Fluke Biomedical 35080M - Manual (Page 52)

Appendix
Mammographic Measurements With The Model 35080M
A
A-1
Section A
Mammographic Measurements with the Model 35080M
A.1 Introduction
We recommend that the two mammographic filter packs, K-edge Mammo Filter Pack (37355) and Linear
Mammo Filter Pack (37351) be used together. The K-edge Mammo Filter Pack (37355) is used first to
find a point between 27.5 kV and 29.5 kV very accurately. Then, the Linear Mammo Filter Pack (37351)
measurement is made at the same point to determine the necessary correction to apply to all readings
taken with the Linear Mammo Filter Pack (37351). The K-edge measurement should be performed each
time a generator is tested.
Part of the correction factor for the Linear Mammo Filter Pack (37351) is due to variations in tube filtration
and part is due to positional dependence. Therefore, if the Model 35080M non-invasive kVp Divider is
moved when using the Linear Mammo Filter Pack (37351), a new measurement at the K-edge
comparison kVp point must be made with the Linear Mammo Filter Pack (37351) to compute a new
correction factor.
The following procedure enables the first-time user to achieve good results. An experienced user can
take many short cuts. The kVp divider with the mammo kVp option is for use on molybdenum anode,
beryllium window tubes only.
A.2 K-Edge Measurement
MEASUREMENT SETUP
1. Remove the cone.
2. Remove the compression paddle, turn it upside down and reinstall as shown in Figure 4-3.
3. Place the Model 35080M kVp Divider (with a K-edge Mammo Filter Pack, 37355) on top of the
compression paddle as close as possible to the X-ray tube.
4. Level the kVp divider.
OSCILLOSCOPE SETUP
1. Connect the Model 35080M kVp Divider to the scope using a shielded cable.
2. Set the vertical sensitivity to 0.5 volts per division.
3. With the input in the ‘‘GROUND’’ position, adjust the vertical position control to place the trace on
the bottom graticule line.
4. Set the scope in single trace, storage mode.
5. Place the input selector switch in the ‘‘DC’’ position.
K-EDGE MEASUREMENT PROCEDURE
Part A
1. Set the X-ray generator for 25 kVp, 100 mA--or a mAs setting that provides the maximum tube
current--at least 50 mA.
2. Select the Mo (molybdenum) filter.
3. Make an exposure, adjusting the scope trigger level as necessary to get a stable trace.