Evaluation of a New Ultrasound Thoracoscope for Localization of Lung Nodules in Ex Vivo Human Lungs

Abstract

Background: Localization of small, nonvisible and nonpalpable nodules is challenging during video-assisted thoracoscopic surgery. We evaluated the feasibility of using a new ultrasound thoracoscope to localize nodules in resected ex vivo human lungs.

Methods: The tumor was localized and measured in its greatest dimension with a prototype ultrasound thoracoscope (XLTF-UC180; Olympus Corporation, Tokyo, Japan) at different frequencies (5.0 to 12.0 MHz) and different lung specimen states (deflated, semiinflated). Measured tumor size and depth from lung surface were compared and correlated to the true diameter and depth from lung surface acquired from pathologic morphology.

Results: Ex vivo evaluation was performed on 16 solid nodules and nine part solid ground-glass nodules. All tumors were successfully localized in the deflated lung specimens (average size, 13.7 ± 5.2 mm). The tumor boundaries were best evaluated with an ultrasound frequency of 10 MHz. Solid nodules were more easily visualized than ground-glass nodules. Part solid ground-glass nodules were not easily detected in the semiinflated specimen owing to peritumoral air surrounding the tumor. Tumor boundaries were also difficult to identify in deeply situated tumors and in lungs with underlying disease. A strong positive correlation existed between the ultrasound measurement and true measurement of tumor size (R² = 0.89, p < 0.001).

Conclusions: The ultrasound thoracoscope can be used to localize nodules in resected human lungs. The clarity of the tumor boundaries is influenced by the tumor type and depth and the underlying pulmonary disease. Complete lung deflation and the use of 10 MHz ultrasound frequency optimize the visualization of target tumors.