5. Measurements with the Barracuda System
Fluoroscopy and Pulsed Fluoroscopy
2012-10/4.3A
131
Barracuda & QABrowser Reference Manual
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The next two pictures shows measurement on the same type of the system but instead
is the frame rate is 25 Hz. In this case a 15cc ionization chamber connected to an
EMM-Bias module was used instead.
Be aware that many ion chamber can be to "slow" to follow the dose rate waveform
accurately, since cable and chamber capacitance is higher and the signal output is
much less than that of a corresponding solid state detector, such as the R100.
Hints:
Pulsed fluoro screen is very handy to use for several applications and is not restricted
to only measure pulsed fluoro.
It has application when measuring in Cine mode with heavy filtered beam that make
the signal too low to use the Cine mode or when the dose rate is extremely low. Then
the noise level is too high to detect the pulses in the signal. Ion chambers with low
bandwidth can still be used in this mode, as well, even if the pulses cannot be detected
due to low bandwidth (e.g. Radcal flat 60cc Ion chamber). The pulsed fluoro mode
works also well on X-ray generators that only have a continuous fluoro output.
The Dose/pulse screen has been configured to always display the Dose rate and Pulse
dose rate continuously during the measurement period, even when pulse information is
lacking. Be aware of that during the fluoro the continuous dose rate value is displayed
but the dose rate value that is stored in the display after the measurement is based on
the total dose divided by the measured exposure time.
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