Siemens MAMMOMAT Inspiration - Relative Deviation Calculation; Linear Correlation and Offset

Prerequisites
MAMMOMAT Inspiration 13
SPB7-330.640.01.01.02
1.4 Relative deviation from corresponding average
Each sample x
n
from the set of measurements x
1
, x
2
, ..., x
N
possesses its own
relative deviation ∆x
rel, n
from the average x
av
according to the following definition:
n = 1, 2, ..., N
∆x
rel, N
= relative deviation for each value
Average value x
av
calculated according to Global average of values.
For maximum relative deviation select highest value of all calculated relative
deviations.
2 Linear correlation coefficient and offset
Calculate for quantity x = pixel value and quantity K= input air kerma value.
Assume that in total N (generally different) sample values K
1
, K
2
, ..., K
N
for the input
air kerma have been selected and the mean pixel values x
1
, x
2
, ..., x
N
in the
corresponding X-ray images have been recorded.
a) Calculate global average of all pixel values (x
av
) and global average of all input air
kerma values (K
av
)
b) Calculate average of pixel and input air kerma values (x
.
K)
av
and K
2
∆x
rel,n
x
n
x
av
–
x
av
------------------
=
xK⋅()
av
x
1
K
1
⋅ x
2
K
2
⋅ x
3
K
3
⋅ ... x
N
K
N
⋅++++
N
------------------------------------------------------------------------------------------------
=
K
2
()
av
K
1
2
K
2
2
K
3
2
... K
N
2
++++
N
---------------------------------------------------------
=