Tomosynthesis produces three-dimensional images of an object, with non-isotropic resolution.
Tomosynthesis images are typically read by human observers in a stack viewing mode, displaying
planes through the tomosynthesis volume. The purpose of this study was to investigate whether
human performance in a signal-known exactly (SKE) detection task improves when the entire
tomosynthesis volume is available to the observer, compared to displaying a single plane through
the signal center. The goal of this study was to improve understanding of human performance
in order to aid development of observer models for tomosynthesis.
Human performance was measured using sequential 2-alternative forced choice experiments.
In each trial, the observer was first asked to select the signal-present ROI based on a single
2D tomosynthesis plane. Then, scrolling was enabled and the observer was able to select the
signal-present ROI, based on knowledge of the entire volume. The number of correct decisions
for 2D and 3D viewing was recorded, and the number of trials was recorded for which a score
increase or decrease occured between 2D and 3D readings.
Test images consisted of tomosynthesis reconstructions of simulated breast tissue, where
breast tissue was modeled as binarized power-law noise. Tomosynthesis reconstructions of designer
nodules of r = 250μm, r = 1mm, r = 4mm were added to the structured backgrounds.
For each signal size, observers scored 256 trials with signal amplitude set so that the proportion
of correct answers in the single slice was 90%.
For two observers, a slight increase in performance was found when adjacent tomosynthesis
slices were displayed, for the two larger signals. Statistical significance could not be established.
The number of decision changes was analyzed for each observer. For these two observers,
the number of decision changes that led to a score increase or decrease were outside the 95%
confidence interval of the decision change being random, indicating that for these two observers,
displaying the tomosynthesis stack did boost performance. For the other two observers, decision
changes that increased or decreased the score were within the 95% confidence interval of guessing,
indicating that the decision changes were due to a satisfaction of search effect.
However the results also indicate that the performance increase is small and the majority of
information appears to be contained in the tomosynthesis slice that corresponds to the center
of the lesions.