12 April 2002 Lesion conspicuity and AFROC performance in pulmonary nodule detection
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A test bank of verified chest radiographs was compiled for visual search experiments. The purpose was to investigate human performance in the detection of significant pulmonary nodules. Synthesized nodules supplemented native lesions. The distribution of all the lesions in the lung fields was consistent with the naturally occurring locations of these features. A measure of the physical characteristics of the lesions was derived in order to approximate the conspicuity of the synthetic to the natural nodules. The measure of conspicuity was given as (chi) =Tan(theta-1)S/N where (theta) is the maximum slope angle to the edge of the lesion profile, S is the mean pixel value of the lesion profile taken in four orientations, and N is the mean background pixel value taken in four orientations over one lesion dimension adjacent to the lesion. The variation in (chi) for each of the 81 lesions (46 natural and 35 synthetic) was plotted against SNR and edge angle. The influence of edge angle on the resulting (chi) values was more powerful than SNR for all the lesions in this experiment. Although there was an overall significant difference in (chi) values (p=0.015), observers were unable to distinguish synthetic from native lesions. Observer performance in nodule detection was measured by AFROC and supplemented with visual search recording. Correlation of AFROC scores and the (chi) values has shown no overall relationship (R2=0.0452) and this surprising result may be partly explained through inspection of the visual search recordings.
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David Manning, Susan C. Ethell, "Lesion conspicuity and AFROC performance in pulmonary nodule detection", Proc. SPIE 4686, Medical Imaging 2002: Image Perception, Observer Performance, and Technology Assessment, (12 April 2002); doi: 10.1117/12.462691; https://doi.org/10.1117/12.462691

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