Making, storing and using nuclear spin hyperpolarization

PHYS 240

Valerie A. Norton1, Jason E. Ollerenshaw1, Eduard Y. Chekmenev1, Jan B. Hövener2, Kent Harris2, Lynne S. Batchelder3, Pratip Bhattacharya2, Brian D. Ross2, and Daniel P. Weitekamp, weitekamp@caltech.edu1. (1) A.A. Noyes Laboratory of Chemical Physics, California Institute of Technology, 127-72, Pasadena, CA 91125, (2) Enhanced MR Laboratory, Huntington Medical Research Institutes, Pasadena, CA 91105, (3) Cambridge Isotope Laboratories, Andover, MA 01810
We describe several experimental and theoretical developments aimed at fast, portable production of small molecules capable of delivering spin order into complex chemical environments. The PASADENA (parahydrogen and synthesis allow dramatically enhanced nuclear alignment) method of hyperpolarization is complete in several seconds even in aqueous solvent and over a wide range of pH. We describe progress with a portable low field device for the molecular addition of dihydrogen and production of 13C polarizations of ~20% at sites with long T1, including the first such demonstration with a metabolite, 1-13C succinate (Chekmenev et al. JACS, 2008). Recent insights into efficient spin order transfer by coherent averaging of the network of scalar couplings promises to extend this success to diverse molecules of interest as MRI metabolic contrast agents, including those for which slow spin conversion among proton states extends the storage of spin order. Optimization of fast magnetic resonance imaging to determine the transport and metabolic fate of the hyperpolarized species is aided by a simulation combining multiple rf pulses and chemical exchange, thus modeling the signal transients unique to an initial state of spin and chemical disequilibrium.