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Test-retest reproducibility of a deep learning–based automatic detection algorithm for the chest radiograph

Hyungjin Kim et al. — European Radiology (2020)


To perform test-retest reproducibility analyses for deep learning–based automatic detection algorithm (DLAD) using two stationary chest radiographs (CRs) with short-term intervals, to analyze influential factors on test-retest variations, and to investigate the robustness of DLAD to simulated post-processing and positional changes.


This retrospective study included patients with pulmonary nodules resected in 2017. Preoperative CRs without interval changes were used. Test-retest reproducibility was analyzed in terms of median differences of abnormality scores, intraclass correlation coefficients (ICC), and 95% limits of agreement (LoA). Factors associated with test-retest variation were investigated using univariable and multivariable analyses. Shifts in classification between the two CRs were analyzed using pre-determined cutoffs. Radiograph post-processing (blurring and sharpening) and positional changes (translations in x- and y-axes, rotation, and shearing) were simulated and agreement of abnormality scores between the original and simulated CRs was investigated.


Our study analyzed 169 patients (median age, 65 years; 91 men). The median difference of abnormality scores was 1–2% and ICC ranged from 0.83 to 0.90. The 95% LoA was approximately ± 30%. Test-retest variation was negatively associated with solid portion size (β, − 0.50; p = 0.008) and good nodule conspicuity (β, − 0.94; p < 0.001). A small fraction (15/169) showed discordant classifications when the high-specificity cutoff (46%) was applied to the model outputs (p = 0.04). DLAD was robust to the simulated positional change (ICC, 0.984, 0.996), but relatively less robust to post-processing (ICC, 0.872, 0.968).


DLAD was robust to the test-retest variation. However, inconspicuous nodules may cause fluctuations of the model output and subsequent misclassifications.

Key Points

• The deep learning–based automatic detection algorithm was robust to the test-retest variation of the chest radiographs in general.

• The test-retest variation was negatively associated with solid portion size and good nodule conspicuity.

• High-specificity cutoff (46%) resulted in discordant classifications of 8.9% (15/169; p = 0.04) between the test-retest radiographs.

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Hyungjin Kim, Chang Min Park & Jin Mo Goo

European Radiology (2020)

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