Amide Proton Transfer Imaging with Continuous Wave Dual Frequency Saturation Can Detect the Amide Proton Peak in the Z-Spectrum Acquired at 3T

Rachel Scheidegger^1,2, Elena Vinogradov^1,3, Weiying Dai^1,3, David C. Alsop^1,3

We present a chemical exchange saturation transfer (CEST) imaging sequence with continuous wave saturation preparation relying on a 3-way subtraction between label frequency, control frequency, and simultaneous dual frequency RF irradiation to remove B0 inhomogeneity and intrinsic magnetization transfer (MT ) from in-vivo images. We demonstrate this approach yields amide proton transfer (APT) images free of susceptibility artifacts and MT asymmetry, without any additional B0 correction. This allows clear and robust measurement of the amide proton peak in the z-spectrum acquired at 3T. This new method may improve the feasibility of quantifying exchange rates in-vivo and measuring pH.