A model for the dynamics of spins 3/2 in biological media: signal loss during radiofrequency excitation in triple-quantum-filtered sodium MRI.
We have derived the differential equations that describe the dynamics of spin-3/2 nuclei in the presence of radiofrequency (RF) fields and both static and fluctuating quadrupolar interactions. The formalism presented was used to predict the sodium triple-quantum-filtered (TQ-filtered) signal loss in a whole-body scanner, where the widths of the hard 90 degrees RF pulses are on the same order of magnitude as the transverse relaxation times. A small piece of bovine nasal cartilage, known for exhibiting residual quadrupolar splittings, was used to test the theory. The sample was modeled as consisting of small domains, each characterized by a static quadrupolar interaction constant, with an overall Gaussian distribution across the sample. An increase of about 15% in the TQ-filtered signal strength, as the 90 degrees RF pulse width was decreased from 500 to 100 micros, was predicted and demonstrated experimentally for this particular sample.
Hancu
I
I
Department of Physics, University of Pittsburgh, Pittsburgh, Pennsylvania 15213, USA.
van der Maarel
J R
JR
Boada
F E
FE
D000818:Animals; D002356:Cartilage / Q000737:chemistry*; D002417:Cattle; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008433:Mathematics; D011846:Radio Waves; D012964:Sodium / Q000737:chemistry*
D012964:Sodium