title: Magnetic resonance imaging-guided focused ultrasound surgery for symptomatic uterine fibroids: estimation of treatment efficacy using thermal dose calculations.
abstract: OBJECTIVE
  To study the correlation between the predicted thermal dose volume (TDV) and the actual ablation volumes in MR-guided focused ultrasound surgery (MRgFUS) for symptomatic uterine fibroids, and to follow up the outcome for 12 months post-treatment.
  
  
  METHODS
  Phase-difference fast spoiled gradient-echo MR images were used to analyze thermal change during the energy deliveries of MRgFUS in 60 consecutive patients treated for symptomatic uterine fibroids. The TDV obtained through analysis of these MR images was compared with the non-perfused volume (NPV) measured on post-treatment contrast enhanced T1-weighted images. Final values of TDV ratio and NPV ratio were obtained by dividing these values by original fibroid volume. Patients were followed for 12 months post-treatment to assess symptomatic relief using the symptom severity score (SSS).
  
  
  RESULTS
  Treatments in which we managed to reach a TDV ratio larger than 27% of the treated fibroid yielded a ratio of NPV to TDV of 1.1±0.5, indicating accurate control of the non-invasive procedure. Patient symptoms, as measured by the SSS, continuously decreased from a mean baseline score of 50±22 to 19±12 (P<0.0001) 12 months post-treatment.
  
  
  CONCLUSIONS
  At large treatment volumes (exceeding 27% TDV ratio), thermal dose estimates correspond very closely to non-perfused volumes measured immediately post treatment. These large treatment volumes result in continuous clinical improvement throughout the first 12 months after MRgFUS.
authors.affiliation: Department of Diagnostic Radiology, CHA Bundang Medical Center, CHA University, Republic of Korea. jansons@cha.ac.kr
authors.forename: Sang-Wook
authors.initials: SW
authors.lastname: Yoon
authors.forename: Sun Hee
authors.initials: SH
authors.lastname: Cha
authors.forename: Young Geon
authors.initials: YG
authors.lastname: Ji
authors.forename: Hyun Cheol
authors.initials: HC
authors.lastname: Kim
authors.forename: Mee Hwa
authors.initials: MH
authors.lastname: Lee
authors.forename: Jin Ho
authors.initials: JH
authors.lastname: Cho
mesh_terms: D000328:Adult; D005260:Female; D057086:High-Intensity Focused Ultrasound Ablation; D006801:Humans; D007889:Leiomyoma / Q000601:surgery*; D053783:Magnetic Resonance Imaging, Interventional; D008875:Middle Aged; D011829:Radiation Dosage; D012189:Retrospective Studies; D014594:Uterine Neoplasms / Q000601:surgery*
keywords: Focused ultrasound; Magnetic resonance imaging; Thermal ablation; Uterine fibroid