Interactions of lesion detectability and size across single-slice DBT and 3D DBT

Abstract

Three dimensional image modalities introduce a new paradigm for visual search requiring visual exploration of a larger search space than 2D imaging modalities. The large number of slices in the 3D volumes and the limited reading times make it difficult for radiologists to explore thoroughly by fixating with their high resolution fovea on all regions of each slice. Thus, for 3D images, observers must rely much more on their visual periphery (points away from fixation) to process image information. We previously found a dissociation in signal detectability between 2D and 3D search tasks for small signals in synthetic textures evaluated with non-radiologist trained observers. Here, we extend our evaluation to more clinically realistic backgrounds and radiologist observers. We studied the detectability of simulated microcalcifications (MCALC) and masses (MASS) in Digital Breast Tomosynthesis (DBT) utilizing virtual breast phantoms. We compared the lesion detectability of 8 radiologists during free search in 3D DBT and a 2D single-slice DBT (center slice of the 3D DBT). Our results show that the detectability of the microcalcification degrades significantly in 3D DBT with respect to the 2D single-slice DBT. On the other hand, the detectability for masses does not show this behavior and its detectability is not significantly different. The large deterioration of the 3D detectability of microcalcifications relative to masses may be related to the peripheral processing given the high number of cases in which the microcalcification was missed and the high number of search errors. Together, the results extend previous findings with synthetic textures and highlight how search in 3D images is distinct from 2D search as a consequence of the interaction between search strategies and the visibility of signals in the visual periphery.

Comparative observer effects in 2D and 3D localization tasks

“…This finding would appear to be at odds with recent studies by Lago, Eckstein, and colleagues, 33 , 58 – 60 demonstrating substantial performance reductions for small targets in 3D search tasks. However, it is important to note a fundamental difference between those experiments and the results reported here.…”

“…In fact, validation of classification-image estimation for localization tasks is based on generating responses from a scanning linear model and showing that the classification image accurately estimates the kernel of this model. This class of model has been used to understand search in medical images previously, [62][63][64][65] although the recent results of Lago et al 59,60 serve as a caution when peripheral vision effects may be present. Nonetheless, the classification images can be used to understand how much of the subject's efficiency is due to the spatial weighting implemented in the scanning kernel and how much is due to other processes in the localization tasks (e.g., inefficient search or internal noise).…”

Measurement of the useful field of view for single slices of different imaging modalities and targets

“…12,29 The visibility of the targets in the visual periphery is critical to guide the eye movements toward likely target locations. 19,20,[29][30][31] Previous studies have shown that overall detection performance improves for simulated masses in 3-D volumes 14 as well as real masses in DBT images. 32 Thus, it is likely that the foveal and peripheral performance would increase during active multiple slice scrolling and UFOV measurements would increase for multiple slice DBT images.…”

“…8,9 This value has been estimated to be a ∼2.5deg radius circle by many studies using chest radiographs and has been extensively adopted by many authors. 7,[10][11][12][13][14][15][16] However, the UFOV size is related to the complexity of the task and image modality. 5,6,10 Some studies found that the UFOV estimate of 2.5-deg radius might be too large to be considered as an unequivocal standard.…”

“…4,17,23,24 With the increase in the volume of image data with newer 3-D and pseudo-3-D imaging modalities, including computed tomography (CT) and digital breast tomosynthesis (DBT), radiologists must rely more heavily in visual processing away from the point of gaze to guide their eye movements toward a region of interest. 10,13,14,25 Thus, there is renewed interest in studying the ability of observers to detect abnormalities in the visual periphery.…”