Effect of Hepatic Perfusion on Microwave Ablation Zones in an Ex Vivo Porcine Liver Model.
OBJECTIVE
To compare the size of ablation zones derived from nonperfused ex vivo livers with ablation zones created using an ex vivo perfused porcine liver model.


METHODS
Six fresh porcine livers were used to evaluate microwave ablation (MWA). Perfused (n = 3) and nonperfused (n = 3) livers were warmed to 37°C by oxygenated, O-positive human blood reconstituted with Ringer solution, using an organ perfusion circuit. During MWA, perfusion was discontinued in the nonperfused group and maintained in the perfused group. After MWA (140 watts × 2 min at 2.45 GHz) with the Acculis MTA System (AngioDynamics, Latham, New York), ablation zones were bisected sagittally. Sections were stained with nicotinamide adenine dinucleotide (NADH) and hematoxylin-eosin to assess viability of cells in ablation and marginal zones.


RESULTS
Comparison of 22 MWA zones (9 in perfused group, 13 in nonperfused group) was performed. Ablation zones demonstrated a central "white" and peripheral "red" zone. Cells in the white zone were nonviable with no NADH staining. The red zone showed progressive NADH staining toward the periphery, suggesting incomplete cell death. White and red zones of the perfused group were significantly smaller compared with the nonperfused group (short axis, 17.8 mm ± 2.7 vs 21.1 mm ± 3.2, P = .003; long axis, 40.69 mm ± 3.9 vs 39.63 mm ± 5.2, P = .44; intermediate zone,1.33 mm ± 0.04 vs 2.7 mm ± 0.14, P < .0001; mean ± SD).


CONCLUSIONS
MWA algorithms provided by this manufacturer are based on nonperfused organ data, which overestimate ablation zone size. Data from perfused liver models may be required for more accurate dosimetry guidelines.
Hepatopancreatobiliary and Liver Transplant Surgery Unit, University Department of Surgery, Royal Free London NHS Foundation Trust and University College London, London, United Kingdom. Electronic address: pulathis_ns@yahoo.co.uk.
Pulathis N
PN
Siriwardana
Interventional Oncology Service, University College Hospital, London, United Kingdom.
Saurabh
S
Singh
Interventional Oncology Service, University College Hospital, London, United Kingdom.
Edward W
EW
Johnston
Department of Cellular Pathology, Royal Free London NHS Foundation Trust, London, United Kingdom.
Jennifer
J
Watkins
Interventional Oncology Service, University College Hospital, London, United Kingdom.
Steve
S
Bandula
Interventional Oncology Service, University College Hospital, London, United Kingdom.
Rowland O
RO
Illing
Hepatopancreatobiliary and Liver Transplant Surgery Unit, University Department of Surgery, Royal Free London NHS Foundation Trust and University College London, London, United Kingdom.
Brian R
BR
Davidson
D055011:Ablation Techniques; D000818:Animals; D066298:In Vitro Techniques; D017078:Laser-Doppler Flowmetry; D008099:Liver / Q000098:blood supply* / Q000601:surgery*; D008833:Microcirculation; D008872:Microwaves / Q000627:therapeutic use*; D023421:Models, Animal; D010477:Perfusion; D013552:Swine