Lung nodule localization and size estimation on chest tomosynthesis

We aim to investigate the localization, visibility, and measurement of lung nodules in digital chest tomosynthesis (DTS).

Computed tomography (CT), maximum intensity projections (CT-MIP) (transaxial versus coronal orientation), and computer-aided detection (CAD) were used as location reference, and inter- and intra-observer agreement regarding lung nodule size was assessed. Five radiologists analyzed DTS and CT images from 24 participants with lung $\text{nodules}\ge 100{\mathrm{mm}}^3$ , focusing on lung nodule localization, visibility, and measurement on DTS. Visual grading was used to compare if coronal or transaxial CT-MIP better facilitated the localization of lung nodules in DTS.

The majority of the lung nodules (79%) were rated as visible in DTS, although less clearly in comparison with CT. Coronal CT-MIP was the preferred orientation in the task of locating nodules on DTS. On DTS, area-based lung nodule size estimates resulted in significantly less measurement variability when compared with nodule size estimated based on mean diameter (mD) ( $p<0.05$ ). Also, on DTS, area-based lung nodule size estimates were more accurate ( $\mathrm{SEE}=38.7{\mathrm{mm}}^3$ ) than lung nodule size estimates based on mean diameter ( $\mathrm{SEE}=42.7{\mathrm{mm}}^3$ ).

Coronal CT-MIP images are superior to transaxial CT-MIP images in facilitating lung nodule localization in DTS. Most $\text{nodules}\ge 100{\mathrm{mm}}^3$ found on CT can be visualized, correctly localized, and measured in DTS, and area-based measurement may be the key to more precise and less variable nodule measurements on DTS.