Contextualizing the Role of Volumetric Analysis in Pulmonary Nodule Assessment: AJR Expert Panel Narrative Review.

Abstract

Pulmonary nodules are managed based on their size and morphologic characteristics. Radiologists are familiar with assessing nodule size by diameter measured using manually deployed electronic calipers. Size may also be assessed by 3D volumetric measurements (referred to as volumetry) using software. Nodule size and growth are more accurately assessed by volumetry than by diameter, and the evidence supporting clinical use of volumetry has expanded, driven by its use in lung cancer screening (LCS) nodule management algorithms in Europe. The application of volumetry has the potential to reduce recommendations for imaging follow-up of indeterminate solid nodules without impacting cancer detection. Although changes in scanning conditions or volumetry software package may lead to variation in volumetry results, ongoing technical advances have improved the reliability of calculated volumes. Volumetry is now the primary method for determining size of solid nodules in the European LCS position statement and British Thoracic Society recommendations. In this article, we review technical aspects, advantages, and limitations of volumetry, and contextualize its use with respect to its importance relative to morphologic evaluation, role for predicting malignancy in risk models, and practical impact on nodule management, by considering specific scenarios. Implementation challenges and areas requiring further evidence are also highlighted.