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Aim: This study evaluates the assumption that global impression is created based on low spatial frequency components
of posterior-anterior chest radiographs. Background: Expert radiologists precisely and rapidly allocate visual attention
on pulmonary nodules chest radiographs. Moreover, the most frequent accurate decisions are produced in the shortest
viewing time, thus, the first hundred milliseconds of image perception seems be crucial for correct interpretation.
Medical image perception model assumes that during holistic analysis experts extract information based on low spatial
frequency (SF) components and creates a mental map of suspicious location for further inspection. The global
impression results in flagged regions for detailed inspection with foveal vision. Method: Nine chest experts and nine
non-chest radiologists viewed two sets of randomly ordered chest radiographs under 2 timing conditions: (1) 300ms; (2)
free search in unlimited time. The same radiographic cases of 25 normal and 25 abnormal digitalized chest films
constituted two image sets: low-pass filtered and unfiltered. Subjects were asked to detect nodules and rank confidence
level. MRMC ROC DBM analyses were conducted. Results: Experts had improved ROC AUC while high SF
components are displayed (p=0.03) or while low SF components were viewed under unlimited time (p=0.02) compared
with low SF 300mSec viewings. In contrast, non-chest radiologists showed no significant changes when high SF are
displayed under flash conditions compared with free search or while low SF components were viewed under unlimited
time compared with flash. Conclusion: The current medical image perception model accurately predicted performance
for non-chest radiologists, however chest experts appear to benefit from high SF features during the global impression.
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