The context of the image quality parameter are explained in detail in the paper
.
Coming from the EPS values which is defined in ASTM E1025 and tested with E746 it leads to a formula for the visibility of details in dependence of the spatial resolution (SRb), the Contrast to Noise Ratio (CNR) and the perception threshold of the operator's eye (PT).
PT = dvisible * CNR
with dvisible is the visibility of a smallest just visible detail in the image.
with µeff as effective attenuation coefficient and "Delta w" as difference in wall thickness.
Hint: PT* is different from PT; it depends also slightly on the operator and the viewing conditions.
The main messages of the formula in a nutshell:
(a) With higher spatial resolution in the image smaller details are visible.
(b) With higher CNR (more contrast or less noise) smaller details are visible.
(c) Insufficient spatial resolution can be compensated by higher CNR. This leads to the .
|