Uterine fibroids: postsonication temperature decay rate enables prediction of therapeutic responses to MR imaging-guided high-intensity focused ultrasound ablation.
OBJECTIVE
To determine whether intraprocedural thermal parameters as measured with magnetic resonance (MR) thermometry can be used to predict immediate or delayed therapeutic response after MR-guided high-intensity focused ultrasound (HIFU) ablation of uterine fibroids.


METHODS
Institutional review board approval and subject informed consent were obtained. A total of 105 symptomatic uterine fibroids (mean diameter, 8.0 cm; mean volume, 251.8 mL) in 71 women (mean age, 43.3 years; age range, 25-52 years) who underwent volumetric MR HIFU ablation were analyzed. Correlations between tumor-averaged intraprocedural thermal parameters (peak temperature, thermal dose efficiency [estimated volume of 240 equivalent minutes at 43°C divided by volume of treatment cells], and temperature decay rate after sonication) and the immediate ablation efficiency (ratio of nonperfused volume [NPV] at immediate follow-up to treatment cell volume) or ablation sustainability (ratio of NPV at 3-month follow-up to NPV at immediate follow-up) were assessed with linear regression analysis.


RESULTS
A total of 2818 therapeutic sonications were analyzed. At immediate follow-up with MR imaging (n = 105), mean NPV-to-fibroid volume ratio and ablation efficiency were 0.68 ± 0.26 (standard deviation) and 1.35 ± 0.75, respectively. A greater thermal dose efficiency (B = 1.894, P < .001) and slower temperature decay rate (B = -1.589, P = .044) were independently significant factors that indicated better immediate ablation efficiency. At 3-month follow-up (n = 81), NPV had decreased to 43.1% ± 21.0 of the original volume, and only slower temperature decay rate was significantly associated with better ablation sustainability (B = -0.826, P = .041).


CONCLUSIONS
The postsonication temperature decay rate enables prediction of both immediate and delayed therapeutic responses, whereas thermal dose efficiency enables prediction of immediate therapeutic response to MR HIFU ablation of uterine fibroids.
From the Department of Radiology and Center for Imaging Science, Samsung Medical Center, Sungkyunkwan University School of Medicine, 50 Irwon-dong, Gangnam-gu, Seoul 138-225, Korea (Y.S.K., M.J.P., H.R., H.K.L.); Philips Healthcare, Seoul, Korea (B.K.); and Philips Healthcare, Vantaa, Finland (K.N., M.O.K.).
Young-sun
YS
Kim
Min Jung
MJ
Park
Bilgin
B
Keserci
Kirsi
K
Nurmilaukas
Max O
MO
Köhler
Hyunchul
H
Rhim
Hyo Keun
HK
Lim
D000328:Adult; D005260:Female; D057086:High-Intensity Focused Ultrasound Ablation; D006801:Humans; D007889:Leiomyoma / Q000601:surgery*; D053783:Magnetic Resonance Imaging, Interventional; D008875:Middle Aged; D011237:Predictive Value of Tests; D025321:Surgery, Computer-Assisted; D016896:Treatment Outcome; D014594:Uterine Neoplasms / Q000601:surgery*