Ablation of renal tumors in a rabbit model with interstitial saline-augmented radiofrequency energy: Preliminary report of a new technology

Objectives. To evaluate the efficacy of interstitial saline radiofrequency energy for reproducibly ablating nonmalignant (control) and malignant (the VX-2 tumor) renal tissue in a rabbit model, and to determine the ability of conventional gray-scale and power sonography to image the tumor and ablati ve process in real time before, during, and after treatment. Methods. The VX-2 tumor was implanted beneath the renal capsule in 18 rabbi t kidneys. Twelve days after implantation, 50 W of 500-kHz radiofrequency e nergy was delivered into the surgically externalized renal tumor and contra lateral control kidney for 30 or 45-second treatment intervals using an int erstitial saline-augmented radiofrequency probe (the virtual electrode). Lo calization of the tumor and response to treatment were imaged with gray-sca le and power Doppler ultrasonography. The effect of radiofrequency and exte nt of the destructive process on benign and malignant renal tissue were eva luated histologically. Results. Mean tumor size was 1.3 x 0.7 cm. Both 30 and 45-second treatment intervals provided marked tissue/tumor ablation. Cross anatomic and histolo gic analysis showed time-dependent ablated lesions averaging 1.4 +/- 0.3 x 1.0 +/- 0.3 cm (30-second treatment) and 1.8 +/- 0.4 x 1.5 +/- 0.3 cm (45-s econd treatment), with clear demarcation of the surrounding parenchyma. Con ventional gray-scale sonography allowed visualization of the ablative proce ss, and power Doppler ultrasound demonstrated changes in the vascular patte rn of the tumor both before and after ablation. No immediate treatment-rela ted complications were observed. Conclusions. These preliminary studies in a rabbit model demonstrate the fe asibility of using the interstitial saline-augmented electrode to ablate sm all renal tumors and the ability to simultaneously visualize the ablative p rocess using real-time ultrasonography. This technology may have the potent ial to treat small renal tumors in a minimally invasive manner in the clini cal setting. (C) 1999, Elsevier Science Inc. All rights reserved.