Characterization of radiologists' search strategies for lung nodule detection: slice-based versus volumetric displays

Abstract

The goal of this study was to assess whether radiologists' search paths for lung nodule detection in chest computed tomography (CT) between different rendering and display schemes have reliable properties that can be exploited as an indicator of ergonomic efficiency for the purpose of comparing different display paradigms. Eight radiologists retrospectively viewed 30 lung cancer screening CT exams, containing a total of 91 nodules, in each of three display modes [i.e., slice-by-slice, orthogonal maximum intensity projection (MIP) and stereoscopic] for the purpose of detecting and classifying lung nodules. Radiologists' search patterns in the axial direction were recorded and analyzed along with the location, size, and shape for each detected feature, and the likelihood that the feature is an actual nodule. Nodule detection performance was analyzed by employing free-response receiver operating characteristic methods. Search paths were clearly different between slice-by-slice displays and volumetric displays but, aside from training and novelty effects, not between MIP and stereographic displays. Novelty and training effects were associated with the stereographic display mode, as evidenced by differences between the beginning and end of the study. The stereo display provided higher detection and classification performance with less interpretation time compared to other display modes tested in the study; however, the differences were not statistically significant. Our preliminary results indicate a potential role for the use of radiologists' search paths in evaluating the relative ergonomic efficiencies of different display paradigms, but systematic training and practice is necessary to eliminate training curve and novelty effects before search strategies can be meaningfully compared.

Fig 1

Navigation patterns from four radiologists in stereo mode. Each graph is the navigation recorded from one case interpretation. Two graphs in each row are taken from one radiologist’s interpretations in the beginning of the study (left) and the end of the study (right). The dark solid line represents viewing positions referenced to the scale on the left axis, and the gray solid line represents viewing thickness referenced to the scale on the right axis, with time.

Fig 2

Navigation patterns from four radiologists in orthogonal MIP mode. Each graph is the navigation recorded from one case interpretation. Two graphs in each row are taken from one radiologist’s interpretations in the beginning of the study (left) and the end of the study (right). The dark solid line represents viewing positions referenced to the scale on the left axis, and the gray solid line represents viewing thickness referenced to the scale on the right axis, with time.

Fig 3

Navigation patterns from four radiologists in slice-by-slice mode. Each graph is the navigation recorded from one case interpretation. Two graphs in each row are taken from one radiologist’s interpretations in the beginning of the study (left) and the end of the study (right). The dark solid line represents viewing positions with the time.

Fig 4

The diagrams a and b illustrate the missed nodules that received extra attention.