Improved Acquisition Methods for Hyperpolarized Carbon-13 Magnetic Resonance Imaging
Magnetic resonance imaging with hyperpolarized 13C-labeled compounds via dynamic nuclear polarization (DNP) has been used to non-invasively study metabolic processes in vivo. This method provides a transient signal enhancement of more than 10,000 fold compared to imaging 13C compounds at thermal equilibrium. However, as soon as the pre-polarized 13C-labeled compound leaves the polarizer, its hyperpolarized state would irreversibly decay to the thermal equilibrium with a decay constant characterized by T1, which is typically less than one minute. The rapid loss of nonrenewable polarization brings challenges in hyperpolarized 13C magnetic resonance imaging. This dissertation presents improved acquisition methods for hyperpolarized 13C imaging with the injection of hyperpolarized [1-13C]pyruvate, which is the most widely studied substrate to date. The improved acquisition methods include a regional bolus tracking sequence for automatic acquisition timing, real-time calibration of frequency and RF power for more robust acquisitions, metabolite specific balanced steady state free precession (bSSFP) sequence and metabolite specific fast spin echo sequence for efficient use of polarization in hyperpolarized [1-13C] imaging. The proposed acquisition methods have been demonstrated in various clinical applications on a MR 3T scanner. Bolus tracking and real-time acquisition methods have been used in imaging human brain, heart, kidney and prostate. Metabolite specific bSSFP sequence has been applied in imaging human kidney. Metabolite specific fast spin echo sequence has been demonstrated in imaging human brain.