TITLE:
Real Time MR Thermometry Using Tm-DOTMA
AUTHORS:
Bu S. Park, Martin J. Lizak, Leonardo M. Angelone, Sunder S. Rajan
KEYWORDS:
Tm-DOTMA, CSI, PRF, Real-Time, FDTD, RF, Temperature Mapping
JOURNAL NAME:
Journal of Electromagnetic Analysis and Applications,
Vol.7 No.4,
April
24,
2015
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. Using a
heating pre-scan, the Tm-DOTMA 2D-CSI allowed better qualitative visualization
of the temperature changes around the titanium screw compared with water phase
shift thermometry. Numerical
electromagnetic field simulations were also conducted for the evaluation of
orientation dependency using the copper wire in 4.7 T (200 MHz). Thermometry
approach using Tm-DOTMA can detect smaller temperature changes with decreased
scanning time resulting in real-time and sensitive temperature mapping.