title: MRI-based prediction of pulsed high-intensity focused ultrasound effect on tissue transport in rabbit muscle.
abstract: OBJECTIVE
  To design an algorithm for optimizing pulsed high intensity focused ultrasound (p-HIFU) treatment parameters to maximize tissue transport while minimizing thermal necrosis based on MR image guidance.
  
  
  METHODS
  P-HIFU power, duty cycle, and treatment duration were varied to generate different levels of thermal and mechanical deposition in rabbit muscle. Changes in T2-weighted and T1 contrast-enhanced (CE) signal were assessed immediately following treatment and at 24 h. Transport parameters were extracted by means of T1-weighted dynamic contrast-enhanced MRI (DCE-MRI) technique at 0 and 24-h time points.
  
  
  RESULTS
  Successful p-HIFU treatment was indicated by focal hyperintensity on the T2-weighted image immediately post-treatment, suggesting increased fluid (edema), with little intensity change in CE image. After 24 h, the affected region expanded along the muscle fiber accompanied by clear hyperintensity in CE image (contrast uptake). Quantitative DCE-MRI analysis revealed statistically significant increases in both leakage rate and extracellular space, accompanied by a decrease in clearance rate.
  
  
  CONCLUSIONS
  Successful p-HIFU treatment was mainly correlated to tissue heating. Tissue transport properties following treatment success would result in improved contact between drug and targets in both time and space. MRI is the key to controlling treatment by means of thermometry and also monitoring efficacy by means of T2-weighted imaging.
authors.affiliation: Department of Translational Imaging, The Methodist Hospital Research Institute, Houston, Texas, USA.
authors.forename: Brian E
authors.initials: BE
authors.lastname: O'Neill
authors.forename: Howard Q
authors.initials: HQ
authors.lastname: Vo
authors.forename: Hongwei
authors.initials: H
authors.lastname: Shao
authors.forename: Christof
authors.initials: C
authors.lastname: Karmonik
authors.forename: Xiaobo
authors.initials: X
authors.lastname: Zhou
authors.forename: King C
authors.initials: KC
authors.lastname: Li
mesh_terms: D000465:Algorithms; D000818:Animals; D001831:Body Temperature; D005260:Female; D057086:High-Intensity Focused Ultrasound Ablation / Q000379:methods*; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D018482:Muscle, Skeletal / Q000473:pathology / Q000503:physiopathology* / Q000601:surgery*; D011817:Rabbits; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D025321:Surgery, Computer-Assisted / Q000379:methods*; D013814:Thermal Conductivity; D016896:Treatment Outcome
keywords: MRI-guided focused ultrasound; clearance rate; drug delivery; dynamic contrast enhanced-MRI; pulsed high-intensity focused ultrasound; tissue permeability
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