Sub‐second proton imaging of 13 C hyperpolarized contrast agents in water

Indirect proton detection of 13 C hyperpolarized contrast agents potentially enables greater sensitivity. Presented here is a study of sub‐second projection imaging of hyperpolarized 13 C contrast agent addressing the obstacle posed by water suppression for indirect detection in vivo . Sodium acetate phantoms were used to develop and test water suppression and sub‐second imaging with frequency‐selective RF pulses using spectroscopic and imaging indirect proton detection. A 9.8 m m aqueous solution of 13 C PHIP hyperpolarized 2‐hydroxyethyl‐ 13 C‐propionate‐ d 2,3,3 (HEP), <P >  ~25% was used for demonstration of indirect proton sub‐second imaging detection. Balanced 2D FSSFP (fast steady‐state free precession) allowed the recording of proton images with a field of view of 64 × 64 mm 2 and spatial resolution 2 × 2 mm 2 with total acquisition time of less than 0.2 s. In thermally polarized sodium 1‐ 13 C‐acetate, 13 C to 1 H polarization transfer efficiency of 45.1% of the theoretically predicted values was observed in imaging detection corresponding to an 11‐fold overall sensitivity improvement compared with direct 13 C FSSFP imaging. 13 C to 1 H polarization transfer efficiency of 27% was observed in imaging detection, corresponding to a 3.25‐fold sensitivity improvement compared with direct 13 C FSSFP imaging with hyperpolarized HEP. The range of potential applications and limitations of this sub‐second and ultra‐sensitive imaging approach are discussed. Copyright © 2014 John Wiley & Sons, Ltd.