Rıdvan ÜNAL, Aysun İNAL, İsmail Hakkı SARPÜN

A Different Approach to Intensity Modulated Radiation Therapy Patient QA Measurements about Dosimetric Equipment

OBJECTIVEIn Patient Quality Assurance measurements for Intensity Modulated Radiation Therapy, this studyaimed to investigate the dosimetric differences between the calculated and measured values when thestandard dosimetric equipment contains the different density materials.METHODSIn this study, a setup that can be used for both absolute dose and planar dose distribution is consideredaimed to investigate the effects of the selected grid size value in the treatment planning system on theMonitor Unit, 2D array gamma evaluation and absorbed dose measurements. Also, the effects of usingdifferent “distance to agreement” values and the effects of using cylindrical/inhomogeneous phantominstead of square/homogeneous on 2D array gamma evaluation and absorbed dose measurements wereinvestigated.RESULTSThe considerable difference between the calculated dose and measured dose for grid size 0.1 cm wasfound to be 2.96% for the square/homogeneous phantom and 5.75% for the cylindrical/inhomogeneousphantom. According to the 3%/2 mm criterion, Setup1 allowed treatment with 98.76%, whereas thisvalue was below our acceptance limit with 88.39% for Setup 2.CONCLUSIONIn addition to the standard IMRT patient QA procedure, we are of the opinion that the use of clinicallydifferent dosimetric equipment provides an idea of the control of different grid size values of TPS calculationalgorithms.

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