Test purpose

The influence of the Integral Quality Monitor (IQM) transmission detector on the surface dose was evaluated using data from nine participating centers.

Test method

The change in surface dose with/without IQM was assessed for all available energies (4 standard, 2 FFF) and field sizes from 4 cm × 4 cm to 20 cm × 20 cm.

Test results

Pearson’s product–moment correlation coefficient ρ indicates a positive linear correlation between surface dose and the radiation field size for all studied flattened and unflattened beams, however, except for the 20 cm x 20 cm field size for the 10 MV FFF beam, the change in surface dose did not exceed 3.3%.


This study demonstrates clinically negligible changes in the surface dose for all investigated beams. A modest increase of surface dose when IQM is in the beam path can be considered acceptable and not a limiting factor for its clinical use.
Therefore, the time needed to implement the IQM system can be shortened since no additional commissioning beyond taking the beam attenuation into account (as a transmission factor or modified output factor) is needed regarding beam properties such as beam hardening and surface dose.