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Abstract #4361

Optimization of saturation frequency offset step size for CEST asymmetry contrast  of human brain at 7T MRI

Ayan Debnath1,2, Hari Hariharan2, Ravi Prakash Reddy Nanga2, Puneet Bagga2, Dinil Sasi1, Ravinder Reddy2, and Anup Singh1,3

1Center for Biomedical Engineering, Indian Institute of Technology Delhi, New Delhi, India, 2Center for Magnetic Resonance & Optical Imaging, University of Pennsylvania, Philadelphia, PA, United States, 3All India Institute of Medical Science, New Delhi, India

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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