Test purpose

Quantify how sensitive the device is to beam delivery errors.

Test method

Various errors were introduced into a 10 cm x 10 cm beam as well as in a 1 cm x 1 cm beam. These errors included 1% change in MUs, 1 mm single leaf motion, 1 mm field size shift and energy changes.

Test results

Modifications to the photon beams resulted in changed IQM signal. The simulated errors were detected in 6 MV 10 cm × 10 cm photon beam. Twice the SD of the stability (1%) of the measurement was considered a “detected” error. For small fields (SBRT) the non-finite detector resolution changes the detectable errors. Simulated errors were detected in 6 MV 1 cm × 1 cm photon beam.


The IQM System demonstrates sufficient stability for online delivery quality assurance measurements and sufficient sensitivity for all simulated beam delivery errors.