Enhanced hyperpolarized chemical shift imaging based on a priori segmented information.

Abstract

The purpose of the study was to develop an approach for improving the resolution and sensitivity of hyperpolarized 13 C MRSI based on a priori anatomical information derived from featured, water-based 1 H images. A reconstruction algorithm exploiting 1 H MRI for the redefinition of the 13 C MRSI anatomies was developed, based on a modification of the spectroscopy with linear algebraic modeling (SLAM) principle. To enhance 13 C spatial resolution and reduce spillover effects without compromising SNR, this model was extended by endowing it with a search allowing smooth variations in the 13 C MR intensity within the targeted regions of interest. Experiments were performed in vitro on enzymatic solutions and in vivo on rodents, based on the administration of 13 C-enriched hyperpolarized pyruvate and urea. The spectral images reconstructed for these substrates and from metabolic products based on predefined 1 H anatomical compartments using the new algorithm, compared favorably with those arising from conventional Fourier-based analyses of the same data. The new approach also delivered reliable kinetic 13 C results, for the kind of processes and timescales usually targeted by hyperpolarized MRSI. A simple, flexible strategy is introduced to boost the sensitivity and resolution provided by hyperpolarized 13 C MRSI, based on readily available 1 H MR information.