Investigating the Feasibility of In Vivo Perfusion Imaging Methods for Spinal Cord Using Hyperpolarized [C]t-Butanol and [C,N]Urea.

PURPOSE

This study examined the feasibility of using two novel agents, hyperpolarized [C]t-butanol and [C,N]urea, for assessing in vivo perfusion of the intact spinal cord in rodents. Due to their distinct permeabilities to blood brain barrier (BBB), we hypothesized that [C]t-butanol and [C,N]urea exhibit unique C signal characteristics in the spinal cord.

PROCEDURES

Dynamic C t-butanol MRI data were acquired from healthy Long-Evans rats using a symmetric, ramp-sampled, partial-Fourier C echo-planar imaging sequence after the injection of hyperpolarized [C]t-butanol solution. In subsequent scans, dynamic C urea MRI data were acquired after the injection of hyperpolarized [C,N]urea. The SNRs of t-butanol and urea were calculated for regions corresponding to spine, supratentorial brain, and blood vessels and plotted over time. Mean peak SNR and AUC were calculated from the dynamic plots for each region and compared between t-butanol and urea.

RESULTS

In spine and supratentorial brain, the mean peak SNR and AUC of t-butanol were significantly higher than those of urea (p < 0.05). In contrast, urea was predominantly contained within vasculature and exhibited significantly higher levels of mean peak SNR and AUC compared to t-butanol in blood vessels (p < 0.05).

CONCLUSION

This study has demonstrated the feasibility of using hyperpolarized [C]t-butanol and [C,N]urea for assessing in vivo perfusion in cervical spinal cord. Due to differences in blood-brain barrier permeability, t-butanol rapidly crossed the blood-brain barrier and diffused into spine and brain tissue, while urea predominantly remained in vasculature. The results from this study suggest that this technique may provide unique non-invasive imaging tracers that are able to directly monitor hemodynamic processes in the normal and injured spinal cord.