title: Effect of nonparallel placement of in-circle bipolar radiofrequency ablation probes on volume of tissue ablated with heat sink.
abstract: OBJECTIVE
  Percutaneous bipolar radiofrequency ablation (RFA) is a minimally invasive technique for treating liver tumors. It is not always possible to insert the bipolar probes parallel to each other on either side of tumor, since it restricts maneuverability away from vital structures or ablate certain tumor shape. Therefore, we investigated how nonparallel placement of probes affected ablation.
  
  
  METHODS
  Bipolar RFA in parallel and in divergent positions were submerged in tissue model (800 mL egg white) at 37°C and ablated. Temperature probes, T1 and T2 were placed 8.00 mm below the tip of the probes, T3 in between the probe coil elements and T4 and T5 at water inlet and outlet, respectively. Both models with heat sink (+HS) and without (-HS) were investigated.
  
  
  RESULTS
  The mean ablated tissue volume, mass, density and height increased linearly with unit angle increase for -HS model. With +HS, a smaller increase in mean volume and mass, a slightly greater increase in mean density but a reduction in height of tissue was seen. The mean ablation time and duration of maximum temperature with +HS was slightly larger, compared with -HS, while -HS ablated at a slightly higher temperature. The heat sink present was minimal for probes in parallel position compared to nonparallel positions.
  
  
  CONCLUSIONS
  Divergence from parallel insertion of bipolar RFA probes increased the mean volume, mass, and density of tissue ablated. However, the presence of large heat sinks may limit the application of this technique, when tumors border on larger vessels.
authors: University of New South Wales, St. George Hospital, Kogarah, New South Wales, Australia panthera6444@yahoo.com.au.
authors: Krishna
authors: K
authors: Pillai
authors: University of New South Wales, St. George Hospital, Kogarah, New South Wales, Australia.
authors: Ihssan
authors: I
authors: Al-Alem
authors: University of New South Wales, St. George Hospital, Kogarah, New South Wales, Australia.
authors: Javed
authors: J
authors: Akhter
authors: University of New South Wales, St. George Hospital, Kogarah, New South Wales, Australia.
authors: Terence C
authors: TC
authors: Chua
authors: University of New South Wales, St. George Hospital, Kogarah, New South Wales, Australia.
authors: Mena
authors: M
authors: Shehata
authors: University of New South Wales, St. George Hospital, Kogarah, New South Wales, Australia.
authors: David L
authors: DL
authors: Morris
mesh_terms: D000818:Animals; D017115:Catheter Ablation / Q000295:instrumentation* / Q000379:methods*; D002645:Chickens; D004529:Egg White; D006358:Hot Temperature; D008954:Models, Biological
keywords: angular placement; heat sink; radiofrequency ablation; vessel simulation