5. Measurements with the Piranha System
Fluoroscopy and Pulsed Fluoroscopy
Piranha & QABrowser Reference Manual
2014-06/5.5C
104
Normally the external Dose Probe is used to
be able to measure the lowest possible dose
rate levels down to 0.1 µGy/s. Another reason
to use the external Dose Probe is that the
detector is much smaller than the Piranha
making it easier to position in front of the
image intensifier without affecting the
measuring field for the mA feedback loop.
If the image intensifier manually can control the mA and kV, then you can use the
Piranha for measurements down to about 0.7 µGy/s. For pulsed fluoroscopy even lower
levels can be measured.
As a secondary parameter the total dose is accumulated. After you have turned off the
fluoroscopy unit, this value is used to calculate the average dose rate as total dose
divided by the exposure time.
Note that for very low dose rate values the exposure time cannot be measured
accurately and the last dose rate value cannot be stored automatically in the display.
Then tap Hold to "freeze" the current value in the display. The waveform is also
acquired when you tap Hold. Waveform is also automatically acquired when the
selected delay time expires.
Select "I.I. input dose rate" as measuring parameter to be able to measure lowest
possible dose rate and tap Hold to "freeze" current value in the display. The total
accumulated dose is shoved after you have switched off the fluoroscopy unit.
5.4.1 Image Intensifier Input Dose Rate
Use patient equivalent phantom to measure the image intensifier input dose rate
according to manufacturer's specification:
1. Connect the Piranha Dose Probe to the Piranha.
2. Set up the Piranha and the handheld computer according to the description in Setting
Up the Piranha .
3. Select type of measurement.
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