NORMI 13 (T42023)
Operating Manual - Constancy Test
24
D703.131.00/03 en
Model calculation
The following pixel values were determined by the
ROI measurement of the reference step P
1
and
the adjoining steps P
0.65
and P
1.4
for 70 kV:
– P
1
or P
reference
: 13483
– P
dose+step
(P
0.65
): 16603
– P
dose+step
(P
1.4
): 10645
For the calculation of the limit values P
-1
and P
+1
,
these pixel values are entered in the appropriate
formula.
– Minimum deviation P
-1
:
13483 + 0.45 × (10645-13483) = 12206
– Maximum deviation P
+1
13483 + 0.45 × (16603-13483) = 14887
3.4.6 Spatial Resolution
The image of the X-ray test pattern should not be
of poorer quality compared with the initial state.
The measured values, in particular, should not
drop below the reference values determined in the
acceptance test. The limit value for spatial reso-
lution valid in the last acceptance test must not
be exceeded by any of the X-ray images obtained
with the test object.
3.4.7 Contrast Resolution
The number of discernible low contrast elements
in the test object shall not deviate from the ref-
erence value determined in the acceptance test.
The limit value for contrast resolution valid in the
last acceptance test shall not be exceeded.