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Novel Approach to Patient Specific QA for VMAT Treatment Plans Using RadCalc Image Analysis Tool in Conjunction with Machine Trajectory Files

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F O'Grady

F O'Grady1*, C Fitzherbert2 , F Zhou2 , C Hand2 , (1) University of Pennsylvania, Philadelphia, PA, (2) Albert Einstein Medical Center, Philadelphia, PA


SU-I-GPD-T-300 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: To assess the utility of the RadCalc Image Analysis Tool in patient specific QA for volumetric modulated arc therapy (VMAT) treatment plans as an alternative to the conventional approach which relies on detector measurements. To show that robust QA can be achieved by combining a dose comparison to check the treatment planning system (TPS) and an intensity map comparison using information in the machine trajectory log file to check data transfer and machine delivery.

Methods: Planar dose maps exported from the TPS and intensity maps generated from the trajectory log files were compared to dose and intensity maps generated from the treatment plan with the RadCalc Image Analysis Tool for 26 VMAT fields from Eclipse. All data was analyzed using a gamma index of 3%/3mm with a passing criteria of 90%. Pass rates were recorded for each field and for both QA methods. To further test the method, 10 fields were modified in RadCalc by manipulating control points and re-analyzed for dose and intensity map comparisons.

Results: With the conventional QA approach 100% of the plans passed. With this novel approach 100% passed the dose map comparison and 96.2% (25/26) passed the intensity map comparison. However, the one failing field passed at a gamma index of 3%/4mm. All modified fields failed for both criteria.

Conclusion: Using the RadCalc Image Analysis Tool in conjunction with Eclipse planar dose and trajectory log files can eliminate the need to physically measure VMAT patient QA plans. The method is robust and can effectively identify fields with potential errors. Furthermore, the RadCalc Image Analysis Tool allows easy manipulation of the resolution of dose and intensity maps for a more precise comparison than is possible with MapCheck measurements.

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