Different pixel pitch and maximum luminance of medical grade displays may result in different evaluations of digital radiography images

Abstract

Aim

To evaluate the effects of display pixel pitch and maximum luminance on intra- and inter-observer reproducibility and observer performance when evaluating chest lesions and bone fractures.

Materials and methods

This was a multi-institutional study for a retrospective interpretation of selected digital radiography images. Overall, 82 images were selected by senior radiologists, including 50 cases of chest lesions and 32 cases of bone fractures. These images were displayed at two pixel pitches (0.212 and 0.165 mm size pixels) and two maximum luminance values (250 and 500 cd/m²) and reviewed twice by senior and junior radiologists. All the observers had to indicate the likelihood of the presence of the lesions and to rate the relative confidence of their assessment. Cohen Kappa statistic was computed to estimate the reproducibility in correctly identifying lesions; for multi-reader-multi-case (MRMC) analysis, weighted Jackknife Alternative Free-response Receiver Operating Characteristic (wJAFROC) statistical tools was applied.

Results

The intra-radiologist and inter-observer reproducibility values were the highest for the 0.165 mm size pixel at 500 cd/m² display, for both chest lesions and bone fractures evaluations. As regards chest lesions, observer performances were significantly greater with 0.165 mm size pixel display at 500 cd/m² than with lower maximum luminance and/or larger pixel pitch displays. Concerning bone fractures, the performance obtained with 0.212 mm size pixel display at 250 cd/m² was statistically lower than that obtained with 0.165 mm sixe pixel display at 500 cd/m².

Conclusion

Our results indicate that an increased maximum luminance level and a decreased pixel pitch of medical-grade display improve the accuracy of detecting both chest lesions and bone fractures.

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