Time-related Changes in Computed Tomographic Appearance and Pathologic Findings after Radiofrequency Ablation of the Rabbit Lung: Preliminary Experimental Study

PURPOSE To evaluate correlations between computed tomographic (CT) appearance and pathologic findings after radiofrequency (RF) ablation of lungs and to determine whether CT appearance could predict the extent of the effective therapeutic area. MATERIALS AND METHODS The lungs of 14 rabbits were subjected to RF ablation and CT scans were obtained immediately and at various intervals thereafter. Four rabbits were killed immediately after the initial CT imaging ( n = 4). The remaining 10 rabbits were killed after additional CT scans at intervals of 3 days ( n = 2), 1 week ( n = 4), 2 weeks ( n = 2), and 3 weeks ( n = 2) after RF ablation. Pathologic findings were correlated with CT appearance. RESULTS Immediately after RF ablation, a restricted area of central dense opacity enclosed by an extensive area of ground-glass opacity was noted in the ablated region on CT images. Pathologically, the former corresponded to destructive tissue and the latter corresponded to tissue with some degree of injury. After 1 week, the entire ablated region appeared as a well-demarcated homogeneous dense opacity on CT that corresponded to necrotic tissue and its surrounding rim of granulation tissue on histopathologic examination, indicating that the enclosing extensive area of ground-glass opacity on the initial CT scan represented an ongoing necrosis. Within 2–3 weeks, the ablated region gradually contracted on the CT images, representing a tissue repairing process in which the granulation tissue was encroaching on the inner necrotic tissue. CONCLUSION Ground-glass opacity of the ablated region on CT immediately after RF ablation represents an ongoing necrosis.