title: Volumetric MRI-guided high-intensity focused ultrasound for noninvasive, in vivo determination of tissue thermal conductivity: initial experience in a pig model.
abstract: OBJECTIVE
  To estimate the local thermal conductivity of porcine thigh muscle at temperatures required for magnetic resonance imaging (MRI)-guided high-intensity focused ultrasound (MRgHIFU) surgery (60-90°C).
  
  
  METHODS
  Using MRgHIFU, we performed 40 volumetric ablations in the thigh muscles of four pigs. Thirty-five of the sonications were successful. We used MRI to monitor the resulting temperature increase. We then determined local thermal conductivity by analyzing the spatiotemporal spread of temperature during the cooling period.
  
  
  RESULTS
  The thermal conductivity of MRgHIFU-treated porcine thigh muscle fell within a narrow range (0.52 ± 0.05 W/[m*K]), which is within the range reported for porcine thigh muscle at temperatures of <40°C (0.52 to 0.62 W/[m*K]). Thus, there was little change in the thermal conductivity of porcine thigh muscle at temperatures required for MRgHIFU surgery compared to lower temperatures.
  
  
  CONCLUSIONS
  Our MRgHIFU-based approach allowed us to estimate, with good reproducibility, the local thermal conductivity of in vivo deep tissue in real time at temperatures of 60°C to 90°C. Therefore, our method provides a valuable tool for quantifying the influence of thermal conductivity on temperature distribution in tissues and for optimizing thermal dose delivery during thermal ablation with clinical MRgHIFU.
authors.affiliation: Physics Department and Texas Center for Superconductivity at the University of Houston, Houston, Texas, USA.
authors.forename: Jiming
authors.initials: J
authors.lastname: Zhang
authors.forename: Charles
authors.initials: C
authors.lastname: Mougenot
authors.forename: Ari
authors.initials: A
authors.lastname: Partanen
authors.forename: Raja
authors.initials: R
authors.lastname: Muthupillai
authors.forename: Pei-Herng
authors.initials: PH
authors.lastname: Hor
mesh_terms: D000818:Animals; D057086:High-Intensity Focused Ultrasound Ablation / Q000379:methods*; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D053783:Magnetic Resonance Imaging, Interventional / Q000379:methods*; D018482:Muscle, Skeletal / Q000601:surgery; D015203:Reproducibility of Results; D013552:Swine; D013814:Thermal Conductivity; D013848:Thigh