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A Software Tool for the Efficient Correction and Analysis of IMRT QA Experimental Data Using MatriXX

M Wagar

M Wagar1*, P Zygmanski1,2, R Cormack1,2, (1) Dana-Fraber/Brigham and Women's Cancer Center, Boston, MA, (2) Harvard Medical School, Boston, MA

SU-E-T-199 Sunday 3:00PM - 6:00PM Room: Exhibit Hall

Purpose: The rationale for developing this software was to address shortcomings found while using OmniPro-I'mRT software to evaluated patient specific IMRT QA measurements taken with MatriXXEvolution 2D ion chamber array. Our software addresses three major issues. It calculates average doses within each ion chamber of the array using 3D TPS DICOM field-by-field doses exported as input, corrects the resulting doses to account for gantry angle dependence of Matrixx, and automates the analysis of the measured data resulting in a concise report document ideal for patient electronic medical records (EMR).

Materials/Methods: The software was developed in MATLAB to improve and streamline analysis of patient-specific IMRT QA. It compares measured Matrixx doses to average doses within each ion chamber of the array, which are computed from 3D DICOM doses exported from TPS for each field. A correction factor is applied to the TPS doses to account for angular dependence. The Data is automatically evaluated using the 2D gamma analysis, evaluating a range of passing criteria (3%,4%,5%). This software allows for user-defined passing criteria and automated reporting of quantitative results, eliminating potential user errors. A single-sheet report is generated displaying patient information, planar dose distributions, x-y-profiles, and gamma plot noting the pixel based passing criteria. The effect of misalignment in direction perpendicular to detector plane is simulated by allowing a non-zero shift along that direction.

Results: This home-built IMRT QA analysis tool gives a clear quantitative answer based on the user defined criteria. The implementation of an angular dependence correction and the averaging over the volume of the ion chambers improves the accuracy of the analysis accounting for ion chamber size (~5mm x 5mm x5mm) and spacing (~7mm x 7mm)

Conclusion: Though this tool does not replace the commercial software completely, it improves the accuracy of the analysis and streamlines the process.

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