Image Characterization of Fibroids To Improve Magnetic Resonance Guided Focused Ultrasound (MRgFUS) Treatment Outcomes

Abstract

Study Objective: To investigate the effects of fibroid characteristics, as assessed by MR imaging, on Magnetic Resonance guided Focused Ultrasound (MRgFUS) treatment outcomes.Design: Retrospective analysis of 168 cases of MRgFUS ablation of uterine fibroids.Setting: Four outpatient imaging clinics where MRgFUS treatment was performed by a gynecologist.Patients: One hundred sixty eight women (ages 29-61) with symptomatic uterine fibroids.Intervention: MRgFUS ablation of fibroids using the ExAblate 2000 device according to the FDA commercial treatment guidelines.Measurements and Main Results: A total of 279 fibroids were treated with MRgFUS. Fibroids were classified by their intensity on T2 weighted images (GE SIGNA 1.5 T) relative to the normal myometrium (hyperintense, isointense, hypointense), and consistency of the fibroid (homogeneous, heterogeneous). Fibroids grouped by intensity: hyperintense (3.2%), isointense (10.4%), hypointense (61.6%), unclassified (24.7%). Fibroids grouped by consistency: homogeneous (15.4%), heterogeneous (48.0%), unclassified (36.6%). The NPV ratio was calculated as a percent of total fibroid load and as a percent of individual fibroid volume. The average total NPV was 50.8% whereas the average fibroid NPV was 55.2%. The NPV ratio for homogenous fibroids (59.2%) was greater than that for heterogeneous fibroids (51.5%) and the NPV ratio for hypointense fibroids (56.1%) was greater than that for hyperintense (29.1%) and isointense fibroids (42.2%). Trends between other treatment parameters and the percentage of hyperintense/heterogeneous fibroids at each site were identified (e.g. greater number of sonications at sites with greater percentage of hyperintense fibroids) and should be investigated further.Conclusion: Fibroid characteristics play a role in the success of MRgFUS treatment, as indicated by higher NPV ratio. Based on these results, the “ideal” fibroid would appear hypointense on T2 weighted images and homogeneous in intensity throughout the fibroid. The consideration of fibroid characteristics during patient evaluation and determination of candidacy for MRgFUS treatment could lead to improved treatment outcomes. Study Objective: To investigate the effects of fibroid characteristics, as assessed by MR imaging, on Magnetic Resonance guided Focused Ultrasound (MRgFUS) treatment outcomes. Design: Retrospective analysis of 168 cases of MRgFUS ablation of uterine fibroids. Setting: Four outpatient imaging clinics where MRgFUS treatment was performed by a gynecologist. Patients: One hundred sixty eight women (ages 29-61) with symptomatic uterine fibroids. Intervention: MRgFUS ablation of fibroids using the ExAblate 2000 device according to the FDA commercial treatment guidelines. Measurements and Main Results: A total of 279 fibroids were treated with MRgFUS. Fibroids were classified by their intensity on T2 weighted images (GE SIGNA 1.5 T) relative to the normal myometrium (hyperintense, isointense, hypointense), and consistency of the fibroid (homogeneous, heterogeneous). Fibroids grouped by intensity: hyperintense (3.2%), isointense (10.4%), hypointense (61.6%), unclassified (24.7%). Fibroids grouped by consistency: homogeneous (15.4%), heterogeneous (48.0%), unclassified (36.6%). The NPV ratio was calculated as a percent of total fibroid load and as a percent of individual fibroid volume. The average total NPV was 50.8% whereas the average fibroid NPV was 55.2%. The NPV ratio for homogenous fibroids (59.2%) was greater than that for heterogeneous fibroids (51.5%) and the NPV ratio for hypointense fibroids (56.1%) was greater than that for hyperintense (29.1%) and isointense fibroids (42.2%). Trends between other treatment parameters and the percentage of hyperintense/heterogeneous fibroids at each site were identified (e.g. greater number of sonications at sites with greater percentage of hyperintense fibroids) and should be investigated further. Conclusion: Fibroid characteristics play a role in the success of MRgFUS treatment, as indicated by higher NPV ratio. Based on these results, the “ideal” fibroid would appear hypointense on T2 weighted images and homogeneous in intensity throughout the fibroid. The consideration of fibroid characteristics during patient evaluation and determination of candidacy for MRgFUS treatment could lead to improved treatment outcomes.