13C, SPIRAL CHEMICAL SHIFT IMAGING, SPECTRAL UNDERSAMPLING, PYRUVATE, LACTATE

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Introduction: The development of hyperpolarized, metabolically active MRI agents presents both unprecedented opportunities as well as new technical challenges. While it theoretically permits in vivo imaging of not only the substrate, but also downstream metabolic products, the decay of the longitudinal magnetization demands fast acquisition schemes. The need for speed in combination with the sparse spectra which can occur in the application of hyperpolarized 13C metabolic imaging makes spiral chemical shift imaging (spCSI) an ideal candidate for this application. Methods and Discussion: The implemented sequence exploits sparse spectra and prior knowledge of resonance frequencies to reduce the measurement time by undersampling the data in the spectral domain. As a consequence, multiple reconstructions of a given data set have to be computed in which only components with frequencies within a certain bandwidth are reconstructed in-focus while other are severely blurred (spectral tomosynthesis). The sequence was tested at 3 T on a phantom containing solutions of alanine (Ala), lactate (Lac), and pyruvate-pyruvate hydrate C1-C2 ester (with two resonances, PPE1 and PPE2) at thermal equilibrium polarization, all enriched to 99% 13C in the C1 carbonyl positions. Spiral CSI with a single spatial interleaf (single-shot spCSI) and 3 interleaves (3-shot spCSI), respectively, were compared to phase-encoded CSI (FIDCSI). Metabolic maps of all four resonances for 3-shot spCSI and of PPE1 and PPE2 for single-shot spCSI demonstrate similar resolution and localization properties as the FIDCSI images. Metabolic maps of Ala and Lac for single-shot spCSI contain minor artifacts due to signal overlap of aliased resonances. Funding Sources " P41 RR009784, Center for advanced MR Technology at Stanford, Gary H. Glover, 01/01/1995-5/31/2010 " R01 CA048269, Magnetic Resonance Spectroscopic Neoplasm Imaging, Daniel M. Spielman, 7/23/1990-7/31/2006 " R01 AA012388, In Vivo Diffusion and Spectroscopic Brain Imaging in Alcoholism, Adolf Pefferbaum, 8/1/2000-6/30/2010 Relevant publications " D. Mayer, Y.S. Levin, R.E. Hurd, G.H. Glover, D.M. Spielman Fast Metabolic Imaging of Systems with Sparse Spectra: Application for Hyperpolarized 13C Imaging, Magn. Reson. Med., in revision. " D. Mayer, Y.S. Levin, R.E. Hurd, G.H. Glover, D.M. Spielman Fast Metabolic Imaging of Systems with Sparse Spectra: Application for Hyperpolarized 13C Imaging, Proc ISMRM, 14th Annual Meeting, Seattle, 2006, submitted.