Real Time MR Thermometry Using Tm-DOTMA

Abstract

We present results of real-time and sensitive MR Thermometry (MRT) using a paramagnetic lanthanide complex thulium 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetramethyl-1,4,7,10-tetraa-cetate (Tm-DOTMA) to study radio frequency (RF) heating induced by a copper wire and a titanium bone screw in an agarose gel phantom. The temperature dependent chemical shift coefficient (TDCSC) of the methyl resonance was found to be 0.7 ± 0.03 ppm/˚C in agarose gel. The methyl protons of Tm-DOTMA were imaged using 2D chemical shift imaging (CSI) and 3D phase mapping methods (PMM), approximately 7 sec long, and compared with conventional water proton resonance frequency (PRF) method. Two RF-induced heating approaches were tested: 1) using a prescan before the MRT; or 2) using the heating caused by the imaging pulse during continuous imaging. Both approaches allowed detection of temperature changes which are less than 1˚C and continuously mapping temperature changes around the copper wire.