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RaySafe Xi User Manual – Measurement definitions
For exposures longer than 4 seconds, the frame rate is continuously calculated as (number of pulses since last
update)/(time since last update). It may take another few seconds to get stable readings.
Frame rate is available for the R/F and mA/mAs detectors.
DOSE PER FRAME
The RaySafe Xi calculates Dose per Frame as (accumulated dose)/(number of pulses). If pulses can not be
counted, the Dose per Frame can not be calculated.
Dose per Frame is available for the R/F and mA/mAs detectors.
HVL (HALF VALUE LAYER)
The RaySafe Xi calculates HVL as a function of the signals from several sensor elements from the whole
exposure, if exposure time is less than 6 seconds.
If the exposure is longer than 6 seconds, a HVL value recorded approximately 2 seconds before end trig will be
displayed.
HVL is an indication of the beam quality and is defined as the amount of Al filtration, measured in mm, needed
to reduce the dose in half. HVL is kVp dependent. HVL should not be confused with total filtration.
HVL is available for R/F and mammography detectors.
TOTAL FILTRATION
Total filtration is a calculation of the amount of physical filtration between the X-ray source and the patient,
expressed in equivalent amount of mm Al.
The total filtration value measured may differ from the filtration stated by the X-ray manufacturer, as there might
be additional filtration not specified by the manufacturer.
mA AND mAs
The RaySafe Xi base unit with mAs is capable of measuring mA, mAs and time. If the peak mA is > 8 mA, it can
also measure pulses, frame rate and mAs per pulse.
When an exposure longer than 6 seconds has ended, a mA value recorded approximately 2 s before end trig is
displayed.
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