Test purpose

Investigation of the error sensitivity of the IQM signal.

Test method

Picket Fence type fields were used to evaluate the sensitivity of the IQM Detector for MLC leaf errors.
A single leaf offset was intentionally introduced during delivery of various Picket Fence fields with segment apertures of 3×1, 5×1, 10×1, and 24x1cm2 .
Both 2mm and 5mm decrease in a single MLC leaf width were used.

Test results

  • Statistical analysis indicates that the dosimetric differences detected by IQM were significant (p < 0.05) in all Picket Fence test deliveries.
  • The largest average IQM signal response of a 2 mm leaf error was found to be 2.1% and 5.1% by a 5mm leaf error for 3×1 cm2 field size.
  • The same error in 24×1 cm2 generates a 0.7% and 1.4% difference in the signal. See above table for detail.

These results were achieved completely automatically by the IQM system simply delivering a treatment plan designed as a picket fence test.


Small MLC leaf error can be detected. The sensitivity is more pronounced for smaller field sizes.

IQM could be beneficial for the verification of stereotactic treatments.