J. Louis Hinshaw MD, Abstract Co-Author: Research grant, Endocare, Inc

Winifred Leung MD, Presenter: Nothing to Disclose

Fred T. Lee MD, Abstract Co-Author: Stockholder, NeuWave Medical Inc, Madison, WI Patent holder, Covidien AG, Boulder, CO

Lisa Ann Sampson, Abstract Co-Author: Research Consultant, NeuWave Medical Inc

Nathan A. Durick MD, Abstract Co-Author: Nothing to Disclose

Christopher L. Brace PhD, Abstract Co-Author: Shareholder, NeuWave Medical Inc, Madison, WI Consultant, NeuWave Medical Inc, Madison, WI

As image-guided tumor ablation has developed, it has become clear that different tissues often require unique protocols to ensure optimal results. The purpose of this study was to establish the relative merits of a double freeze protocol as compared with a triple freeze protocol when performing pulmonary cryoablation utilizing an in vivo porcine lung model.

A total of 18 cryoablations were performed in normal porcine lung utilizing percutaneous technique. Ablation protocols were randomized to either a 10-5-10 minute double freeze-thaw cycle, or a 3-3-7-7-5 minute triple freeze-thaw protocol. During the ablation, non-contrast CT images were obtained at 3, 6, 10, 13, 16, 20, and 25 minutes. The evolution of the ablation zone on CT imaging was evaluated. The animals were sacrificed immediately after the ablation and the ablation zones were sectioned transverse to the insertion tract at 5 mm increments. The diameter, area, and circularity of each ablation zone was measured.  

There was earlier identification of the imaging findings with the triple freeze-thaw protocol (6 minutes vs. 13 minutes). Also, despite a shorter total freeze time (15 minutes vs. 20 minutes), the triple freeze-thaw protocol was associated with a nearly identical ablation as compared with the double freeze-thaw protocol (mean diameter: 1.67  1.41 cm vs. 1.66  2.13 cm, p = 0.77, area: 2.10  0.48 cm vs. 1.99  0.62 cm. p = 0.70, and circularity 0.95  0.04 vs. 0.96  0.03, p = 0.62, respectively).

This study suggests several advantages of a triple freeze-thaw protocol during pulmonary cryoablation including: earlier identification of the imaging findings associated with the ablation (may be advantageous for monitoring the ablation zone during the procedure); a nearly identical zone of necrosis with a shorter total freeze time (15 minutes vs. 20 minutes), which may ultimately result in decreased procedural time in the clinical setting; and possibly more effective cytotoxicity related to the additional freeze-thaw cycle.

This study identifies several advantages to utilizing a triple freeze-thaw protocol when performing pulmonary cryoablation and is a first step in determining an optimal protocol for this technique.

Hinshaw, J, Leung, W, Lee, F, Sampson, L, Durick, N, Brace, C, Pulmonary Cryoablation: A Triple Freeze-thaw Cycle Results in Earlier Identification of CT Imaging Changes and May Shorten Procedure Time.  Radiological Society of North America 2008 Scientific Assembly and Annual Meeting, February 18 - February 20, 2008 ,Chicago IL. http://archive.rsna.org/2008/6021337.html