Abstract Purpose: To optimize a 100 msec pulse for producing CEST MRI contrast and evaluate in mice. Methods: A gradient ascent algorithm was employed to generate a family of 100 point, 100 msec pulses for use in CEST pulse trains. Gradient ascent optimizations were performed for exchange rates = 500 s-1, 1,500 s-1, 2,500 s-1, 3,500 s-1 and 4,500 s-1 and offsets = 9.6, 7.8, 4.2 and 2.0 ppm.