Fluke Biomedical TNT 12000 - Manual (Page 108)

TNT 12000
Users Manual
B-6
Typical Correction Factors - Diagnostic Unattenuated Beam
Normalized to DV70
First HVL (mm A1)
Colrrection Factor
1 1.5 2 2.5 3 3.5 4 4.5 5 5.5
1.08
1.06
1.04
1.02
1
0.98
0.96
0.94
0.92
40
30
50
70
120 150
90
100
fct36.eps
Figure B-4. Energy Correction Factors for Model 96035C in Unattenuated Beam Normalized to DV70
All 96035B ion chambers must have an actual correction factor within ± 1.5 % of the
value shown in the curves at any point.
The numerical value shown beside each point is the kVp value of that point in the DV
series of beam qualities. Users making measurements in an unattenuated beam may use
these values to easily obtain the appropriate correction factor. For a more precise
correction factor value, the user may calculate the actual first HVL and locate the proper
correction value on the curve.
Diagnostic – Attenuated Beam (Behind the Phantom)
The energy correction factors for the 96035B in the attenuated diagnostic beam are
determined using the PTB defined DN series of beam qualities given below in Table B-2.
Table B-2. Specifications for PTB Defined Attenuated Beam Qualities
PTB
Denomination
kVp
Added Filtration
in mm AI
First HVL in mm
AI
First HVL in mm
Cu
DN40 40 6.5 2.2 0.07
DN50 50 12.5 3.4 0.123
DN60 60 18.5 5.0 0.207
DN70 70 23.5 6.2 0.289
DN80 80 29.5 7.8 0.403
DN90 90 32.5 9.0 0.501
DN100 100 36.5 10.1 0.609
DN120 120 42.5 12.0 0.839
DN150 150 52.5 14.1 1.245
Typical correction factor curves are obtained by dividing the calibration factor at each
beam quality by the calibration factor at a reference point and plotting the result versus
first HVL.
The typical correction factor curve for the attenuated beam is normalized to DH70 in