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American Journal of Neuroradiology
DOI 10.3174/ajnr.A1790
METHODOLOGIC PERSPECTIVES
Hyperpolarized MR Imaging: Neurologic Applications of Hyperpolarized Metabolism
From the Huntington Medical Research Institutes, Pasadena, California; and Rudi Schulte Research Institute, Santa Barbara, California.
Please address correspondence to Brian D. Ross, MD, 10 Pico St, Pasadena, CA 91105; e-mail: Bdross.hmri{at}gmail.com
SUMMARY: Hyperpolarization is the general term for a method of enhancing the spin-polarization difference of populations of nuclei in a magnetic field. No less than 5 distinct techniques (dynamic nuclear polarization [DNP]; parahydrogen-induced polarization–parahydrogen and synthesis allow dramatically enhanced nuclear alignment [PHIP-PASADENA]; xenon/helium polarization transfer; Brute Force; 1H hyperpolarized water) are currently under exhaustive investigation as means of amplifying the intrinsically (a few parts per million) weak signal intensity used in conventional MR neuroimaging and spectroscopy. HD-MR imaging in vivo is a metabolic imaging tool causing much of the interest in HD-MR imaging. The most successful to date has been DNP, in which carbon-13 (13C) pyruvic acid has shown many. PHIP-PASADENA with 13C succinate has shown HD-MR metabolism in vivo in tumor-bearing mice of several types, entering the Krebs–tricarboxylic acid cycle for ultrafast detection with 13C MR imaging, MR spectroscopy, and chemical shift imaging. We will discuss 5 promising preclinical studies: 13C succinate PHIP in brain tumor; 13C ethylpyruvate DNP and 13C acetate; DNP in rodent brain; 13C succinate PHIP versus gadolinium imaging of stroke; and 1H hyperpolarized imaging. Recent developments in clinical 13C neurospectroscopy encourage us to overcome the remaining barriers to clinical HD-MR imaging.