title: Ultrasound image based visual servoing for moving target ablation by high intensity focused ultrasound.
abstract: BACKGROUND
  Although high intensity focused ultrasound (HIFU) is a promising technology for tumor treatment, a moving abdominal target is still a challenge in current HIFU systems. In particular, respiratory-induced organ motion can reduce the treatment efficiency and negatively influence the treatment result. In this research, we present: (1) a methodology for integration of ultrasound (US) image based visual servoing in a HIFU system; and (2) the experimental results obtained using the developed system.
  
  
  METHODS
  In the visual servoing system, target motion is monitored by biplane US imaging and tracked in real time (40 Hz) by registration with a preoperative 3D model. The distance between the target and the current HIFU focal position is calculated in every US frame and a three-axis robot physically compensates for differences. Because simultaneous HIFU irradiation disturbs US target imaging, a sophisticated interlacing strategy was constructed.
  
  
  RESULTS
  In the experiments, respiratory-induced organ motion was simulated in a water tank with a linear actuator and kidney-shaped phantom model. Motion compensation with HIFU irradiation was applied to the moving phantom model. Based on the experimental results, visual servoing exhibited a motion compensation accuracy of 1.7 mm (RMS) on average. Moreover, the integrated system could make a spherical HIFU-ablated lesion in the desired position of the respiratory-moving phantom model.
  
  
  CONCLUSIONS
  We have demonstrated the feasibility of our US image based visual servoing technique in a HIFU system for moving target treatment.
authors.affiliation: Korea Institute of Machinery and Materials, Daegu, South Korea.
authors.forename: Joonho
authors.initials: J
authors.lastname: Seo
authors.affiliation: The University of Electro Communications, Tokyo, Japan.
authors.forename: Norihiro
authors.initials: N
authors.lastname: Koizumi
authors.affiliation: The University of Tokyo, Tokyo, Japan.
authors.forename: Mamoru
authors.initials: M
authors.lastname: Mitsuishi
authors.affiliation: The University of Tokyo, Tokyo, Japan.
authors.forename: Naohiko
authors.initials: N
authors.lastname: Sugita
mesh_terms: D000005:Abdomen; D057086:High-Intensity Focused Ultrasound Ablation / Q000379:methods*; D006801:Humans; D021621:Imaging, Three-Dimensional; D007668:Kidney / Q000000981:diagnostic imaging*; D008099:Liver / Q000000981:diagnostic imaging*; D008113:Liver Neoplasms / Q000000981:diagnostic imaging* / Q000628:therapy*; D009038:Motion; D019047:Phantoms, Imaging; D012119:Respiration; D025321:Surgery, Computer-Assisted; D014463:Ultrasonography / Q000379:methods*; D014867:Water
chemical_list: D014867:Water
keywords: high intensity focused ultrasound; motion compensation; robotic HIFU; visual servoing