title: Focal hepatic ablation using interstitial photon radiation energy.
abstract: BACKGROUND
  Intratumoral ablative therapy is being used increasingly for the treatment of primary and secondary hepatic malignancies. The interstitial point-source photon radiosurgery system (PRS) is a novel ablative technique that uses radiation therapy similar in dosimetry to interstitial brachytherapy.
  
  
  METHODS
  To determine the feasibility, toxicity, and local tissue destructive capabilities of the PRS in the liver, preliminary studies in a nontumor-bearing canine model were examined. A 6-month survival study was conducted. Each animal received three radiation treatments, in the right, central, and left hepatic regions. Three low-dose treatments were delivered to each of six animals (group A), generating a 2.0-cm-diameter radiated sphere with a dose of 20 Gy at the lesion edge. Three high-dose treatments were delivered to each of six animals (group B), generating a 3.0-cm-diameter radiated sphere with 20 Gy at the lesion edge.
  
  
  RESULTS
  The treatment reproducibly generated sharply demarcated hepatic ablative lesions proportional to the administered dose. Mean lesion diameter at 1 month was 1.6+/-0.2 cm in group A and 3.4+/-1.0 cm in group B. Lesion size was independent of intrahepatic location, including near vascular structures. PRS therapy, when applied to portal structures, resulted in hilar damage. Hilar damage appeared to be associated with arteriolar thrombosis and bile duct injury. Treatment of regions adjacent to large hepatic veins and the IVC was not associated with vessel thrombosis or stricture.
  
  
  CONCLUSIONS
  PRS ablation is a generally well-tolerated method that results in consistent, well-demarcated, symmetric lesions of complete necrosis with minimal adjacent parenchymal injury. Application of such an approach for the treatment of liver tumors is promising.
authors.affiliation: Department of Surgery, The Johns Hopkins University School of Medicine, Baltimore, MD, USA.
authors.forename: L G
authors.initials: LG
authors.lastname: Koniaris
authors.forename: D Y
authors.initials: DY
authors.lastname: Chan
authors.forename: C
authors.initials: C
authors.lastname: Magee
authors.forename: S B
authors.initials: SB
authors.lastname: Solomon
authors.forename: J H
authors.initials: JH
authors.lastname: Anderson
authors.forename: D O
authors.initials: DO
authors.lastname: Smith
authors.forename: T
authors.initials: T
authors.lastname: De Weese
authors.forename: L R
authors.initials: LR
authors.lastname: Kavoussi
authors.forename: M A
authors.initials: MA
authors.lastname: Choti
mesh_terms: D000818:Animals; D001160:Arterioles / Q000528:radiation effects; D001653:Bile Ducts, Intrahepatic / Q000528:radiation effects; D004195:Disease Models, Animal; D004285:Dogs; D004307:Dose-Response Relationship, Radiation; D004867:Equipment Design; D005240:Feasibility Studies; D005260:Female; D006503:Hepatic Veins / Q000528:radiation effects; D008099:Liver / Q000098:blood supply / Q000528:radiation effects / Q000601:surgery*; D008113:Liver Neoplasms / Q000601:surgery; D017785:Photons; D011833:Radiation Injuries, Experimental / Q000209:etiology; D016634:Radiosurgery / Q000009:adverse effects / Q000295:instrumentation / Q000379:methods*; D011879:Radiotherapy Dosage; D015203:Reproducibility of Results; D015996:Survival Rate; D013927:Thrombosis / Q000209:etiology; D014682:Vena Cava, Inferior / Q000528:radiation effects