Journal of Medical Physics and Applied Sciences

Evaluation of Consistency of Flattening Filter Free Beam using Automated and Image-Based Tool

Abstract Aim: Analysis of consistency of True Beam for Six months using Automated and Integrated Image-Based tool. Methods and materials: Data acquisition comprises a series of 40 images (12 KV and 28 MV Images) acquired at predefined positions without and with ISOCAL phantom in the beam and with predefined MLC pattern settings. Machine Performance Check utilizes a series of KV and MV images of the ISOCAL phantom to assess: Treatment isocenter size and its coincidence with MV and KV imager, positioning accuracy of the imaging systems, accuracy of collimator and gantry angles, accuracy of jaw and MLC leaf positions, accuracy of couch positioning. Six months data was taken and calculated maximum, minimum and average of each parameter. Results: Results were analyzed for 6MV photon beam. Treatment isocenter size was between 0.53 mm and 0.33 mm (threshold of ± 0.50 mm). Coincidence of MV and KV imaging isocenters was within 0.49 mm to 0.14 mm and 0.36 mm to 0.16 mm. Positioning accuracy of MLC was within 0.3 mm to 0.37 mm; accuracy of jaws in mm was within -0.91 to -0.93, -0.02 to -0.94, 0.12 to -0.19, and 0.42 to 0.14 for X_1, X_2, Y_1 and Y_2 jaws respectively. Absolute gantry accuracy was within 0.1 to -0.06 and relative gantry accuracy was with in 0.12 and -0.1 degrees respectively. Couch accuracy for lateral, longitudinal, vertical, rotation, rotation induced couch shift in mm was within -0.4 to - 0.66 , -0.07 to -0.25, -0.06 to -0.18, 0.01 to -0.09, and 0.63 to 0.29 respectively. Conclusion: Analysis of our six months data shown that the consistency of True Beam is satisfactory. Its values are in close agreement with the routine QA programme in our department and satisfy all recommendations under

Author(s):

Sadaf Shafi Gadoo,Muralidhar K. R,Upendar Rao C,Shrinivas P,Mudasir Ashraf,Mudasir Ashraf,Anu Radha

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