Elastographic measurements of in-vivo radiofrequency ablation lesions of the kidney

Background and Purpose: Elastography may prove useful for monitoring radiofrequency ablative (RFA) therapy because heat-ablated tissues are more elastic than untreated tissues. Herein, we report our initial evaluations of the reliability of elastography for delineating thermal-lesion boundaries at the time of RFA of porcine kidneys. Materials and Methods: In-vivo RFA was performed on 20 kidneys from 10 40-kg female pigs. Elastography was performed at the time of surgery and after 48 hours. The imaging plane was perpendicular to the axis of the RF electrode so that the ablated region was around the center of the plane. Measurements of the sections representing the same image plane used for elastography were taken at pathologic examination and compared with the measurements obtained from the elastograms. Results: We found a statistically significant correlation between elastography and pathology measurements with respect to the area and volume estimates (r = 0.9302 and r = 0.953, respectively). Overall, elastography slightly underestimated the lesion size, as judged by the digitalized pathologic images, a finding consistent with previous reports. Conclusion: We found a correlation between the area and volume estimates of thermal lesions that were based on elastographic images and the measurements from gross pathologic dimensions. A a significant limitation of renal RFA is the inaccuracy of current imaging modalities to provide real-time monitoring, and elastography may prove to be reliable for delineating the resulting thermal lesions.