Test 4: Detector Linearity
MAMMOMAT Inspiration 29
SPB7-330.640.01.01.02
Figure 5 ROI Positioning
10. Note mean pixel value and standard deviation (SD) inside ROI.
11. Repeat steps 7 to 10 for all tube load values in Test form Test 4.
12. Calculate the linear correlation coefficient between input air kerma and resulting
mean pixel value (see Linear correlation coefficient and offset, page 13).
13. Calculate detector offset for mean pixel value versus input air kerma (see Linear
correlation coefficient and offset, page 13).
14. For each of the images generated in steps 7 to 11 calculate the SNR in the
corresponding evaluation ROIs by taking into account the result for the detector
offset from previous step (step 13); note SNR into corresponding column in Test
form Test 4.
15. Repeat steps 7 to 14 for target/filter combinations Mo/Rh and W/Rh. Note
corresponding results in Test form Test 4.
16. Close examination.
Performance Criteria and Corrective Action
The linear correlation coefficient should be greater than 0.99.
The Offset should be between 45 and 55.
The SNR should exceed indicated lower thresholds.
2 cm
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