Uterine leiomyomas: MR imaging-guided focused ultrasound surgery--imaging predictors of success

Abstract

Purpose: To retrospectively assess the magnetic resonance (MR) imaging predictors of success at reducing uterine leiomyoma volume and achieving patient symptom relief 12 months after MR imaging-guided focused ultrasound surgery.

Materials and methods: This single-center retrospective analysis of 71 symptomatic fibroids in 66 women was approved by the institutional review board and was HIPAA-compliant. Patients were treated with MR imaging-guided focused ultrasound surgery. The volume of treated fibroid and nonperfused volume (NPV) were calculated with software, while symptom outcome was assessed with a symptom severity score (SSS). Fibroids were classified as hyperintense or hypointense relative to skeletal muscle on pretreatment T2-weighted MR images.

Results: Baseline volume of treated fibroids was 255.5 cm(3) +/- 201.7 (standard deviation), and baseline SSS was 61.5 +/- 14.9. Both pretreatment fibroid signal intensity (SI) and posttreatment NPV predicted 12-month volume reduction independently: Fibroids with an NPV of at least 20% or with low SI both showed significantly larger volume reduction (17.0% +/- 13.0 and 17.2% +/- 20.1, respectively) than fibroids with an NPV less than 20% or with high SI (10.7% +/- 18.2 and no significant change, respectively). Patients whose fibroids demonstrated an NPV of at least 20% also experienced a larger decrease in SSS than did patients with fibroids with an NPV less than 20% (50.1% +/- 19.8 vs 32.6% +/- 29.9).

Conclusion: Fibroids with low SI on pretreatment T2-weighted MR images were more likely to shrink than were ones with high SI. The larger the NPV immediately after treatment, the greater the volume reduction and symptom relief were. These findings may help both in selecting appropriate patients for MR-guided focused ultrasound surgery and in predicting patient outcome.

Figure 1a:

(a) T2-weighted axial MR image of a hypointense fibroid in a 42-year-old patient before MR-guided focused ultrasound surgery. (b) T1-weighted gadolinium-enhanced axial MR image of the same fibroid immediately after treatment. The outlines of treated fibroid and NPV were contoured with electronic calipers to compute the area per section by using volumetric analysis software.

Figure 1b:

(a) T2-weighted axial MR image of a hypointense fibroid in a 42-year-old patient before MR-guided focused ultrasound surgery. (b) T1-weighted gadolinium-enhanced axial MR image of the same fibroid immediately after treatment. The outlines of treated fibroid and NPV were contoured with electronic calipers to compute the area per section by using volumetric analysis software.

Figure 2a:

(a) T2-weighted axial MR image of a hypointense fibroid in a 46-year-old patient before MR-guided focused ultrasound surgery. (b) T1-weighted gadolinium-enhanced axial MR image of the same fibroid immediately after treatment. The outlines of treated fibroid and NPV were contoured with electronic calipers to compute the area per section by using volumetric analysis software.

Figure 2b:

(a) T2-weighted axial MR image of a hypointense fibroid in a 46-year-old patient before MR-guided focused ultrasound surgery. (b) T1-weighted gadolinium-enhanced axial MR image of the same fibroid immediately after treatment. The outlines of treated fibroid and NPV were contoured with electronic calipers to compute the area per section by using volumetric analysis software.

Figure 3:

Bar graph shows volume reduction at 6- and 12-month follow-up in hypointense (teal columns, n = 33) and hyperintense (red columns, n = 38) fibroids. Volume reduction is expressed as a percentage of the initial volume of the treated fibroid. Above each column the fibroid volume change is shown, with the range in parentheses. a = P < .05 versus zero, b = P < .05 versus hypointense fibroids at the same time, MRgFUS = MR-guided focused ultrasound surgery.

Figure 4:

Graph shows relationship between NPV immediately after MR-guided focused ultrasound surgery and volume changes of treated fibroid at 12-month follow-up. Fibroid volume change = −2.7 − 0.50 × NPV.

Figure 5:

Graph shows volume (teal columns) and SSS (red columns) reduction at 12-month follow-up in four fibroid groups formed on the basis of NPV and SI immediately after MR-guided focused ultrasound surgery. b = P < .05 versus hypointense fibroids within the same NPV group.