G.A. Holland, MD¹, Y. Inbar, MD², J. Rabinovici, MD²; ¹Burlington/US, ²Tel Aviv/IL

Purpose
MR guided Focused Ultrasound Surgery (MRgFUS) uses MR to target, and control ultrasound thermal ablation of fibroids. Injected microbubbles increase the absorption of acoustic energy thus augmenting ablations performed with FUS. The purpose of this study was to evaluate an enhanced sonographic MRgFUS (es MRgFUS) treatment of fibroids that sonographically creates microbubbles in targeted tissues without intravenous contrast.

Material and methods
18 pre or perimenopausal adult women (35-52 years old) with symptomatic fibroids were treated with es MRgFUS. Gynecological examination and MRI confirmed a diagnosis of symptomatic fibroids. Treatments were with conscious sedation on an ExAblate 2000 (InSightec, Israel) integrated into a 1.5 Tesla MR scanner (General Electric). Each patient was treated with esMRgFUS and regular MRgFUS. The dose volume was calculated for both forms of sonication and then ratios between es MRgFUS and regular MRgFUS were calculated. Contrast enhanced scans were also performed.

Results
The area of nonperfusion was limited to the fibroid capsule. No severe adverse events were attributable to the es MRgFUS sonications. The effective dose volumes of eMRgFUS were 1.5 times greater than regular MRgFUS at less than 7 cm of depth. The dose volume ratio was even more marked with two hypervascular fibroids with ratios of 3.1 and 4.7.

Conclusion
This initial study demonstrated that esMRgFUS is safe, and produces larger effective dose volumes than regular MRgFUS, This difference is even greater in previously very difficult to treat hypervascular fibroids with es MRgFUS having up to 4.7 times greater effective dose volume. This results in either a shorter duration of a fibroid treatment, permits the treatment of hypervascular fibroids, or greater volume of fibroid.