Fluke Biomedical 35080M - Manual (Page 30)

Linear Mammo Filter Pack Option (37351)
Introduction
5
5-1
Section 5
Linear Mammo Filter Pack Option (37351)
5.1 Introduction
The Linear Mammo Filter Pack (37351) provides a non-invasive way to make kVp measurements of
mammographic X-ray generators. This filter pack features nearly perfect linearity for precision
measurements between 22 and 40 kVp (for beryllium window, molybdenum anode mammographic
generators with molybdenum filtration).
5.2 Specifications
Intended Use
Beryllium window, molybdenum anode mammographic generators
Range
22.0 kVp to 40.0 kVp
Accuracy
± 1.0 kV exclusive of filtration effects
Sensitivity
0.01 volt per kV
Cal
0.200 V (20.0 kV)
Minimum Anode Current
50 mA
Target to kVp Divider Distance
12 in to 24 in (30.5 to 61 cm)
5.3 Theory of Operation
The Linear Mammo Filter Pack (37351) is similar in construction to the Wide Range linear diagnostic filter
pack except that the filter elements are much thinner. As expected in mammography, measurements are
more sensitive to variations in added filtration than in the diagnostic range. Thus, the Linear Mammo
Filter Pack (37351) is normally used in conjunction with the K-edge Mammo Filter Pack (37355). 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 the Linear Mammo Filter Pack (37351) readings.
The reading from the Linear Mammo Filter Pack (37351) is compared to that taken with the Cadmium K-
edge Mammo Filter Pack (37355) and a kV correction value for the Linear Mammo Filter Pack (37351) is
computed. This correction value is applied uniformly to all readings taken with the Linear. 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 when using the Linear Mammo Filter Pack (37351), if the Model 35080M kVp
Divider is moved, a new measurement at the K-edge comparison kVp point must be made with the Linear
Mammo Filter Pack (37351) and a new correction factor computed.