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Evaluation of a New Commercially Device for Patient Specific IMRT QA

S Stathakis

S Stathakis1*, P Myers1, C Esquivel1, A Gutierrez1, P Mavroidis2, N Papanikolaou1, (1) Cancer Therapy and Research Center, San Antonio, TX, (2) Karolinska Institutet & Stockholm University, Stockholm, Sweden

SU-E-T-361 Sunday 3:00:00 PM - 6:00:00 PM Room: Exhibit Hall

Purpose: To evaluate the performance of a new system for patient specific IMRT QA.

Methods: The new Octavius 4D system and its accompanying software (Verisoft) by PTW were used to compare calculated and measured dose distributions for ten (n=10) patients' plans. Five IMRT and five SmartArc plans were used for the comparison. All plans were optimized using the Pinnacle treatment planning system and the plans and their respective verification plans were calculated using collapsed cone convolution superposition dose calculation algorithm. The verification plans were evaluated using the gamma index and also by visually inspecting the dose profiles and isodose distributions.
The Verisoft IMRT QA is able to reconstruct the 3D dose from individual planar measurements and hence provide comparison for transverse, sagittal, and coronal planes.

Results: The gamma index values varied from 92.1 to 99.2% when the coronal plan was only evaluated. Because of the ability of the system to compose the dose distribution from the individual measurements, comparison of the sagittal, transverse planes as well as 3d dose distributions were available. The gamma index values varied from 88.3 to 99.5% for different planes while the 3D gamma index values ranged from 85.0 to 99.5%.

Conclusions: The new phantom for patient specific IMRT QA in this study can effectively be used for clinical use. The ability of the software to compute 3D dose distribution from all measurements taken is powerful tool that aids the physicist to evaluate the verification plan by providing 3D information not available from other commercial systems. Further investigation of the system's dose reconstruction algorithm is necessary to determine its accuracy.

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