title: Respiration based steering for high intensity focused ultrasound liver ablation.
abstract: OBJECTIVE
  Respiratory motion makes hepatic ablation using high intensity focused ultrasound (HIFO) challenging. Previous HIFU liver treatment had required apnea induced during general anesthesia. We describe and test a system that allows treatment of the liver in the presence of breathing motion.
  
  
  METHODS
  Mapping a signal from an external respiratory bellow to treatment locations within the liver allows the ultrasound transducer to be steered in real time to the target location. Using a moving phantom, three metrics were used to compare static, steered, and unsteered sonications: the area of sonications once a temperature rise of 15°C was achieved, the energy deposition required to reach that temperature, and the average rate of temperature rise during the first 10 s of sonication. Steered HIFU in vivo ablations of the porcine liver were also performed and compared to breath-hold ablations.
  
  
  RESULTS
  For the last phantom metric, all groups were found to be statistically significantly different (P ≤ 0.003). However, in the other two metrics, the static and unsteered sonications were not statistically different (P > 0.9999). Steered in vivo HIFU ablations were not statistically significantly different from ablations during breath-holding.
  
  
  CONCLUSIONS
  A system for performing HIFU steering during ablation of the liver with breathing motion is presented and shown to achieve results equivalent to ablation performed with breath-holding.
authors: Department of Radiology, Stanford University, Stanford, California, USA.
authors: Andrew B
authors: AB
authors: Holbrook
authors: Pejman
authors: P
authors: Ghanouni
authors: Juan M
authors: JM
authors: Santos
authors: Charles
authors: C
authors: Dumoulin
authors: Yoav
authors: Y
authors: Medan
authors: Kim Butts
authors: KB
authors: Pauly
mesh_terms: D000818:Animals; D016477:Artifacts; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006498:Hepatectomy / Q000295:instrumentation / Q000379:methods; D057086:High-Intensity Focused Ultrasound Ablation / Q000295:instrumentation / Q000379:methods*; D008099:Liver / Q000473:pathology / Q000601:surgery*; D008279:Magnetic Resonance Imaging / Q000295:instrumentation / Q000379:methods*; D019047:Phantoms, Imaging; D015656:Respiratory Mechanics; D055425:Respiratory-Gated Imaging Techniques / Q000295:instrumentation / Q000379:methods*; D025321:Surgery, Computer-Assisted / Q000295:instrumentation / Q000379:methods*; D013552:Swine; D016896:Treatment Outcome