 158.91cm³ (8.55-779.61cm³) after 6months (P=.065). Three-dimensional quantification and manual measurements showed strong intermethod agreement for fibroid volumes (R²=.889 and .917) but greater discrepancy for enhancement calculations (R²=.659 and .419) at baseline and 6months. No significant differences in TLV or ELV were observed between clinical R (n=15) and NR (n=3). Conclusions: The 3D assessment has proven feasible and accurate in the quantification of fibroid response to MRgHIFU. Contrary to ELV, changes in TLV may be representative of the clinical outcome.