Dosimetric evaluation of IMRT plan for homogenous and inhomogeneous medium using AAPM TG-119 protocol

10th International Seminar on Medical Physics; 1st AMDI International Oncology Symposium

物理学;医药卫生

Fatimah, L.A.N.^1 ; Wibowo, W.E.^2 ; Pawiro, S.A.^2

Department of Physics, Faculty of Mathematics and Natural Sciences, Universitas Indonesia, Depok, Indonesia^1

Department of Radiotherapy, National General Hospital Dr. Cipto Mangunkusumo, Jakarta, Indonesia^2

关键词: Assessment criteria;    Conformity index;    Dose measurement;    Dose verification;    Homogeneity index;    Inhomogeneous medium;    Inhomogeneous phantom;    Planning objectives;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/851/1/012022/pdf
DOI  :  10.1088/1742-6596/851/1/012022

学科分类：卫生学

来源: IOP

【 摘 要 】

The American Association of Physicists in Medicine (AAPM) TG-119 protocol has been applied for dose verification in IMRT technique. However, some criteria in the protocol need to be verified for inhomogeneous medium and small volume targets. Hence, the purpose of this study was to verify the assessment criteria of dose verification in AAPM TG-119 for inhomogeneous medium and small volume targets. The work has been conducted by dose verification for homogeneous (phantom A) and inhomogeneous phantoms (phantom B and C) on two geometrical targets: C-shape and circular targets. The targets were simulated using 7 static dMLC IMRT fields at two different depths of 5 g/cm2and 10 g/cm2. The dose optimisation and calculation were done by using Pinnacle3for 6 MV photons beam. The planning objectives were set according to AAPM TG-119 parameters. The plan analysis was conducted by Conformity Index and Homogeneity Index. The point dose measurements were conducted with Exradin A16, Semiflex 0.125cc, and Gafchromic EBT3. The plan results show that CI for C-shape target is in the range of 0.710-0.999 at 10 g/cm2depth and 0.691-1.613 at 5 g/cm2. In addition, HI for C-shape and circular were in the range of 6.3%-58.7% and 5.4%-87.1% for 10 g/cm2depth. The measurement results show that the dose measurement at inhomogeneous medium and small volume targets are much lower than the criteria in AAPM TG-119. In conclusion, the criteria in the AAPM TG-119 cannot be fully implemented for inhomogeneous medium and small volume targets.