Test purpose

Evaluation of the IQM signal calculation accuracy (segment-wise and cumulative) and the measurement reproducibility by utilizing a tolerance band defined for this test.

Test method

32 Head & Neck VMAT test fields (with 110 segments each) were calculated by the IQM CALC application, then delivered by a TrueBeam LINAC  for 15 fractions over a course of 50 days.

IQM segment based calculation accuracy was assessed by evaluating the
% pass rate for all delivered fields. The cumulative calculation accuracy was
measured by directly evaluating the deviation in measured cumulative signal from calculation.

IQM segment based signal reproducibility was evaluated by calculating the %STDEV for all measured signals across 15 fractions. The cumulative signal reproducibility was assessed by calculating overall deviation in measured cumulative signals from calculated signal.

Test results

A total of 52800 segments were delivered and measured.
The IQM segment-wise measured signal variation is mainly a function of signal size and accelerometer accuracy.  The mean %STDEV was calculated to be 4.60%. The cumulative measured signal was reproducible to within ± 1% throughout the measurement period.


IQM dynamic signal reproducibility per segment was within 5% of the mean value.