ScholarWorks@성균관대학교

초록

Purpose CEST at ultra-high fields such as 15.2 T benefits significantly from increased signal and increased spectral resolution. However, inhomogeneous fields become a confounding issue for B0 and B1. While B0 inhomogeneity correction is widely studied and implemented, methods for B1 correction have been limited to interpolation, which requires close to ground truth sampling across B1 or sophisticated methods that increase data acquisition requirements. This work demonstrates a simple and easy-to-employ model-based linearization that allows for reasonable B1 correction with as low as two B1 samples for implementation.Methods Simulation and in vivo rodent brain CEST data at 15.2 T were tested for reasonable B1 correction using a surface coil to demonstrate an exaggerated situation of B1 inhomogeneity. Individual exchange fitting was performed, and quantified maps were examined for apparent residual B1 dependencies, and quantitative values were examined for consistency across animals.Results Simulation showed linearization significantly improved linear dependency over simple linear interpolation, even when multiple pools were involved. B1 corrected Z-spectra demonstrated reasonable consistency across animals, and parameter maps of simple quantifying CEST parameters demonstrated little B1 dependency. Fitting CEST curves demonstrates similar consistency and independence from B1. Finally, comparison of parameters across animals demonstrates reasonable consistency after B1 correction.Conclusion The simple linearization described in this paper offers a facile way to rapidly correct for B1 inhomogeneity with minimally required additional spectral sampling. This method can have significant advantages, particularly in scan-time restricted situations where multiple Z-spectra at more than two power levels are not feasible.

키워드