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Improving Fidelity of Concentration Dependence in CEST- MRI using pH-insensitive Low Duty Cycle Saturation Pulse Trains
Julius Chung1 and Tao Jin1
1University of Pittsburgh, Pittsburgh, PA, United States
Conventional CEST signal is dependent on both the labile proton concentration and exchange rate. Low DC of π-pulse trains can reduce the dependence of CEST signal on the exchange rate, making it only sensitive to the labile proton concentration.
Figure 1. Simulation shows MTR asymmetry concentration dependence at 1.9 ppm 10 % duty cycle π pulses with avg. B1 = 0.48 μT (a). MTR asymmetry measured in creatine phantoms at varying pH using different duty cycles with avg. B1 = 0.48 μT (b) show increasing pH dependence with increasing duty cycle. In creatine phantoms with varying concentration and varied pH, the average Rex asymmetry with an avg. B1 = 0.97 μT using continuous wave saturation showed relatively weak linear dependence on concentration (c) while a 10% DC π pulse showed strong linear dependence on concentration (d).