title: Drift correction for accurate PRF-shift MR thermometry during mild hyperthermia treatments with MR-HIFU.
abstract: There is growing interest in performing hyperthermia treatments with clinical magnetic resonance imaging-guided high-intensity focused ultrasound (MR-HIFU) therapy systems designed for tissue ablation. During hyperthermia treatment, however, due to the narrow therapeutic window (41-45 °C), careful evaluation of the accuracy of proton resonant frequency (PRF) shift MR thermometry for these types of exposures is required.
  
  
  
  The purpose of this study was to evaluate the accuracy of MR thermometry using a clinical MR-HIFU system equipped with a hyperthermia treatment algorithm.
  
  
  
  Mild heating was performed in a tissue-mimicking phantom with implanted temperature sensors using the clinical MR-HIFU system. The influence of image-acquisition settings and post-acquisition correction algorithms on the accuracy of temperature measurements was investigated. The ability to achieve uniform heating for up to 40 min was evaluated in rabbit experiments.
  
  
  
  Automatic centre-frequency adjustments prior to image-acquisition corrected the image-shifts in the order of 0.1 mm/min. Zero- and first-order phase variations were observed over time, supporting the use of a combined drift correction algorithm. The temperature accuracy achieved using both centre-frequency adjustment and the combined drift correction algorithm was 0.57° ± 0.58 °C in the heated region and 0.54° ± 0.42 °C in the unheated region.
  
  
  
  Accurate temperature monitoring of hyperthermia exposures using PRF shift MR thermometry is possible through careful implementation of image-acquisition settings and drift correction algorithms. For the evaluated clinical MR-HIFU system, centre-frequency adjustment eliminated image shifts, and a combined drift correction algorithm achieved temperature measurements with an acceptable accuracy for monitoring and controlling hyperthermia exposures.
authors.affiliation: a Department of Radiology , University of Texas Southwestern Medical Center , Dallas , Texas , USA ;
authors.forename: Chenchen
authors.initials: C
authors.lastname: Bing
authors.affiliation: a Department of Radiology , University of Texas Southwestern Medical Center , Dallas , Texas , USA ;|c Clinical Sites Research Program, Philips Research , Cambridge , Massachusetts , USA ;
authors.forename: Robert M
authors.initials: RM
authors.lastname: Staruch
authors.affiliation: e Philips Healthcare , Vantaa , Finland ;
authors.forename: Matti
authors.initials: M
authors.lastname: Tillander
authors.affiliation: e Philips Healthcare , Vantaa , Finland ;
authors.forename: Max O
authors.initials: MO
authors.lastname: Köhler
authors.affiliation: d Philips Healthcare , Toronto , ON , Canada ;
authors.forename: Charles
authors.initials: C
authors.lastname: Mougenot
authors.affiliation: e Philips Healthcare , Vantaa , Finland ;
authors.forename: Mika
authors.initials: M
authors.lastname: Ylihautala
authors.affiliation: f Department of Pediatrics , University of Texas Southwestern Medical Center , Dallas , Texas , USA ;|g Pauline Allen Gill Center for Cancer and Blood Disorders, Children's Health System of Texas , Dallas , Texas , USA.
authors.forename: Theodore W
authors.initials: TW
authors.lastname: Laetsch
authors.affiliation: a Department of Radiology , University of Texas Southwestern Medical Center , Dallas , Texas , USA ;|b Advanced Imaging Research Center, University of Texas Southwestern Medical Center , Dallas , Texas , USA ;
authors.forename: Rajiv
authors.initials: R
authors.lastname: Chopra
mesh_terms: D000818:Animals; D005260:Female; D057086:High-Intensity Focused Ultrasound Ablation; D006979:Hyperthermia, Induced; D008279:Magnetic Resonance Imaging; D009369:Neoplasms / Q000000981:diagnostic imaging / Q000601:surgery / Q000628:therapy; D011817:Rabbits; D062125:Thermometry
keywords: MR-HIFU; Mild hyperthermia; PRF-shift MR thermometry; phase drift