The Effects of Magnetic Field Strength on MAGICA Polymer Gel Dosimeter Response

The most considerable advantage of gel dosimeters is their unique ability to determine three dimensional dose distribution. Polymer gel dosimeters are, in fact, monomers distributed in a gelling matrix. Upon the irradiation, these monomers convert to polymers and as a result some of their detectable properties will be changed. One of them is the magnetic property which is detectable by the use of the MRI photography. In this research, the effect of magnetic field strength and echo numbers of a MRI system on the response of the MAGICA gel dosimeters was investigated. Consequently, after irradiation of the MAGICA polymer gel dosimeters, this dosimeter was imaged by 0.5T and 1.5T MRI systems with 8 and 32 echo, respectively. Sensitivity of the gels imaged by the 1.5T and 0.5T systems were 0.17±0.005 Gy/s and 0.16±0.005 Gy/s, respectively. The R2 values obtained from 0.5 T system were found to be higher compared with the 1.5T system in all the measured doses. Up to dose rate of 17.5Gy the resolution difference of the 1.5T and 0.5T imaged gels was ignorable and beyond this point this difference was increased notably. It can be concluded that when the absorbed dose is applied up to 17.5Gy the 0.5T MRI system is suitable but beyond this dose the 1.5T system is recommended.