Lung cryoablation: morphological evolution and CT patterns of the ablation zone.

Abstract

Background: The morphological evolution of lung ablation zones following cryoablation (CA) remains incompletely characterized. This study aimed to describe CT pattern evolution up to 18 months and evaluate the 1-month pattern as an early marker of long-term morphological trajectory.

Methods: This retrospective single-center study included 58 lesions in 28 patients treated with CT-guided CA (triple-freeze protocol, 2020-2024). Non-contrast CT was performed at 1, 3, 6, 12, and 18 months. Ablation zones were classified into five patterns: cavity, nodular, fibrosis, atelectasis, and reversed halo sign (RHS). Univariate analyses explored factors associated with each pattern at 1 and 6 months.

Results: At 1 month, cavity predominated (47%), followed by nodular (31%), fibrosis (10%), atelectasis (7%), and RHS (5%). By 6 months, fibrosis became the predominant pattern (43%); by 18 months (n = 34), it reached 65% and cavity disappeared. Median major axis decreased from 29 [22-34] mm to 17 [0-23] mm at 6 months (p < 0.001). Atelectasis at 1 month were associated with persistent atelectasis at 6 months (100%, 7/7 vs. 12/51, 24%; p < 0.001) and pleural contact (p = 0.016). The nodular pattern showed a non-significant trend toward fibrotic resolution (61% vs. 35%, p = 0.087). No procedural variable was associated with CT pattern.

Conclusion: The 1-month CT pattern may serve as an imaging marker of long-term ablation zone evolution. Atelectasis and RHS were associated with atelectasis, whereas fibrosis became the predominant pattern and cavity disappeared over time. These exploratory findings require prospective validation in larger cohorts.