An investigation into the effect of magnetic resonance imaging (MRI) echo time spacing and number of echoes on the sensitivity and dose resolution of PAGATUG polymer-gel dosimeter

Background: There are various methods to read out responses of a polymergel dosimeter, among which the Magne c Resonance Imaging (MRI) technique is the most common one. Op mizing imaging protocols can have significant effect on the sensi vity and the dose resolu on of polymer gel dosimeters. This study has inves gated the effects of the number of echoes (NOE) and the echo me spacing (ES) parameters on the response of the PAGATUG polymer gel dosimeter. Materials and Methods: The polymer gel dosimeters were produced under the normal atmospheric condi on, then irradiated using a 60 Co clinical radia on source. The polymer gel dosimeters were imaged using MRI technique with different imaging protocols. A0erwards, the effects of the ES and the NOE on the R2-sensi vity and the dose resolu on of PAGATUG polymer gel dosimeter have been inves gated. Results: Results showed that the sensi vity decreased with increasing NOE. However, it was found that the resolu on got be3er with increasing NOE. Furthermore, the inves ga on of signal intensity decay curve showed that the R2 values in NOE less than 5 was less reliable. According to the results, no significant difference were found between the sensi vi es of the polymer gel dosimeters which were imaged with different ESs, except for ES=22 ms. However, dose resolu on suffered from ES increasing. Conclusion: Dosimetric parameters of PAGATUG polymer gel dosimeter reaches to their op mum values by imaging with ES=25ms and NOE=10.