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Published online before print February 16, 2006, 10.1148/radiol.2383050262
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Microwave Ablation: Results with a 2.45-GHz Applicator in ex Vivo Bovine and in Vivo Porcine Liver1

Andrew U. Hines-Peralta, MD, Nadeer Pirani, MD, Peter Clegg, PhD, Nigel Cronin, PhD, Thomas P. Ryan, PhD, Zhenjun Liu, MD and S. Nahum Goldberg, MD

1 From the Department of Radiology, Beth Israel Deaconess Medical Center, Harvard Medical School, 1 Deaconess Rd, WCC 308B, Boston, MA 02215 (A.U.H., N.P., Z.L., S.N.G.); Department of Physics, University of Bath, Bath, England (P.C., N.C.); and Microsulis Americas, Waltham, Mass (P.C., N.C., T.P.R.). From the 2004 RSNA Annual Meeting. Received February 15, 2005; revision requested April 12; revision received June 2; accepted June 21; final version accepted September 1. Supported by Microsulis. Address correspondence to S.N.G. (e-mail: sgolber{at}caregroup.harvard.edu).


Figure 1
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  		Figure 1: A 2.45-GHz microwave applicator. A ceramic microwave antenna is embedded within the 5.7-mm-diameter shaft (arrow). Energy is applied to the tissue via the applicator at 2.45 GHz.

 

Figure 2
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  		Figure 2a: Graphs show short-axis coagulation diameters for microwave ablation of (a) ex vivo and (b) in vivo liver. For ex vivo coagulation, longer treatment durations result in continuing gains in short-axis diameter. In contrast, in vivo coagulation reaches a relative plateau by 8 minutes, with no substantial further increase in coagulation observed after longer treatment applications.

 

Figure 2
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  		Figure 2b: Graphs show short-axis coagulation diameters for microwave ablation of (a) ex vivo and (b) in vivo liver. For ex vivo coagulation, longer treatment durations result in continuing gains in short-axis diameter. In contrast, in vivo coagulation reaches a relative plateau by 8 minutes, with no substantial further increase in coagulation observed after longer treatment applications.

 

Figure 3
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  		Figure 3: Three-dimensional contour plots. Left: Three-dimensional map for ex vivo findings shows relationship between treatment duration (x-axis), applied power (y-axis), and short-axis coagulation diameter (z-axis). Note that coagulation diameter continues to increase even after 8 minutes. Right: For the in vivo short-axis coagulation diameter, the greatest increase in coagulation occurs within 8 minutes, with a relative plateau for longer treatment durations.

 

Figure 4
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  		Figure 4: Graph compares ex vivo and in vivo coagulation diameters at selected applied power settings. At 150 W and 100 W (not shown), in vivo diameters were larger than ex vivo diameters for treatment durations of 8 minutes or less. However, for durations longer than 8 minutes, ex vivo diameters were larger than in vivo diameters. At 50 W, ex vivo diameters are greater than in vivo diameters, a finding typical of ablation devices.

 

Figure 5
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  		Figure 5: Gross pathologic appearance of microwave ablation. Ablated tissue is shown sectioned perpendicular to the applicator axis. At 150 W after 8 minutes of treatment, the in vivo (left) "white zone" coagulation diameter is 5.7 cm ± 0.2 (arrows), significantly larger than the corresponding ex vivo (right) diameter of 4.9 cm ± 0.2 (arrows).

 




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