Kiran Sekhar, Presenter: Nothing to Disclose

Jennifer Shih BS, Abstract Co-Author: Nothing to Disclose

Alfred Luk BS, Abstract Co-Author: Nothing to Disclose

Pretesh Patel, Abstract Co-Author: Nothing to Disclose

Bradford Johns Wood MD, Abstract Co-Author: Researcher, Koninklijke Philips Electronics NV Researcher, Celsion Corporation Advisory Board, Koninklijke Philips Electronics NV Advisory Board, Tyco Healthcare (Valleylab)

Dieter Haemmerich PhD, Abstract Co-Author: Shareholder, Micrablate LLC

Radiofrequency ablation causes instant coagulation necrosis in tissues at temperatures greater than 60 degrees Celsius. With current systems using near 500kHz, the ablation deposits similar energy in both tumor and normal tissue. Computational heat transfer models suggest that at low frequencies (below 100kHz), tumor tissue can be preferentially heated compared to normal, non-cancerous tissue. This could cause less collateral damage and preserve normal tissue and function. A low frequency generator prototype was developed based upon the modeling, to investigate further this possibility

Transparent, bis-acrylimide gel, which allowed visualization of ablation processes, and ex-vivo cow liver were used to compare the commercial device (Radionics; Boulder, CO) to the prototype low frequency generator, to characterize ablation and electrical parameters. Both systems utilized a 3cm, active tip RFA electrode (Valleylab: Boulder, CO) for 15 minute ablations. Electrical parameters were manipulated to determine ablative properties for the low frequency generator and to normalize power with reference to the commercial generator.

In gel phantom and liver experiments, the low frequency generator was able to cause significant ablation above 16 watts. In addition the temperature reached by the low frequency unit was not dissimilar to the temperature generated by the commercial unit. Study groups included cooled and un-cooled electrodes. The low frequency generator caused ablation with 1 amp with a non-cooled electrode and with 1.7 amp for a cooled electrode. Sizes of ablation were similar between the two groups with non-cooled electrodes, as visualized by dissection.

The low frequency generator is able to heat and ablate gel and ex-vivo liver causing similar architectural changes and temperatures as a commercial unit. Further small animal in vivo studies are planned to evaluate the low frequency system theoretical advantage of selective ablation of cancerous tissue.

Low frequency radiofrequency ablation is feasible and could utilize intrinsic tumor properties to selectively heat tumor tissue and preserve the surrounding normal, functional tissue.

Sekhar, K, Shih, J, Luk, A, Patel, P, Wood, B, Haemmerich, D, Low Frequency Radiofrequency Ablation: Early Theory and Prototype to Selectively Ablate Tumor and Spare Normal Tissue.  Radiological Society of North America 2007 Scientific Assembly and Annual Meeting, November 25 - November 30, 2007 ,Chicago IL. http://archive.rsna.org/2007/5016283.html