5. Measurements with the Barracuda System
Mammography
Barracuda & QABrowser Reference Manual
2012-10/4.3A
142
Note 1-AN-52020-2 from RTI Electronics AB. Please also see section Angular
Sensitivity, MPD for details on sensitivity in different directions.
5.6.6.2 Normalization
A normalization function is available which enables all measurements to be virtually
performed at the same distance, increasing productivity. According to European
protocol (ECR 16263 EU, 1996), ESAK should be measured 45 mm above the breast
support. The QABrowser supports calculation of the dose at a user set virtual distance.
An example:
1. First readings from an exposure, where
the distance from the X-ray tube to the
breast support where the MPD is placed is
650 mm.
2. If the MPD is placed on the breast
support, the sensitive detector surface of
the MPD is situated 6.3 mm above the
breast support, which makes the distance
from the tube to the detector 643.7 mm.
ESAK is measured 45 mm above the
breast support and taking the detector
placement into consideration, the distance
from tube to the wanted measuring
position is then 605 mm.
3. When the normalizing function is used it
is indicated with a blue "N", as indicated in
the last figure. The dose and dose rate
values are then normalized to this virtual
position (at 605 mm SDD).
A practical consequence of usage of the normalizing function and scatter factor is that
the MPD can be kept at the same position on the breast support all the time when data
is collected for AGD.
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