CT-monitored Percutaneous Cryoablation in a Pig Liver Model: Pilot Study

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Abstract
To determine the safety and feasibility of percutaneous cryoablation with computed tomographic (CT) guidance in a pig liver model. Nine angiographic balloons (mean diameter, 9 mm) were placed in the livers of seven domestic pigs (mean weight, 30.0 kg +/- 14.0 [SD]) as tumor-mimicking lesions. By using ultrasonographic and CT guidance, two 2.4- or 3.0-mm cryoprobes were placed flanking the balloon, and a 15-20-minute freezing process was performed. Hemostasis was achieved by placing absorbable cellulose fabric down the probe tract. After 24-96 hours, animals were sacrificed, and their livers were removed and were sectioned axially at 5-mm intervals for comparison with CT images. All animals survived the procedure without complication. No serious hemorrhage was found in any case. Ice balls were readily visualized at CT because they appeared as areas of decreased attenuation (1.0 HU +/- 20.7) when compared with areas of normal liver (48.2 HU +/- 6.3, P < .05). The mean ablative margin was 1.7 cm, and only one of nine cases, the one with probe failure, had a positive margin. Beam-hardening artifact from the metal probes was present but did not interfere with the procedure. Ice-ball size and shape corresponded closely to the area of necrosis determined at histopathologic analysis. CT-monitored percutaneous cryoablation is feasible and safe in this pig liver model.