Enhancement of Endogenous CEST Effects by Optimizing Pre-Saturation Pulse Train Properties

Moritz Zaiss¹, Benjamin Schmitt¹, Peter Bachert¹

Endogenous chemical exchange saturation transfer effects of labile protons localized in small metabolites like amide protons or hydroxyl groups have a small spectral distance from bulk water protons. Therefore, transfer effects are overlapped by the direct water saturation effect, the so called spillover effect, which is eliminated by asymmetry analysis. Short saturation times and duty cycles due to clinical restrictions also distort acquired z-spectra. In this work, these distortions are examined by numerical simulations and phantom studies which lead to an unexpected optimum of the z-spectrum asymmetry for small pulse durations of few ms lowering the pulsed spillover effect.