Hepatic Microwave Ablation Zone Size: Correlation with Total Energy, Net Energy, and Manufacturer-Provided Chart Predictions.

Publication/Presentation Date

9-1-2016

Abstract

PURPOSE: To determine whether total energy (TE) reaching the microwave (MW) applicator or net energy (NE) exiting the applicator (after correcting for reflectivity) correlates better with hepatic MW ablation zone dimensions than manufacturer-provided chart predictions.

MATERIALS AND METHODS: Single-applicator, nonoverlapping ablations of 93 liver tumors (0.7-5.9 cm) were performed in 52 adult patients. TE and NE were recorded for each ablation. Long axis diameter (LAD), short axis diameter (SAD), and volume (V) of each ablation zone were measured on magnetic resonance imaging or computed tomography after the procedure and retrospectively compared with TE; NE; and manufacturer-provided chart predictions of LAD, SAD, and V using correlation and regression analyses.

RESULTS: For treated tumors, mean (± SD) TE and NE were 49.8 kJ (± 22.7) and 36.4 kJ (± 19.4). Mean LAD, SAD, and V were 5.8 cm (± 1.3), 3.7 cm (± 0.8), and 44.1 cm(3) (± 25.4). Correlation coefficients (95% confidence interval) with LAD, SAD, and V were 0.46 (0.28, 0.61), 0.52 (0.36, 0.66), and 0.52 (0.36, 0.66) for TE; 0.42 (0.24, 0.58), 0.55 (0.39, 0.68), and 0.53 (0.36, 0.66) for NE; and 0.51 (0.34, 0.65), 0.63 (0.49, 0.74), and 0.60 (0.45, 0.73) for chart predictions. Using regression analysis and controlling for TE, SAD was 0.34 cm larger in patients with cirrhosis than in patients without cirrhosis.

CONCLUSIONS: Correcting for reflectivity did not substantially improve correlation of energy values with MW ablation zone size parameters and did not outperform manufacturer-provided chart predictions. Correlations were moderate and variable using all methods. The results suggest a disproportionate influence of tissue factors on MW ablation results.

Volume

27

Issue

9

First Page

1389

Last Page

1396

ISSN

1535-7732

Disciplines

Diagnosis | Medicine and Health Sciences | Other Analytical, Diagnostic and Therapeutic Techniques and Equipment | Radiology

PubMedID

27425001

Department(s)

Department of Radiology and Diagnostic Medical Imaging

Document Type

Article

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