Study design. Asterisk denotes that each subset was obtained with a different scan protocol (Table I). Dagger denotes that each ten images from a subset were compressed to each compression ratio. CR: Compression ratio. CT: Computed tomography. HDR-VDP: High-dynamic range visual difference predictor. JPEG: Joint Photographic Experts Group. PSNR: Peak signal-to-noise ratio. ROC: Receiver operating characteristic.
The readers’ responses determined at each compression ratio. Each bar represents the different readers. The height of each bar indicates the number of distinguishable image pairs. Each gray shade represents each subset (white, subset A; light gray, subset B; middle gray, subset C; dark gray, subset D; black, subset E).
The correlation between the number of readers with positive response (rating a compressed image as distinguishable from its original) and each of the three indices. The symbols ◻, ○, △, , and × represent the subsets A, B, C, D, and E, respectively. The graphs show the results for the three indices: (a) The compression ratio , (b) the PSNR , and (c) the HDR-VDP .
Scatter plots of the three indices for the five subsets. The symbols ○ and × represent negative (indistinguishable image pairs) and positive responses (distinguishable), respectively. The dashed horizontal lines represent cutoff values yielding the highest accuracy in receiver-operating-characteristic analyses. The graphs show the results for the three indices: (a) the compression ratio, (b) the PSNR, and (c) the HDR-VDP.
Scan parameters and patient demographics for each subset.
Pooled responses of the five radiologists. Note: Data are the number of distinguishable image pairs. A value (adjusted by the use of the Bonferroni correction) indicates a significant difference among the five subsets. An en dash (–) indicates that a value could not be calculated.
Results of the correlation and ROC analyses. Note: Data in parentheses are the 95% confidence intervals. AUC: Area under the curve. CR: Compression ratio. HDR-VDP: High-dynamic range visual difference predictor. PSNR: Peak signal-to-noise ratio. ROC: Receiver operating characteristic.
Article metrics loading...
Full text loading...