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Evaluation of New Pre-Treatment In-Air Patient Specific QA Software for TomoTherapy Treatments


L Levinson

L Levinson1*, Q Chen1, K Ding1, W Renner2, S Benedict1, P Read1, (1) University of Virginia Health Systems, Charlottsville, VA, (2) Math Resolutions, LLC, Columbia, MD

SU-E-T-26 Sunday 3:00:00 PM - 6:00:00 PM Room: Exhibit Hall

Purpose: Math Resolutions, LLC, has extended their Dosimetry Check quality assurance software to include TomoTherapy treatments. Data collected from TomoTherapy's MVCT detectors is processed and compared to the planned treatment dose allowing for pre-treatment QA without the use of phantoms and other detectors. This study presents an overview of our experience at the University of Virginia developing, implementing, and verifying this novel QA strategy.
Methods: Low modulation and high modulation cheese phantom plans as well as patient plans (prostate, GYN, and vertebra) were used to test the Dosimetry Check in-air software. For all evaluations the treatment table was removed from the XML file of each plan using software provided by Accuray and the resulting in-air calibration plan was delivered. The exit detector sinogram was extracted from the machine and imported into Dosimetry Check along with the TomoTherapy calculated planned dose. The fluence maps were reconstructed and used to recalculate the dose.
Results: The percent difference between the planned dose and the dose calculated from the exit detectors by Dosimetry Check ranged between 0.62% for a simple low modulation cheese phantom plan with a cylindrical target to 7.3% for a high modulation 2.5cm prostate plan. The gamma indices reported range from 94.7% to 97.8% <1 over the overall calculation area for the plans tested using a gamma of 3% and 3mm. For the area receiving over 80% of the prescribed dose, the gamma ranged from 80.7% to 92.9% <1.
Conclusions: The results of our investigation of Math Resolutions' new product in development, Dosimetry Check's pre-treatment in-air QA software, demonstrate that it has the potential be a very useful and practical tool for TomoTherapy QA. Further testing is being performed in which various errors are intentionally introduced in the delivered dose to test the limits of Dosimetry Check's sensitivity.


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