Usefulness of Intraoperative Cone Beam CT Images on Video-assisted Thoracic Surgery.

For the resection of pulmonary ground glass opacity (GGO) or non-palpable nodule on video-assisted thoracic surgery (VATS), preoperative computed tomography (CT)-guided VATS marker pricking is usually performed. Recently, air embolisms after VATS marker pricking have been reported to be serious problems. The purpose of this study was to evaluate the usefulness of intraoperative cone beam CT images on VATS to avoid preoperative VATS marker pricking. The CT number of the both GGO and nodule indicate the range from -200 to -800 HU in general. We evaluated the detection ability of the lesion in seven elements and the simulated lungs. The result indicated that there was a linear equation of "y=1.0599×-2.1492" and the degree of correlation was "R(2)=0.9826" for the relationship between CT number and W number [voxel number in cone beam computed tomography (CBCT)]. Evaluation of low contrast resolution has been performed. The contrast noise ratios were 2.86 on CBCT and 1.50 on multi detector-row computed tomography (MDCT), while the relative contrast ratios were same both on CBCT and MDCT (0.19) as the lowest CT number (-700 HU). In clinical situation, four types of pulmonary lesions (pure GGO, mixed GGO, solid nodule, and cyst) were detected on MDCT, and intraoperative CBCT could identify all lesions as same configuration as on MDCT. The contrast noise ratio (CNR) and relative contrast ratio (RCR) could not admit the significant difference. In conclusion, the intraoperative CBCT can be used as a non-invasive image navigator for VATS, and the preoperative CT-guided VATS marker pricking can be avoided.