الفهرس 
Chapter 1 Introduction and literature ReviewIntroduction and literature ReviewIntroduction and literature ReviewIntroduction and literature ReviewIntroduction and literature ReviewIntroduction and literature ReviewIntroduction and literature ReviewIntroduction and literature ReviewIntroduction and literature ReviewIntroduction and literature ReviewIntroduction and literature ReviewIntroduction and literature ReviewIntroduction and literature ReviewIntroduction and literature ReviewIntroduction and literature ReviewIntroduction and literature ReviewIntroduction and literature ReviewIntroduction and literature ReviewIntroduction and literature ReviewIntroduction and literature ReviewIntroduction and literature ReviewIntroduction and literature ReviewIntroduction and literature ReviewIntroduction and literature ReviewIntroduction and literature ReviewIntroduction and literature ReviewIntroduction and literature ReviewIntroduction and literature ReviewIntroduction and literature ReviewIntroduction and literature ReviewIntroduction and literature ReviewIntroduction and literature ReviewIntroduction and literature ReviewIntroductionOnly 14 pages are availabe for public view
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Abstract
Brain tumor is a heterogeneous tumor and surrounding organs that have less tolerance to radiation.
A very powerful one therapies for brain glioma is radiation therapy, which kills a high percentage of tumor cells inside the PTVs (planned treatment volumes) while causing least harm to healthy tissues.
The most cutting-edge form of radiotherapy is called VMAT or volumetric modulated arc therapy, which uses radiation arcs rather than single beams utilized in IMRT and 3D-CRT.
The aim of the current work is to compare dosimetrical and radiobiological indices of treatment plans for brain tumor using coplanar VMAT and non- coplanar VMAT techniques to choose and evaluate accurate and optimal technique for brain tumor patients.
Twenty cases with the brain tumors that previously diagnosed were performed for the treatment planning study. The cases are planned by using the coplanar and non-coplanar VMAT techniques and optimized to evaluate and compare the dosimetrical and radiobiological parameters related to PTV dosage coverage and sparing of OARs.
The total dose of CO-VMAT and NC-VMAT plans is 60 Gray in 30 fractions during a single phase with a daily dose of 2 Gray.
The evaluation of treatment plan for each case was depended on target coverage, gradient, homogeneity, conformity, monitor units, quality factor, dose statistics of normal tissue and probabilities about controlling tumor along with surrounding organs complications.
In comparison study showed CO-VMAT and NC-VMAT techniques gave a similar {Homogeneity index HI (1.10, 1.09), Modified homogeneity index MHI (1.06, 1.05), Conformity index CI (0.90, 0.89) and Quality factor QF (2.496, 2.502)}. NC-VMAT was the higher in {Target coverage index TCI (0.88), Prescription isodose to target volume PITV (1.00) and Conformity number CN (0.78)} and the lower in {Gradient index GI (2.94), Gradient measure GM (1.52)}, while CO-VMAT was the lower in Monitor units MUs (322.70).
The NC-VMAT was the best in sparing of brainstem, chiasm, left optic nerve, right optic nerve, left eye, right eye, left lens, right lens, left cochlea, right cochlea, pituitary compared to the CO-VMAT. Furthermore, the overall maximum and mean doses statistics of CO-VMAT and NC-VMAT still within the dosage tolerance constraints.
On the other hand, this study showed that the critical organ scoring index COSI, modified COSI, tumor control probability TCP (81.56%) and complication free tumor control probability P+ (81.09%) were large in NC-VMAT and normal tissue complication probability NTCP was less in NC-VMAT.
In conclusion, NC-VMAT technique uses in cases of brain tumors that require to more spare OARs which close to the tumor or part of it is located within the tumor due to it turned out to be the best technique in providing more protection for critical structures from radiation and that through minimizing doses for them much less than the permissible doses limits compared to CO-VMAT.