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5. Measurements with the Piranha System
Mammography
2014-06/5.5C
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Piranha & QABrowser Reference Manual
Mammography 5.5
This topic will describe how to measure kVp, dose, HVL, AGD (MGD), and time on a
mammography unit using the Piranha.
5.5.1 General
To measure kVp on a mammography unit is straightforward. This is true since the
Piranha automatically can detect whether the detector area is not fully uniformly
irradiated, by means of the
Position Check . The mammography kV calibrations available
for the Piranha is ranging from 18 to 49 kV. To confirm which range is used the digit 1 or
2 is displayed in square brackets on the bottom left corner of the QABrowser screen, as
shown below.
RQ (Radiation
Quality) Code
Range
Tube Voltage Range
for this RQ Radiation Quality
Selector
For new calibrations, only range 2 is being used. See the specifications section
Specifications, Piranha , for details about the different calibrations.
Please note that:
Mo/2 mm Al (M2)
Rh/1 mm Al (M5)
supports only kVp measurement, no dose measurement with Piranha is possible.
Mo/2 mm Al is not used that often but the GE DMR unit use Mo/1 mm Al so
simply add one extra 1 mm Al in the beam when measuring kVp. This since
the kV of the generator is the same regardless of the filtration.
You can either select the Tube Voltage as single parameter mode or All and get kVp
together with dose, dose rate, and time.
The displayed dose value has very little energy dependence because the dose value is
automatically compensated, using the tube voltage, which is measured simultaneously
for each exposure.
If any of the displayed values cannot be compensated or cannot be measured with full
accuracy, the symbol is displayed at the top of the screen. If the symbol is displayed
you can tap it to get more information.
You can also change the dose and dose rate units. Tap the dark part of the display
where the unit and its prefix are displayed to get the list of units. The value for the new
unit is automatically calculated and updated.
A delay of 5 ms is standard but can be changed. If you get a
High kVp message you
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