Hyperpolarized 13C MR angiography using trueFISP.

A (13)C-enriched water-soluble compound (bis-1,1-(hydroxymethyl)-1-(13)C-cyclopropane-D(8)), with a (13)C-concentration of approximately 200 mM, was hyperpolarized to approximately 15% using dynamic nuclear polarization, and then used as a contrast medium (CM) for contrast-enhanced magnetic resonance angiography (CE-MRA). The long relaxation times (in vitro: T(1) approximately 82 s, T(2) approximately 18 s; in vivo: T(1) approximately 38 s, T(2) approximately 1.3 s) are ideal for steady-state free precession (SSFP) imaging with a true fast imaging and steady precession (trueFISP) pulse sequence. It was shown both theoretically and experimentally that the optimal flip angle was 180 degrees. CE-MRA was performed in four anesthetized live rats after intravenous injection of 3 ml CM. The angiograms covered the thoracic/abdominal region in two of the animals, and the head-neck region in the other two. Fifteen consecutive images were acquired in each experiment, with a flip-back pulse at the end of each image acquisition. In the angiograms, the vena cava (SNR approximately 240), aorta, renal arteries, carotid arteries (SNR approximately 75), jugular veins, and several other vessels were visible. The SNR in the cardiac region was 500. Magnetization was preserved from one image acquisition to the next using the flip-back technique (SNR(cardiac) approximately 10 in the 15th image).