Analysis of variations in contrast‐detail experiments

Abstract

Three sources of variability in a contrast-detail (CD) experiment have been quantitated: within-observer variance, between-observer variance, and sample variance. It is concluded that (1) it is more efficient to increase the numbers of replicated images and observers than to increase the number of readings; (2) sampling and between-observer variations are approximately equal; (3) one can expect approximately 10% standard errors in the measured value of threshold detail or threshold contrast in a CD experiment which employs four observers, four replicate image samples, and one reading per observer.

Added copper filtration in digital paediatric double-contrast colon examinations: effects on radiation dose and image quality

“…As can be seen, there is a slight influence on contrast-detail resolution: every observer preferred the image exposed without Cu filter, although the variations between observers were quite large. This is in accordance with the findings of Cohen et al [21]. To analyse if the difference was statistically significant, the Mann-Whitney U-test was used and showed significant difference only for two object sizes, 0.5 mm (p = 0.01) and 0.7 mm (p = 0.03).…”

Image analysis methods for diffuse optical tomography

“…In tomography systems, the ability to resolve subtle contrast changes is typically most important, and a lower C-D threshold curve indicates the better system contrast resolution and therefore a higher level of imaging performance. 90 …”

“…88,89 This technique is used to quantify the combined performance of the imaging system and the image reader in detecting objects representing a clinically relevant range of sizes and contrasts within a domain, focusing on assessing the lower limits of each possible range. 90,91 A C-D graph of minimum detectable contrast level for all sizes of objects provides limiting data on two major regimes of system operation, namely 1. the spatial resolution for high contrast objects ͑high contrast, small object size͒, and 2. the lower level of contrast detectable for larger-sized objects. 81 Typical contrast-detail study test fields contain a series of objects representing a range of contrasts and diameters often in a regularly spaced pattern.…”

Dual-Energy Digital Mammography with a Full-Field aSi/CsI Flat-Panel Imager

“…35), it is necessary to compute the coefficients, k (j (Eqs. [27][28][29][30] and the SNR for low-and highenergy images, SNR S (Eq. 22).…”

“…[25][26][27][28][29][30][31][32][33][34][35] Contrast-detail curves of different digital chest systems have been independently studied without being compared to each other. Due to inter-reader variations are differences in study conditions (x-ray techniques, reading and scoring, etc.…”