Reproducibility, Linearity, & HVL Testing
CPI Canada Inc
Page 4 Rev. A X-Ray Generator Service Manual Supplement 740917-00
3.0 REPRODUCIBILITY
(Cont)
4.
Calculate and record the average dose mR.
5.
Calculate the difference mR - mR 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 mR.
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 (mR)
DIFFERENCE
DIFFERENCE
2
1
2
3
4
5
mR =
________
Calculate each of the differences
ie: DIFF
1
= mR
1
- mR.
Repeat for each remaining mR
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)
mR
Table 1: Reproducibility