title: MR thermometry analysis of sonication accuracy and safety margin of volumetric MR imaging-guided high-intensity focused ultrasound ablation of symptomatic uterine fibroids.
abstract: OBJECTIVE
  To 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.
  
  
  METHODS
  This 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.
  
  
  RESULTS
  Overall 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.
  
  
  CONCLUSIONS
  Sonication 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.
authors.affiliation: 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.
authors.forename: Young-sun
authors.initials: YS
authors.lastname: Kim
authors.forename: Hervé
authors.initials: H
authors.lastname: Trillaud
authors.forename: Hyunchul
authors.initials: H
authors.lastname: Rhim
authors.forename: Hyo K
authors.initials: HK
authors.lastname: Lim
authors.forename: Willem
authors.initials: W
authors.lastname: Mali
authors.forename: Marianne
authors.initials: M
authors.lastname: Voogt
authors.forename: Jörg
authors.initials: J
authors.lastname: Barkhausen
authors.forename: Thomas
authors.initials: T
authors.lastname: Eckey
authors.forename: Max O
authors.initials: MO
authors.lastname: Köhler
authors.forename: Bilgin
authors.initials: B
authors.lastname: Keserci
authors.forename: Charles
authors.initials: C
authors.lastname: Mougenot
authors.forename: Shunmugavelu D
authors.initials: SD
authors.lastname: Sokka
authors.forename: Jouko
authors.initials: J
authors.lastname: Soini
authors.forename: Heikki J
authors.initials: HJ
authors.lastname: Nieminen
mesh_terms: D000328:Adult; D005260:Female; D057086:High-Intensity Focused Ultrasound Ablation / Q000379:methods*; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods; D007889:Leiomyoma / Q000175:diagnosis / Q000601:surgery*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008875:Middle Aged; D011379:Prognosis; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D025321:Surgery, Computer-Assisted / Q000379:methods; D013817:Thermography / Q000379:methods*; D016896:Treatment Outcome; D014594:Uterine Neoplasms / Q000175:diagnosis / Q000601:surgery*