Verifying If An Image Is Exposed Correctly - AGFA DR 18M User Manual

Verifying if an image is exposed correctly

On the NX workstation (type 21.00 or higher) an area of the DR
mammography image can be selected to measure the pixel value index (PVI).
As a result two values are displayed: the PVI Log value and the PVIc Log
value. The PVIc Log is the "offset corrected logarithmic pixel value index".
A reference value for the PVIc Log is provided to the user during installation.
1. Measure the PVIc Log of the image at the location of the AEC cells.
2. Compare the result to the reference value that is defined during
installation.
3. Estimate the amount of overexposure or underexposure on the acquired
image.
Table 2: Using the pixel value index (PVI) to estimate the exposure level
Measured PVIc Log value
compared to a reference value
12000 points higher
6000 points higher
2000 points higher
2000 points lower
6000 points lower
12000 points lower
DR 18M, DR 24M | Getting started | 57
Estimated exposure level
compared to a reference
exposure
400%
200%
125%
75%
50%
25%
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