Temperature measurements in MRI using ferromagnetic particles
Karl F. Stupic, Janusz H. Hankiewicz, Zbigniew Celinski, Robert E. Camley
We explore the possibility of using small ferromagnetic particles with a strong temperature- dependent magnetization to produce temperature maps using magnetic resonance imaging (MRI). We present the first experimental results showing that the 1H nuclear magnetic resonance (NMR) linewidth and the MR image intensity of aqueous samples doped with gadolinium particles are strongly temperature-dependent in ranges near human body temperature. NMR spectra linewidths and shades of gray in images taken with Gd particles present can be calibrated to obtain a spatial map of temperature or to report the achievement of a certain temperature. The estimated accuracy of the temperature determination is ±1.2 oC at 24 oC for the MR image intensity. While Gd is a promising material for temperature measurements in MRI because its Curie temperature is close to body temperature, other materials can be designed to give even better performance.