title: Toward real-time availability of 3D temperature maps created with temporally constrained reconstruction.
abstract: OBJECTIVE
  To extend the previously developed temporally constrained reconstruction (TCR) algorithm to allow for real-time availability of three-dimensional (3D) temperature maps capable of monitoring MR-guided high intensity focused ultrasound applications.
  
  
  METHODS
  A real-time TCR (RT-TCR) algorithm is developed that only uses current and previously acquired undersampled k-space data from a 3D segmented EPI pulse sequence, with the image reconstruction done in a graphics processing unit implementation to overcome computation burden. Simulated and experimental data sets of HIFU heating are used to evaluate the performance of the RT-TCR algorithm.
  
  
  RESULTS
  The simulation studies demonstrate that the RT-TCR algorithm has subsecond reconstruction time and can accurately measure HIFU-induced temperature rises of 20°C in 15 s for 3D volumes of 16 slices (RMSE = 0.1°C), 24 slices (RMSE = 0.2°C), and 32 slices (RMSE = 0.3°C). Experimental results in ex vivo porcine muscle demonstrate that the RT-TCR approach can reconstruct temperature maps with 192 × 162 × 66 mm 3D volume coverage, 1.5 × 1.5 × 3.0 mm resolution, and 1.2-s scan time with an accuracy of ±0.5°C.
  
  
  CONCLUSIONS
  The RT-TCR algorithm offers an approach to obtaining large coverage 3D temperature maps in real-time for monitoring MR-guided high intensity focused ultrasound treatments.
authors.affiliation: Department of Radiology, University of Utah, Salt Lake City, Utah, USA.
authors.forename: Nick
authors.initials: N
authors.lastname: Todd
authors.forename: Jaya
authors.initials: J
authors.lastname: Prakash
authors.forename: Henrik
authors.initials: H
authors.lastname: Odéen
authors.forename: Josh
authors.initials: J
authors.lastname: de Bever
authors.forename: Allison
authors.initials: A
authors.lastname: Payne
authors.forename: Phaneendra
authors.initials: P
authors.lastname: Yalavarthy
authors.forename: Dennis L
authors.initials: DL
authors.lastname: Parker
mesh_terms: D000465:Algorithms; D000818:Animals; D003199:Computer Systems; D057086:High-Intensity Focused Ultrasound Ablation / Q000379:methods*; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D066298:In Vitro Techniques; D008279:Magnetic Resonance Imaging / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D025321:Surgery, Computer-Assisted / Q000379:methods*; D013552:Swine; D013817:Thermography / Q000379:methods*
keywords: HIFU; MR thermometry; constrained reconstruction; temperature