Intra-procedural evaluation of tumor coverage using 3D US images for percutaneous focal liver thermal ablation

Percutaneous thermal ablations are promising curative treatment techniques of focal liver tumors, particularly for those patients who are not eligible for surgical resection. Complete coverage of the targeted tumor by the thermal ablation zone and with a safety margin of 5-10 mm is required to ensure that complete tumor eradication will be achieved. 2D ultrasound (US) is a commonly used modality to guide this procedure; however, it has limitations in estimating the ablation tumor coverage due to the difficulty of evaluating tumor coverage using only one or multiple 2D US images. The use of intra-procedural 3D US is a promising approach to solve this unmet need. Although most of current approaches provide reformatted three orthogonal views to better evaluate the tumor coverage, comprehensive volumetric evaluation is rarely available. In this paper, for tumor-visible cases in US, we aim to investigate the ability of 3D US images to visualize the applicators and relevant surrounding structures, then assess the feasibility of evaluating the tumor coverage quantitatively using surface- and volume-based metrics. Using our previously developed 3D US liver ablation system, we collected 10 patients’ 3D US liver images in our clinical trial. The visibility of the applicator and relevant structures were assessed qualitatively. We then evaluated the surface error and volume accuracy of the tumor coverage. Results demonstrated that 3D US images allow visualization of the appropriate anatomical structures and applicators, and our volumetric evaluation can provide systematic knowledge of tumor coverage and an opportunity to correct the ablation applicator position intra-procedurally.