Comparison of Conventional and Cone-Beam CT for Monitoring and Assessing Pulmonary Microwave Ablation in a Porcine Model

Purpose: To compare cone-beam computed tomography (CT) with conventional CT for assessing the growth and postprocedural appearance of pulmonary microwave ablation zones. Materials and Methods: A total of 17 microwave ablations were performed in porcine lung in vivo by applying 65 W for 5 minutes through a single 17-gauge antenna. Either CT (n = 8) or CBCT (n = 9) was used for guidance and ablation zone monitoring at 1-minute intervals. Postprocedural noncontrast images were acquired with both modalities. Three independent readers measured the length, width, cross-sectional area, and circularity of the ablation zones on gross tissue samples and CT and cone-beam CT images. The measurements were compared via linear mixed-effects models for postprocedural appearance and with a polynomial mixed effects model for ablation zone growth curves. Results: On postprocedural images, the differences between cone-beam CT and CT in mean length (3.84 vs 3.86 cm; Δ = −0.02; P =.70), width (2.61 vs 2.56 cm; Δ = 0.06; P =.46), area (7.84 vs 7.65 cm ² ; Δ = 0.19; P =.35), and circularity (0.85 vs 0.85; Δ = 0.01; P =.62) were not statistically significant after accounting for intersubject and interrater variability. Also, there was no significant difference between CT and cone-beam CT growth curves of the ablation zones during monitoring in terms of length (p _Int. = 1.00; p _Lin.Slope = 0.52; p _Quad.Slope = 0.69); width (p _Int. = 0.83; p _Lin.Slope = 0.98; p _Quad.Slope = 0.79), area (p _Int. = 0.47; p _Lin.Slope = 0.27; p _Quad.Slope = 0.57), or circularity (p _Int. = 0.54; p _Lin.Slope = 0.74; p _Quad.Slope = 0.80). Both CT and cone-beam CT overestimated gross pathologic observations of ablation length, width, and area (P <.001 for all). Conclusions: Cone-beam CT was similar to conventional CT when assessing the growth, final size, and shape of pulmonary microwave ablation zones and may be useful for monitoring and evaluating microwave ablations in the lung.