title: Optimal imaging of in vitro clot sonothrombolysis by MR-guided focused ultrasound.
abstract: OBJECTIVE
  As magnetic resonance-guided focused ultrasound (MRgFUS) sonothrombolysis relies on mechanical rather than thermal mechanisms to achieve clot lysis, thermometry is not useful for the intraoperative monitoring of clot breakdown by MRgFUS. Therefore, the purpose of this study was to evaluate the optimum imaging sequence for sonothrombolysis.
  
  
  METHODS
  In vitro blood drawn from 6 healthy volunteers was imaged using T1, T2 spin-echo, and T2 gradient-echo (GRE) sequences both before and after sonication using an Insightec ExAblate 4000 FUS transducer. Signal intensities of the three MR imaging sequences were measured and normalized to background signal for each time point. Representative samples of the pre- and postsonication clot were also sent to pathology for hematologic analysis.
  
  
  RESULTS
  After sonication, the clot in the treatment tube was fully lysed as evidenced by physical and hematologic evaluation. The difference between pre- and postsonicated normalized signal intensity ratios demonstrated statistical significance only on T2 and GRE sequences (P < .001). However, significant blooming artifact limited interpretation on all GRE images.
  
  
  CONCLUSIONS
  T2 is the most appropriate sequence for the evaluation of mechanical MRgFUS sonothrombolysis of an in vitro clot. These findings are consistent across the oxidative states of clot up to 48 hours.
authors.affiliation: Department of Radiology, University of Virginia, Charlottesville, VA, USA.
authors.forename: Christopher
authors.initials: C
authors.lastname: Durst
authors.forename: Stephen
authors.initials: S
authors.lastname: Monteith
authors.forename: Jason
authors.initials: J
authors.lastname: Sheehan
authors.forename: Krisztina
authors.initials: K
authors.lastname: Moldovan
authors.forename: John
authors.initials: J
authors.lastname: Snell
authors.forename: Matt
authors.initials: M
authors.lastname: Eames
authors.forename: Thomas
authors.initials: T
authors.lastname: Huerta
authors.forename: William
authors.initials: W
authors.lastname: Walker
authors.forename: Francesco
authors.initials: F
authors.lastname: Viola
authors.forename: Neal
authors.initials: N
authors.lastname: Kassell
authors.forename: Max
authors.initials: M
authors.lastname: Wintermark
mesh_terms: D000465:Algorithms; D001769:Blood / Q000528:radiation effects; D001777:Blood Coagulation / Q000528:radiation effects*; D057086:High-Intensity Focused Ultrasound Ablation / Q000379:methods*; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D016247:Information Storage and Retrieval / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods*; D061185:Mechanical Thrombolysis / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D025321:Surgery, Computer-Assisted / Q000379:methods*; D016896:Treatment Outcome