The Multi-Center Study “Feasibility of using IQM for QA tests of a medical linear accelerator” published in JACMP in January 2024 brought together Medical Physicists from some of the world’s leading Radiation Therapy Centers, including Princess Margaret Cancer Centre in Toronto, Mayo Clinic in Rochester, and Cedars Sinai Medical Center in Los Angeles to evaluate the use of IQM for Machine QA.
Since the IQM detector is easily mounted at the Linac collimator with high setup reproducibility, the research group investigated the IQM System’s sensitivity to Linac output variations at various gantry angles. The beam output for all energies were measured simultaneously with the IQM System and a reference Farmer type Chamber. at the cardinal gantry angles The results were compared with their reference reading at gantry zero position. After comparing the results, they concluded that the IQM system is able to detect any potential issues with changes in beam spectrum or other dosimetric or mechanical issues.
The upcoming IQM software release v1.10 embeds completely automated checks of beam output versus gantry angle into your daily clinical workflow. Pre-defined beam sequences for each beam energy with 20cm x 20cm fields at user definable gantry angles are stored in your Oncology Information System and delivered whenever needed.
When the predefined sequence is delivered, without any explicit user action, IQM fully automatically analyses the measured signal data and provides the resulting output constancy vs gantry angle in a comprehensive report.
The new IQM Linac Output (at different Gantry Angles) Report provides detailed information about the current QA result, showing the maximum deviation of today’s measurements and the output variations at each measured angle compared to the reference reading at gantry zero position.
The report also shows the long-term variations (for a user definable time period) in the linac output at each gantry angle and illustrates whether these variations are within the user-defined acceptance criteria.
The Integral Quality Monitor (IQM) system represents an innovative approach to integrate this usually tedious and time-consuming beam output vs. gantry angle check into the daily clinical workflow.
The unrivaled setup reproducibility of the IQM detector in combination with the fully automated data collection and analysis process provides highly reliable QA outcomes while saving valuable time for medical physicists and other staff involved in QA processes. By integrating QA processes seamlessly into the daily clinical workflow IQM allows medical physicists to allocate more time to other critical tasks, enhancing the overall productivity of the radiation therapy department and ensuring that daily beam output constancy checks are performed systematically.
The long-term tracking of linac performance data provides trend analysis and proactive maintenance. Long-term tracking with IQM helps in identifying gradual changes in the machine’s performance over time, serving as bases for equipment calibration, upgrades, and replacement.
In summary, the use of IQM for beam output versus gantry angle provides significant advantages in terms of accuracy, efficiency, and comprehensive monitoring of clinically relevant treatment scenarios. These benefits contribute to the delivery of high-quality, effective radiation therapy treatments.