Abstract:

OBJECTIVE In Patient Quality Assurance measurements for Intensity Modulated Radiation Therapy, this study aimed to investigate the dosimetric differences between the calculated and measured values when the standard dosimetric equipment contains the different density materials. METHODS In this study, a setup that can be used for both absolute dose and planar dose distribution is considered aimed to investigate the effects of the selected grid size value in the treatment planning system on the Monitor Unit, 2D array gamma evaluation and absorbed dose measurements. Also, the effects of using different "distance to agreement" values and the effects of using cylindrical/inhomogeneous phantom instead of square/homogeneous on 2D array gamma evaluation and absorbed dose measurements were investigated. RESULTS The considerable difference between the calculated dose and measured dose for grid size 0.1 cm was found to be 2.96% for the square/homogeneous phantom and 5.75% for the cylindrical/inhomogeneous phantom. According to the 3%/2 mm criterion, Setup1 allowed treatment with 98.76%, whereas this value was below our acceptance limit with 88.39% for Setup 2. CONCLUSION In addition to the standard IMRT patient QA procedure, we are of the opinion that the use of clinically different dosimetric equipment provides an idea of the control of different grid size values of TPS calculation algorithms.

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