31P-CEST “matrix” for in vivo rat brain: novel apparent Z spectra analysis towards sensitive imaging

Motivation: There was a lack of systemic CEST-type experiments and further analysis for 31P-MRS, towards detailed interaction quantification and novel sensitive detection scheme. Goal(s): Through a comprehensive 31P-CEST "matrix" study, to explore an accelerated 31P-CEST scheme for sensitive imaging. Approach: 31P-CEST experiments were performed on in vivo rat brain at 9.4T, with novel apparent Z spectra calculated using PCr, Pi, PME, and α/β/Γ-ATP respectively. Results: These apparent Z spectra not only clearly indicated the interactions among 31P metabolites, but also suggested that signal amplification and acquisition acceleration could be achieved for individual metabolites (~several mM) by indirectly detecting the bulk 31P signal (~20 mM). Impact: This study demonstrates that 31P-CEST technique enables the detection of individual metabolites (several mM) by indirectly detecting the bulk 31P signal (~20 mM), indicating the potential of 31P-CEST-MRI for accelerating acquisition and enhancing sensitivity by removing the spectral dimension.