title: Factors affecting tumor ablation during high intensity focused ultrasound treatment.
abstract: OBJECTIVE
  High intensity focused ultrasound (HIFU) utilizes a targeted extracorporeal focused ultrasound beam to ablate neoplastic pancreatic tissue. We used an in vitro model to examine the effects of bone, metallic stents, plastic stents, metal plates, and cyst-like lesions on HIFU treatment.
  
  
  METHODS
  HIFU was delivered to the phantom models implanted with foreign bodies, and the location, shape, and size of the ablated zones were evaluated.
  
  
  RESULTS
  Bone and metallic plates reflected the ultrasound beam, shifting the ablation zone from the focal zone to the prefocal area. In the phantoms containing metal stent, plastic stent, and cyst, most of the ablative energy was reflected to the prefocal area by the surface, with the remainder penetrating through the phantom. The area of the ablated margins was significantly larger in size and volume than the intended focal ablation zone.
  
  
  CONCLUSIONS
  During HIFU therapy, artificial or anatomical barriers could affect the direction of the ultrasound beams, shifting the ablation zone from the focal area to a prefocal site with a larger than expected ablation zone. These factors should be considered prior to HIFU treatment for pancreatic tumors because they could limit ablation success, in addition to causing complications.
authors: Division of Gastroenterology, Department of Internal Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors: Aizan
authors: A
authors: Hassanuddin
authors: Division of Gastroenterology, Department of Internal Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors: Jun-Ho
authors: JH
authors: Choi
authors: Division of Gastroenterology, Department of Internal Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors: Dong-Wan
authors: DW
authors: Seo
authors: Division of Gastroenterology, Department of Internal Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors: Choong Heon
authors: CH
authors: Ryu
authors: Asan Institute for Life Sciences, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors: Su-Hui
authors: SH
authors: Kim
authors: Division of Gastroenterology, Department of Internal Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors: Do Hyun
authors: DH
authors: Park
authors: Division of Gastroenterology, Department of Internal Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors: Sang Soo
authors: SS
authors: Lee
authors: Division of Gastroenterology, Department of Internal Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors: Sung Koo
authors: SK
authors: Lee
authors: Division of Gastroenterology, Department of Internal Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors: Myung-Hwan
authors: MH
authors: Kim
mesh_terms: D000230:Adenocarcinoma / Q000628:therapy*; D057086:High-Intensity Focused Ultrasound Ablation / Q000379:methods*; D006801:Humans; D008953:Models, Anatomic; D010190:Pancreatic Neoplasms / Q000628:therapy*; D019047:Phantoms, Imaging; D015607:Stents
keywords: Cysts; High-intensity focused ultrasound ablation; Metal stent; Phantom