Case notes
Uterine fibroid embolization (UFE) and magnetic resonance (MR)–guided high-intensity focused ultrasound (HIFU) ablation are increasingly used in clinical practice as nonsurgical treatment modalities for symptomatic uterine fibroids. However, UFE is inevitably accompanied by exposure to ionizing radiation, and it is usually followed by severe pelvic pain. MR-HIFU ablation requires a lengthy procedure time, especially when treating larger fibroids; to overcome this drawback, a new strategy, volumetric MR-HIFU ablation, has been recently developed. While the conventional point-by-point sonication method only achieves a relatively small ablation zone, volumetric ablation can target treatment cells ranging from 4-16 mm in axial diameter, and this is expected to reduce treatment time.
We successfully treated 2 women who had very large symptomatic uterine fibroids with volumetric MR-HIFU ablation therapy. In both cases, the procedural time was much shorter than is usually needed for the conventional technique.
The first patient, a 40-year-old woman with a single large uterine fibroid, reported urinary frequency and a palpable mass. T2-weighted MR imaging (MRI) showed a 12.3-cm subserosal uterine fibroid (volume, 599.5 mL) with relatively low signal intensity ( Figures 1 and 2 ) .
Treatment was performed on an outpatient basis using an extracorporeal MR-HIFU system (Sonalleve; Royal Philips Electronics, Amsterdam, The Netherlands; not yet sold in the United States) capable of performing volumetric ablation. We targeted 49 treatment cells (8 mm, n = 1; 12 mm, n = 26; 16 mm, n = 22) with a power of 128.8 ± 13 W ( Figure 3 ) . Treatment took 163 minutes from the first to last sonication, and MR room time was 205 minutes. Immediate follow-up contrast-enhanced MRI showed 431.4 mL of nonperfused volume (NPV), representing 72% of the fibroid volume ( Figures 4 and 5 ) . Treatment speed (NPV divided by treatment time) was 158.8 mL/h.
The patient had no skin burns or other complications. After treatment, she reported self-limited lower abdominal discomfort for 1 day. Four months later, the patient, who was 4 weeks pregnant, underwent transabdominal ultrasonography, which estimated the fibroid volume at 42.8% (256.4 mL; 9 × 8 × 6.8 cm 3 ) of the baseline ( Figure 6 ) . She reported that urinary frequency had completely resolved, and the mass was barely palpable.
The second patient was a 43-year-old woman with a large fibroid causing urinary frequency; a melonlike mass was palpable. MRI showed a 13-cm subserosal fibroid (643.5 mL) with intermediate to low signal intensity on a T2-weighted image ( Figure 7 ) .
