Microwave ablation with loop antenna: in vivo porcine liver model.
OBJECTIVE
To determine the effectiveness of tissue ablation with a loop microwave antenna in various configurations in porcine liver tissue.


METHODS
Microwave energy was applied for 7 minutes at 60 W in six porcine livers (mean weight, 68.2 kg) by using single (n = 7) or dual 2.7-cm loop microwave probes in parallel (n = 9) or orthogonal (n = 9) configurations. Volume, diameter, shape, and temperature of the zone of necrosis and the presence of viable tissue inside the loop were determined and compared by means of factorial analysis of variance.


RESULTS
Mean lesion volume and maximum diameter, respectively, were 32.2 cm(3) +/- 14.4 (SD) and 4.6 cm +/- 1.4 for lesions ablated with parallel probes (parallel lesions), 29.5 cm(3) +/- 8.1 and 4.3 cm +/- 0.6 for lesions ablated with orthogonal probes (orthogonal lesions), and 6.4 cm(3) +/- 1.9 and 3.4 cm +/- 0.62 for lesions ablated with single probes (single lesions) (P <.05, single vs parallel and orthogonal lesions). Mean minimum diameter was greatest for orthogonal lesions (3.5 cm +/- 0.53; P =.017, parallel vs orthogonal lesions). Orthogonal lesions had the highest mean internal temperature (97.2 degrees C) versus parallel (91.9 degrees C) and single (60.0 degrees C) lesions. All orthogonal lesions heated to 60 degrees C in comparison to eight of nine parallel and four of seven single lesions. The mean time to reach 60 degrees C was shortest for orthogonal lesions (93.3 seconds) versus parallel (123.8 seconds) and single (263.0 seconds) lesions. Orthogonal lesions were the most spherical. Viable tissue was present in the center of five of seven single, six of nine parallel, and zero of nine orthogonal lesions.


CONCLUSIONS
Loop microwave antennas allow precise control and effective ablation of targeted tissue, particularly in the orthogonal configuration.
Department of Radiology, University of Wisconsin Hospitals and Clinics, E3/311 Clinical Science Center, 600 Highland Ave, Madison, WI 53792, USA.
Sarah A
SA
Shock
Kenneth
K
Meredith
Thomas F
TF
Warner
Lisa A
LA
Sampson
Andrew S
AS
Wright
Thomas C
TC
Winter
David M
DM
Mahvi
Jason P
JP
Fine
Fred T
FT
Lee
D000818:Animals; D017115:Catheter Ablation; D004195:Disease Models, Animal; D005260:Female; D006979:Hyperthermia, Induced; D008099:Liver / Q000000981:diagnostic imaging / Q000473:pathology* / Q000601:surgery*; D008279:Magnetic Resonance Imaging; D008872:Microwaves; D009336:Necrosis; D011859:Radiography; D013552:Swine