title: Heat sink phenomenon of bipolar and monopolar radiofrequency ablation observed using polypropylene tubes for vessel simulation.
abstract: BACKGROUND
  Radiofrequency ablation (RFA) is widely used for treating liver tumors; recurrence is common owing to proximity to blood vessels possibly due to the heat sink effect. We seek to investigate this phenomenon using unipolar and bipolar RFA on an egg white tumor tissue model and an animal liver model.
  
  
  METHODS
  Temperature profiles during ablation (with and without vessel simulation) were studied, using both bipolar and unipolar RFA probes by 4 strategically placed temperature leads to monitor temperature profile during ablation. The volume of ablated tissue was also measured.
  
  
  RESULTS
  The volume ablated during vessel simulation confirmed the impact of the heat sink phenomenon. The heat sink effect of unipolar RFA was greater compared with bipolar RFA (ratio of volume affected 2:1) in both tissue and liver models. The volume ablated using unipolar RFA was less than the bipolar RFA (ratio of volume ablated = 1:4). Unipolar RFA achieved higher ablation temperatures (122°C vs 98°C). Unipolar RFA resulted in tissue damage beyond the vessel, which was not observed using bipolar RFA.
  
  
  CONCLUSIONS
  Bipolar RFA ablates a larger tumor volume compared with unipolar RFA, with a single ablation. The impact of heat sink phenomenon in tumor ablation is less so with bipolar than unipolar RFA with sparing of adjacent vessel damage.
authors.affiliation: University of New South Wales, St George Hospital, Kogarah, New South Wales, Australia.
authors.forename: Ihssan
authors.initials: I
authors.lastname: Al-Alem
authors.affiliation: University of New South Wales, St George Hospital, Kogarah, New South Wales, Australia.
authors.forename: Krishna
authors.initials: K
authors.lastname: Pillai
authors.affiliation: University of New South Wales, St George Hospital, Kogarah, New South Wales, Australia.
authors.forename: Javed
authors.initials: J
authors.lastname: Akhter
authors.affiliation: University of New South Wales, St George Hospital, Kogarah, New South Wales, Australia.
authors.forename: Terence C
authors.initials: TC
authors.lastname: Chua
authors.affiliation: University of New South Wales, St George Hospital, Kogarah, New South Wales, Australia david.morris@unsw.edu.au.
authors.forename: David L
authors.initials: DL
authors.lastname: Morris
mesh_terms: D000818:Animals; D017115:Catheter Ablation / Q000009:adverse effects / Q000295:instrumentation* / Q000379:methods*; D002417:Cattle; D003198:Computer Simulation; D004529:Egg White / Q000528:radiation effects; D006358:Hot Temperature; D008099:Liver / Q000098:blood supply / Q000528:radiation effects; D008954:Models, Biological; D011126:Polypropylenes
chemical_list: D011126:Polypropylenes
keywords: simulation; surgical oncology; tissue engineering