• Young-sun Kim, Hervé Trillaud, Hyunchul Rhim, Hyo K Lim, Willem Mali, Marianne Voogt, Jörg Barkhausen, Thomas Eckey, Max O Köhler, Bilgin Keserci, Charles Mougenot, Shunmugavelu D Sokka, Jouko Soini, and Heikki J Nieminen.
• 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.
• Radiology. 2012 Nov 1;265(2):627-37.

PurposeTo evaluate the accuracy of the size and location of the ablation zone produced by volumetric magnetic resonance (MR) imaging-guided high-intensity focused ultrasound ablation of uterine fibroids on the basis of MR thermometric analysis and to assess the effects of a feedback control technique.Materials And MethodsThis prospective study was approved by the institutional review board, and written informed consent was obtained. Thirty-three women with 38 uterine fibroids were treated with an MR imaging-guided high-intensity focused ultrasound system capable of volumetric feedback ablation. Size (diameter times length) and location (three-dimensional displacements) of each ablation zone induced by 527 sonications (with [n=471] and without [n=56] feedback) were analyzed according to the thermal dose obtained with MR thermometry. Prospectively defined acceptance ranges of targeting accuracy were ±5 mm in left-right (LR) and craniocaudal (CC) directions and ±12 mm in anteroposterior (AP) direction. Effects of feedback control in 8- and 12-mm treatment cells were evaluated by using a mixed model with repeated observations within patients.ResultsOverall mean sizes of ablation zones produced by 4-, 8-, 12-, and 16-mm treatment cells (with and without feedback) were 4.6 mm±1.4 (standard deviation)×4.4 mm±4.8 (n=13), 8.9 mm±1.9×20.2 mm±6.5 (n=248), 13.0 mm±1.2×29.1 mm±5.6 (n=234), and 18.1 mm±1.4×38.2 mm±7.6 (n=32), respectively. Targeting accuracy values (displacements in absolute values) were 0.9 mm±0.7, 1.2 mm±0.9, and 2.8 mm±2.2 in LR, CC, and AP directions, respectively. Of 527 sonications, 99.8% (526 of 527) were within acceptance ranges. Feedback control had no statistically significant effect on targeting accuracy or ablation zone size. However, variations in ablation zone size were smaller in the feedback control group.ConclusionSonication accuracy of volumetric MR imaging-guided high-intensity focused ultrasound ablation of uterine fibroids appears clinically acceptable and may be further improved by feedback control to produce more consistent ablation zones.© RSNA, 2012

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