Fast MRI of RF heating via phase difference mapping.
A method is presented for the rapid acquisition of temperature maps derived from phase difference maps. The temperature-dependent chemical shift coefficients (TDCSCs) of various concentrations of aqueous cobalt and dysprosium-based compounds were measured. The largest TDCSC calculated was for 100 mM DyEDTA, which had a TDCSC of -0.09 PPM/K; 160 mM CoCl2 had a TDCSC of -0.04 PPM/K. These temperature-dependent chemical shifts (TDCSs) result in phase changes in the MR signal with changing temperature. Agarose phantoms were constructed with each paramagnetic metal. A fast gradient-echo (FGRE) MR image was acquired to serve as the baseline image. A "test" MRI procedure was then performed on the phantom. Immediately afterwards, a second FGRE MR image was acquired, serving as the probing image. Proper image processing as a phase difference map between the probing image and the baseline image resulted in an image which quantitatively described the temperature increase of the phantom in response to a particular "test" imaging experiment. Applications of this technique in assessing the safety of pulse sequences and MR coils are discussed.
Shapiro
Erik M
EM
Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania, USA. shapiroE@ninds.nih.gov
Borthakur
Arijitt
A
Shapiro
Michael J
MJ
Reddy
Ravinder
R
Leigh
John S
JS
D055592:Biophysical Phenomena; D001703:Biophysics; D003035:Cobalt; D004419:Dysprosium; D006358:Hot Temperature; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009682:Magnetic Resonance Spectroscopy; D019047:Phantoms, Imaging; D011846:Radio Waves; D012685:Sepharose
D004419:Dysprosium; D003035:Cobalt; D012685:Sepharose