Aqueous urea as a model system for bi-exponential relaxation.
OBJECTIVE
To evaluate the utility of aqueous urea, doped inner- and outer-sphere relaxation agents, as an adjustable two-component model system.


METHODS
T2 was measured from 12 molal urea mixtures at pH 7.0 with varying amounts of the MnCl2 and FeO(1.44) (Feridex, Berlex Inc, Montville, NJ).


RESULTS
Bi-exponential relaxation was observed, with rates that were bilinearly related to [MnCl2] and [FeO(1.44)]. FeO(1.44) had comparable relaxivities on both urea and water, while MnCl2 relaxivity was > 15x larger for water than for urea.


CONCLUSIONS
Aqueous urea, doped with inner- and outer-sphere contrast agents, is a two-compartment model system, which can be exhibit a wide range of different T2s and signal fractions.
Horch
R Adam
RA
Department of Biomedical Engineering, Vanderbilt University School of Engineering, Nashville, TN 37232-2310, USA.
Does
Mark D
MD
D008279:Magnetic Resonance Imaging; D009682:Magnetic Resonance Spectroscopy; D008956:Models, Chemical; D012996:Solutions; D014508:Urea / Q000737:chemistry*; D014867:Water / Q000737:chemistry
D012996:Solutions; D014867:Water; D014508:Urea