Cardiac Perfusion Imaging Using Hyperpolarized 13C Urea Using Flow Sensitizing Gradients

Purpose: To demonstrate the feasibility of imaging the first passage of a bolus of hyperpolarized C-13 urea through the rodent heart using flow-sensitizing gradients to reduce signal from the blood pool. Methods: A flow-sensitizing bipolar gradient was optimized to reduce the bright signal within the cardiac chambers, enabling improved contrast of the agent within the tissue capillary bed. The gradient was incorporated into a dynamic golden angle spiral C-13 imaging sequence. Healthy rats were scanned during rest (n = 3) and under adenosine stress-induced hyperemia (n = 3). Results: A two-fold increase in myocardial perfusion relative to rest was detected during adenosine stress-induced hyperemia, consistent with a myocardial perfusion reserve of two in rodents. Conclusion: The new pulse sequence was used to obtain dynamic images of the first passage of hyperpolarized C-13 urea in the rodent heart, without contamination from bright signal within the neighboring cardiac lumen. This probe of myocardial perfusion is expected to enable new hyperpolarized C-13 studies in which the cardiac metabolism/perfusion mismatch can be identified. (C) 2015 The Authors. Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance.