Contrast-Enhanced Ultrasonography Evaluation of Radiofrequency Ablation of the Prostate: A Canine Model

Abstract

Currently, there is no reliable method of monitoring the propagation of radiofrequency lesions in real time. We report our animal experience using contrast-enhanced ultrasonography (CEUS) to evaluate the lesion produced by radiofrequency ablation (RFA) in a canine model and investigate the feasibility to predict these lesions. Five male beagle dogs underwent RFA of the prostate. Radiofrequency was delivered under transrectal ultrasonography guidance. We created a lesion in the right and left lateral lobes of canine prostate. Post-RFA lesion size was measured with conventional ultrasonography and contrast-enhanced low-mechanical index perfusion imaging (ESAOTE DU8, CnTI) with a second-generation contrast agent (Sonovue). The prostates were assessed for a contrast void corresponding to the ablated tissue. All dogs were then immediately killed, and the prostates were harvested for pathologic analysis. The gross RFA lesions were measured to compare lesion size with that measured using CEUS. The RFA lesions could not be imaged accurately in real time with conventional grayscale or power Doppler sonography. With CEUS imaging, a clear lesion was identified at the site of each RFA application. As measured by CEUS, the lesions volume averaged 1.30 +/- 0.50 cm(3), compared with 1.32 +/- 0.53 cm(3) by measurement in the gross specimen (p = 0.324). CEUS appears to be an accurate modality for immediate monitoring of RFA procedure. Further study is necessary to assess the clinical utility of CEUS for monitoring RFA of localized prostate cancer.