A preliminary study of the thermal measurement with nMAG gel dosimeter by MRI

The methacrylic acid (nMAG) gel dosimeter is an effective tool for 3-dimensional quality assurance of radiation therapy. In addition to radiation induced polymerization effects, the nMAG gel also responds to temperature variation. In this study, we proposed a new method to evaluate the thermal response in thermal therapy using nMAG gel and magnetic resonance image (MRI) scans. Several properties of nMAG have been investigated including the R₂ relaxation rate, temperature sensitivity, and temperature linearity of the thermal dose response. nMAG was heated by the double-boiling method in the range of 37–45 °C. MRI scans were performed with the head coil receiver. The temperature to R₂ response curve was analyzed and simple linear regression was performed with an R-square value of 0.9835. The measured data showed a well inverse linear relationship between R₂ and temperature. We conclude that the nMAG polymer gel dosimeter shows great potential as a technique to evaluate the temperature rise during thermal surgery. - Highlights: • Using gel dosimeter the thermal response is evaluated. • The nMAG gel has a linear response between 37 °C and 45 °C. • Using gel dosimeter the thermal damage of normal tissue during thermal surgery may be evaluated