Chemical-exchange-saturation-transfer(CEST) MRI is being used for mapping molecular-information. CEST contrasts such as Creatine-weighted(frequency-offset=2ppm), Glutamate-weighted(frequency-offset=2ppm) and APT-weighted(frequency-offset=3.5ppm) are being explored for potential clinical applications. Computation of contrast(CEST-asymmetry) at a frequency-offset require data acquisition at multiple offset-frequencies either for B0-inhomogenity correction or generating z-spectra. Objective of this study was to evaluate the effect of sampling frequency-offset step-size (0.1, 0.2, 0.3, 0.4, 0.5ppm) on CEST-asymmetry contrast. Standard-deviation, coefficient-of-variation and normalized-mean-sum-squared-errors(nMSSE) increases while correlation decreases with increase in step-size. By considering both scan time and error, step-size of 0.2 to 0.3 is optimum for computing CESTasym.
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