A 17-gauge triaxial microwave ablation system tuned for lung tissue yielded large circular zones of coagulation in vivo in porcine lungs. The coagulation zones created with bronchial occlusion and multiple antennas were significantly larger than those created with one antenna.

The purpose of this study was to compare a double freeze–thaw protocol to a triple freeze–thaw protocol for pulmonary cryoablation utilizing an in vivo porcine lung model. A total of 18 cryoablations were performed in normal porcine lung utilizing percutaneous technique with 9 each in a double- (10-5-10) and triple-freeze (3-3-7-7-5) protocol. Serial noncontrast CT images were obtained during the ablation. CT imaging findings and pathology were reviewed. No imaging changes were identified during the initial freeze cycle with either protocol. However, during the first thaw cycle, a region of ground glass opacity developed around the probe with both protocols. Because the initial freeze was shorter with the triple freeze–thaw protocol, the imaging findings were apparent sooner with this protocol (6 vs. 13 min). Also, despite a shorter total freeze time (15 vs. 20 min), the ablation zone identified with the triple freeze–thaw protocol was not significantly different from the double freeze–thaw protocol (mean diameter: 1.67 ± 0.41 cm vs. 1.66 ± 0.21 cm, P = 0.77; area: 2.1 ± 0.48 cm2 vs. 1.99 ± 0.62 cm2, P = 0.7; and circularity: 0.95 ± 0.04 vs. 0.96 ± 0.03, P = 0.62, respectively). This study suggests that there may be several advantages of a triple freeze–thaw protocol for pulmonary cryoablation, including earlier identification of the imaging findings associated with the ablation, the promise of a shorter procedure time or larger zones of ablation, and theoretically, more effective cytotoxicity related to the additional freeze–thaw cycle.

Purpose:To estimate the relative yield of therapeutic fl exible sigmoidoscopy compared with complete optical colonoscopy for isolated left-sided polyps ( Ն 6 mm in diameter) identifi ed at screening computed tomographic (CT) colonography. Materials and Methods:This retrospective institutional review board-approved and HIPAA-compliant study included a review of CT colonographic screening results in 6570 consecutive asymptomatic adults (3551 women, 3019 men; mean age, 56.8 years 6 7.3 [standard deviation]). Of 887 (13.5%) patients with cases positive for nondiminutive polyps ( Ն 6 mm), a subset of 171 patients met the inclusion criteria (a) of having left-sided-only lesions of 6 mm or larger identifi ed at CT colonography (rectum-to-splenic fl exure) and (b) of undergoing subsequent evaluation with complete optical colonoscopy. CT colonography-optical colonoscopy concordance and proximal-versus-distal diagnostic yield at optical colonoscopy were assessed. The 95% confi dence intervals (CIs) were calculated for relevant results. Results:From the study group of 171 patients, a total of 234 leftsided lesions of 6 mm or larger were prospectively reported at CT colonography, of which 222 (94.9%; 95% CI: 91.3%, 97.0%) were confi rmed as true-positive fi ndings at optical colonoscopy. With optical colonoscopy, an additional 17 benign left-sided polyps of 6 mm or larger (13 small, four large) were found in 11 patients, resulting in a total left-sided yield of 239 nondiminutive lesions, including 137 small polyps (6-9 mm) and 102 large lesions ( Ն 10 mm), 160 neoplasms, 82 advanced adenomas, and seven cancers. Evaluation of the colon proximal to the splenic fl exure in this cohort yielded eight small and two large benign polyps in nine patients but no proximal cancers or histologically advanced lesions. Conclusion:For patients with left-sided-only polyps detected at CT colonography, the additional yield of complete optical colonoscopy beyond the expected reach of fl exible sigmoidoscopy is very low and may not justify the added costs, potential risks, and procedural time.q RSNA, 2011