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Robotically Assisted Sonic Therapy (RAST) for Noninvasive Hepatic Ablation in a Porcine Model: Mitigation of Body Wall Damage with a Modified Pulse Sequence

  • Longo, Katherine C.1
  • Knott, Emily A.1
  • Watson, Rao F.2
  • Swietlik, John F.1
  • Vlaisavljevich, Eli3
  • Smolock, Amanda R.4
  • Xu, Zhen5
  • Cho, Clifford S.6
  • Mao, Lu7
  • Lee, Fred T. Jr.1, 8, 9
  • Ziemlewicz, Timothy J.1
  • 1 University of Wisconsin Hospital and Clinics, Department of Radiology, 600 Highland Ave, Madison, WI, 53705, USA , Madison (United States)
  • 2 University of Wisconsin, Department of Pathology, Madison, USA , Madison (United States)
  • 3 Virginia Polytechnic and State University, Department of Biomedical Engineering and Mechanics, Blacksburg, USA , Blacksburg (United States)
  • 4 University of Pennsylvania, Division of Interventional Radiology, Department of Radiology, Philadelphia, USA , Philadelphia (United States)
  • 5 University of Michigan, Department of Biomedical Engineering, Ann Arbor, USA , Ann Arbor (United States)
  • 6 University of Michigan, Department of Surgery, Ann Arbor, USA , Ann Arbor (United States)
  • 7 University of Wisconsin, Department of Biostatistics and Medical Informatics, Madison, USA , Madison (United States)
  • 8 University of Wisconsin, Department of Biomedical Engineering, Madison, USA , Madison (United States)
  • 9 University of Wisconsin, Department of Urology, Madison, USA , Madison (United States)
Published Article
CardioVascular and Interventional Radiology
Publication Date
Apr 30, 2019
DOI: 10.1007/s00270-019-02215-8
Springer Nature


PurposeRobotically assisted sonic therapy (RAST) is a nonthermal, noninvasive ablation method based on histotripsy. Prior animal studies have demonstrated the ability to create hepatic ablation zones at the focal point of an ultrasound therapy transducer; however, these treatments resulted in thermal damage to the body wall within the path of ultrasound energy delivery. The purpose of this study was to evaluate the efficacy and safety of a pulse sequence intended to mitigate prefocal body wall injury.Materials and MethodsHealthy swine (n = 6) underwent hepatic RAST (VortxRx software version, HistoSonics, Ann Arbor MI) in the right hepatic lobe. A 3.0 cm spherical ablation zone was prescribed for each. Following treatment, animals underwent MRI which was utilized for ablation zone measurement, evaluation of prefocal injury, and assessment of complications. Each animal was euthanized, underwent necropsy, and the tissue was processed for histopathologic analysis of the ablation zone and any other sites concerning for injury.ResultsNo prefocal injury was identified by MRI or necropsy in the body wall or tissues overlying the liver. Ablation zones demonstrated uniform cell destruction, were nearly spherical (sphericity index = 0.988), and corresponded closely to the prescribed size (3.0 × 3.1 × 3.4 cm, p = 0.70, 0.36, and 0.01, respectively). Ablation zones were associated with portal vein (n = 3, one occlusive) and hepatic vein thrombosis (n = 4, one occlusive); however, bile ducts remained patent within ablation zones (n = 2).ConclusionsHepatic RAST performed with a modified ultrasound pulse sequence in a porcine model can mitigate prefocal body wall injuries while maintaining treatment efficacy. Further study of hepatic RAST appears warranted, particularly in tumor models.

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