title: Localised hyperthermia in rodent models using an MRI-compatible high-intensity focused ultrasound system.
abstract: OBJECTIVE
  Localised hyperthermia in rodent studies is challenging due to the small target size. This study describes the development and characterisation of an MRI-compatible high-intensity focused ultrasound (HIFU) system to perform localised mild hyperthermia treatments in rodent models.
  
  
  METHODS
  The hyperthermia platform consisted of an MRI-compatible small animal HIFU system, focused transducers with sector-vortex lenses, a custom-made receive coil, and means to maintain systemic temperatures of rodents. The system was integrated into a 3T MR imager. Control software was developed to acquire images, process temperature maps, and adjust output power using a proportional-integral-derivative feedback control algorithm. Hyperthermia exposures were performed in tissue-mimicking phantoms and in a rodent model (n = 9). During heating, an ROI was assigned in the heated region for temperature control and the target temperature was 42 °C; 30 min mild hyperthermia treatment followed by a 10-min cooling procedure was performed on each animal.
  
  
  RESULTS
  3D-printed sector-vortex lenses were successful at creating annular focal regions which enables customisation of the heating volume. Localised mild hyperthermia performed in rats produced a mean ROI temperature of 42.1 ± 0.3 °C. The T10 and T90 percentiles were 43.2 ± 0.4 °C and 41.0 ± 0.3 °C, respectively. For a 30-min treatment, the mean time duration between 41-45 °C was 31.1 min within the ROI.
  
  
  CONCLUSIONS
  The MRI-compatible HIFU system was successfully adapted to perform localised mild hyperthermia treatment in rodent models. A target temperature of 42 °C was well-maintained in a rat thigh model for 30 min.
authors.affiliation: a Department of Radiology , University of Texas Southwestern Medical Center , Dallas , Texas .
authors.forename: Chenchen
authors.initials: C
authors.lastname: Bing
authors.affiliation: a Department of Radiology , University of Texas Southwestern Medical Center , Dallas , Texas .
authors.forename: Joris
authors.initials: J
authors.lastname: Nofiele
authors.affiliation: a Department of Radiology , University of Texas Southwestern Medical Center , Dallas , Texas .|b Clinical Sites Research Program, Philips Research , Briarcliff Manor , New York .
authors.forename: Robert
authors.initials: R
authors.lastname: Staruch
authors.affiliation: a Department of Radiology , University of Texas Southwestern Medical Center , Dallas , Texas .
authors.forename: Michelle
authors.initials: M
authors.lastname: Ladouceur-Wodzak
authors.affiliation: c Applied Research Center, University of Texas at Dallas , Dallas , Texas .
authors.forename: Yonatan
authors.initials: Y
authors.lastname: Chatzinoff
authors.affiliation: d Center of Veterinary Health Sciences, Oklahoma State University , Stillwater , Oklahoma , USA , and.
authors.forename: Ashish
authors.initials: A
authors.lastname: Ranjan
authors.affiliation: a Department of Radiology , University of Texas Southwestern Medical Center , Dallas , Texas .|e Advanced Imaging Research Center, University of Texas Southwestern Medical Center , Dallas , Texas.
authors.forename: Rajiv
authors.initials: R
authors.lastname: Chopra
mesh_terms: D000818:Animals; D004867:Equipment Design; D057086:High-Intensity Focused Ultrasound Ablation / Q000295:instrumentation; D006979:Hyperthermia, Induced; D008279:Magnetic Resonance Imaging; D008297:Male; D023421:Models, Animal; D019047:Phantoms, Imaging; D017207:Rats, Sprague-Dawley; D012984:Software
keywords: Heat-targeted drug delivery; MR-HIFU; mild hyperthermia; nanoparticles; non-invasive thermometry