contrast-to-noise ratio
Image quality metric comparing signal difference between tissues to background noise. Critical parameter for cardiac imaging optimization.
Full Definition
Contrast-to-noise ratio (CNR) is a quantitative measure of image quality that compares the signal difference between two tissues or regions to the background noise level. In cardiac imaging, CNR is crucial for optimizing protocols in CT angiography, cardiac MRI, and nuclear imaging to ensure adequate differentiation between myocardium and blood pool, normal and abnormal tissue, or contrast-enhanced and non-enhanced regions. Higher CNR values indicate better image quality and diagnostic confidence. CNR is calculated as the absolute difference between mean signal intensities of two regions divided by the standard deviation of background noise.
Usage
Usage note: Distinguish from signal-to-noise ratio; specify tissues being compared when reporting CNR values.
In Context
- "The contrast-to-noise ratio between myocardium and blood pool was optimized by adjusting flip angle." — MRI protocol development
- "Poor contrast-to-noise ratio limited assessment of subendocardial enhancement." — Image quality assessment