Introduction: Three physical conditions caused an external beam designated as a small field. The first is the loss of lateral charged particle equilibrium. The second is the effect of collimators on the primary photon source occlusion. The third condition is the size of the detector which is large compared to the field size. The most obvious perturbation effects in last condit...

background: the purpose of this study was to evaluate the dependency of magica polymer gel dosimeter response (r2) on different electron energies as well as on different mean dose rate for a standard clinically used linear accelerator. materials and methods: the sensitivity of the dosimeter was represented by the slope of calibration curve in the linear region measured for each modality. a cali...

Background: There are various methods to read out responses of a polymer-gel dosimeter, among which the Magnetic Resonance Imaging (MRI) technique is the most common one. Optimizing imaging protocols can have significant effect on the sensitivity and the dose resolution of polymer gel dosimeters. This study has investigated the effects of the number of echoes (NOE) and the echo time spacing (ES...

Background: The purpose of this study was to evaluate the dependency of MAGICA polymer gel dosimeter response (R2) on different electron energies as well as on different mean dose rate for a standard clinically used linear accelerator. Materials and Methods: The sensitivity of the dosimeter was represented by the slope of calibration curve in the linear region measured for each modalit...

background: in this study the basic radiation properties of n-isopropylacrylamaide polymer gel dosimeter were determined together with verification of its soft tissue equivalency. materials and methods: the nipam gel was prepared and irradiated approximately 2 h after manufacturing. the magnetic resonance (mr) images were made 24 h after irradiation. the nuclear magnetic resonance (nmr) respons...

background: in this work investigation of the normoxic pagat polymer gel dosimeter such as sensitivity, the r2-dose response with post time and the percentage depth dose (pdd) of pagat polymer gel dosimeter have been undertaken. materials and methods: using mri, the formulation to give the maximum change in the transverse relaxation rate r2 was determined to be 4.5% n,n'-methylenbis- acryl...

Background: In this study the basic radiation properties of N-isopropylacrylamaide polymer gel dosimeter were determined together with verification of its soft tissue equivalency. Materials and Methods: The NIPAM gel was prepared and irradiated approximately 2 h after manufacturing. The magnetic resonance (MR) images were made 24 h after irradiation. The nuclear magnetic resonance (NMR) respons...

background: an effective polymer gel dosimeter can be fabricated by varying the composition of its chemical components. materials and methods: the magat gel dosimeter formulations that used different compositions of methacrylic acid (maa) and gelatin were extensively investigated in the present study according to the r2–dose response and r2–dose sensitivity. the irradiation of magat gel was per...

The purpose of this study was to evaluate dependence of PAGAT polymer gel dosimeter 1/T2 on different electron and photon energies for a standard clinically used Co therapy unit and an electa linear accelerator.Using MRI, the formulation to give the maximum change in the transverse relaxation rate R2(1/T2) was determined to be 4.5% N,N'-methylen-bis-acrylamide(bis), 4.5% acrylamid(AA), 5% gelat...

Background: In this work investigation of the normoxic PAGAT polymer gel dosimeter such as sensitivity, the R2-dose response with post time and the percentage depth dose (PDD) of PAGAT polymer gel dosimeter have been undertaken. Materials and Methods: Using MRI, the formulation to give the maximum change in the transverse relaxation rate R2 was determined to be 4.5% N,N'-methylenbis- ...