Characterization of the IQM System
Test purpose
Evaluate the stability and accuracy of each feature of the IQM.
Test method
The short-term and long-term signal reproducibility was evaluated. The signal linearity and dose rate dependency was tested. The inclinometer, barometer and thermometer measurements were compared against calibrated devices.
Test results
Simple photon beam measurements showed a short-term signal reproducibility with a standard deviation of 0.14% and a long-term (over 4 weeks) signal reproducibility with a standard deviation of 0.47%.
The linearity between the MU delivered and the changes in IQM signal is proportional: R2 = 1.
The dose rate dependency is minimal.
The IQM thermometer agreed to the calibrated thermometer to within 1.0
± 0.7°C.
The IQM barometer agreed to the mercury barometer to within 2.3 ± 0.4
mmHg.
The IQM inclinometer agreed with the spirit level for gantry: 0 and 180 degrees within 0.03 ± 0.01 degrees and for 90 and 270 degrees within 0.27 ± 0.03 degrees
For the collimator angle measurement, the IQM inclinometer agreed
with the plum-bob within 0.3 ± 0.2 degrees with the gantry at 90
degrees.
Conclusion
The IQM demonstrated:
- Valid temperature and pressure correction
- Useful gantry and collimator angle readings
- Valid and reproducible photon beam measurements
