Using healthy volunteers to optimize amide proton transfer CEST sequences.

Optimising CEST sequences for clinical use is difficult due to the lack of representative phantoms. Healthy volunteers do not show the variation in pH or concentration that these sequences seek to detect. However, in this work we show how the inherent T₁ sensitivity of CEST sequences [1] can be exploited to optimise them in healthy volunteers. We demonstrate that the sequence conditions that maximise the grey/white matter contrast in exchange maps are also the parameter conditions that maximise the exchange sensitivity. This method provides an effective way to optimise in vivo CEST sequences without the need for phantoms or simulations.