MANAGEMENT OF A ROTATIONAL DETECTOR ARRAY IN IMRT COMMISSIONING TESTS

Introduction: After an instalation of a radiotherapy machine, physicists need to perform some procedures known as commissioning test. To become available to be used in a IMRT planning system, these results need to be fited through a process called modelling. This step ends when the difference between modellings and direct measurements become lower than specific values accepted by international commitees. Goal. Use a Rotational Detector Array to perform an Acceptance Modelling Test of a linear accelerator using standard irradiation fields provided from factory. Methods: The archive is named FullPackage and includes 34 standard statics and dynamics fields. All of them were tested in a calibrated Rotational Detector Array. The heterogeneity of layers was taked in consideration. Two energies of photons were validated, 6 and 10 MV. Results and Conclusion: The origin of measurements both the commissioning measurements and calibration of detector array come from the same set up in linear accelerator vertically down. So, this array is elegible to quickly do this essencial job. The used Rotational Array take all the measurements in a perpendicular incidence, decreasing of this way the influence of uncertainties from oblique irradiation of detectors. The size of calculation matrix in Treatment Planning System is also crucial in results, considering that the device has a fixed space among detectors. Small grid size increases uncertainties in comparision analysis, because it generates a lot of virtual check dose points that couldn‘t be verified at the same time in device. Take it in consideration, 70% of comparision were approved with gamma index 3%/3mm. Weak points showed in this methodology can be corrected through the interpolation of some measurements shifted a known distance from center of device. Therefore, we consider it approved for intended goal.