Anna Moreland MD, Presenter: Consultant, NeuWave Medical, Inc

Meghan G. Lubner MD, Abstract Co-Author: Nothing to Disclose

Timothy J. Ziemlewicz MD, Abstract Co-Author: Nothing to Disclose

J. Louis Hinshaw MD, Abstract Co-Author: Stockholder, NeuWave Medical Inc Medical Advisory Board, NeuWave Medical Inc Stockholder, Cellectar Biosciences, Inc

Douglas Robert Kitchin MD, Abstract Co-Author: Nothing to Disclose

Alex Johnson, Abstract Co-Author: Nothing to Disclose

Fred T. Lee MD, Abstract Co-Author: Stockholder, NeuWave Medical, Inc Patent holder, NeuWave Medical, Inc Board of Directors, NeuWave Medical, Inc Patent holder, Covidien AG Inventor, Covidien AG Royalties, Covidien AG

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

Hydrodissection is an important technique to protect non-target structures during thermal ablation, but is hampered by the mobility of injected fluid. This study evaluated whether a thermoreversible poloxamer P407 (liquid at room temperature, gel at body temperature) can protect the diaphragm, body wall, and bowel adjacent to large microwave (MW) ablation zones in a porcine model.

P407 was prepared in a 15.4% solution with 2% iohexol. Antennas were placed percutaneously into extremely superficial liver, spleen, or kidney (target tissues) under US and CT guidance in 5 pigs under general anesthesia such that the expected ablation zones would extend into adjacent diaphragm, body wall, or bowel (non-target tissues). For experimental ablations, P407 was injected into the potential space between target and non-target tissues, and presence of a gel barrier was verified on CT. No barrier was used for controls. MW ablation was performed using a single antenna at 65W for 5 minutes. Gross dissection was performed after sacrifice to inspect tissues for thermal damage, which was verified using a histologic viability stain.

Antennas were placed 7 ± 3 mm from the organ surface for both control and gel-protected ablations (p<0.05). The volume of gel deployed was 49 ± 27 mL, resulting in a barrier with a thickness of 0.75 ± 0.48 cm. Ablations extended into non-target tissues in 12/14 control ablations with a mean non-target tissue burn of 3.8 cm2, but only 4/14 gel-protected ablations with a mean non-target tissue burn of 0.2 cm2 (p<0.05). The gel stayed at the injection site throughout power delivery, with interval resorption of gel and accumulation of contrast in the bladder by 2.5h post-procedure.

In this extreme scenario, P407 demonstrates viability as a tool for percutaneous tissue hydrodissection, as well as efficacy in protection of non-target structures during microwave ablation.

As a thermoreversible poloxamer being explored for many novel medical applications, P407 exhibits potential utility in percutaneous tissue hydrodissection, effectiveness in thermoprotection during microwave ablation, and ability for maintenance at the injection site for the duration of power application. Further comparison of P407 to existing hydrodissection fluids and continued investigations into pharmacologic properties appear warranted.

Moreland, A, Lubner, M, Ziemlewicz, T, Hinshaw, J, Kitchin, D, Johnson, A, Lee, F, Brace, C, Evaluation of an Experimental Thermoprotective Gel for Hydrodissection during Percutaneous Microwave Ablation: In Vivo Results.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14005481.html