Fluke Biomedical TNT 12000 - Manual (Page 110)

TNT 12000
Users Manual
B-8
Table B-4. Specifications fo PTB Defined Attenudated Mammographic Beam Qualities
PTB Denomination kVp Added Filtration First HVL in mm AI
MH20 20 30 μ m Mo + 2.0 mm Al 0.45
MH24 25 30 μ m Mo + 2.0 mm Al 0.58
MH30 30 30 μ m Mo + 2.0 mm Al 0.67
MH35 35 30 μ m Mo + 2.0 mm Al 0.75
MH40 40 30 μ m Mo + 2.0 mm Al 0.83
MH50 50 30 μ m Mo + 2.0 mm Al 0.97
Typical energy 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. MV30 is chosen as the reference point for chambers receiving the
standard calibration while MH30 is chosen for chambers receiving the PTB calibration
option. Since the response of the chamber at MoMo28 is equivalent to the response at
MV30, the first curve is also considered normalized to MoMo28.
The typical correction factor curves for mammography are shown below normalized to
MV30 and MoMo28 in Figure B-6 and MH30 in Figure B-7.
Typical Correction Factors - Mammography
Normalized to MV30 and MoMo28
First HVL (mm A1)
Colrrection Factor
0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
1.05
1.04
1.03
1.02
1.01
1
0.99
0.98
0.97
0.96
0.95
fct40.eps
Figure B-6. 96035B Energy Correction Factor for Mammography Normalized to MV30 and MoMo28
Typical Correction Factors - Mammography
Normalized to MH30
First HVL (mm A1)
Colrrection Factor
0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
1.05
1.04
1.03
1.02
1.01
1
0.99
0.98
0.97
0.96
0.95
fct41.eps
Figure B-7. Energy Correction Factors for Model 96035B for Mammography Normalized to MH30