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Reproducibility, Linearity, & HVL Testing
CPI Canada Inc
Use and disclosure is subject to the restrictions on the title page of this CPI document.
Page 4
Rev. C X-Ray Generator Service Manual Supplement 740917-00
3.0 REPRODUCIBILITY
(Cont)
4.
Calculate and record the average dose K (kerma) in mGy.
5.
Calculate the difference, K – K, for each exposure.
6.
Square each difference from the previous step.
7.
Calculate the sum of the differences squared.
8.
Calculate the standard deviation (S) by using the formula.
9.
Calculate reproducibility by dividing S by K.
10.
Table 5 shows example reproducibility calculations.
11.
If linearity is to be measured, it is suggested that dose measurements be taken at this time for
entry into tables 6 and 7. Refer to 4.0 LINEARITY for details.
IN TABLES 1 TO 4, 3 POINT MEANS THAT FOR GENERATORS WHERE KV, MA, AND TIME
SELECTION IS AVAILABLE, THE KV, MA AND MS VALUES SHOWN SHOULD BE USED. FOR
GENERATORS WHERE 2 POINT OPERATION ONLY IS AVAILABLE, THE KV AND MAS VALUES
SHOWN SHOULD BE USED.
3 point = Minimum kV, maximum mA, 100 ms.
2 point = Minimum kV, maximum mAs.
mAs = __________
EXP No.
DOSE (K)
mGy
DIFFERENCE DIFFERENCE
2
1
2
3
4
5
K =
________
Calculate each of the differences
ie: DIFF
1
= K
1
- K.
Repeat for each remaining K
value.
Square each difference. Then
calculate the sum of the difference
2
.
Sum of difference
2
= _________
Calculate standard deviation (S) using formula at beginning of this section: S = __________
Calculate reproducibility = S = _________ (not to exceed 0.045)
K
Table 1: Reproducibility