Ph-weighted mri using fast amine chemical exchange saturation transfer (cest) imaging

Abstract

A pH-weighted chemical exchange saturation transfer (CEST) magnetic resonance imaging (MRI) method and system are provided that works by indirectly measuring the NMR signal from amine protons found on the backbones of amino acids and other metabolites, which resonate at a frequency of +2.8-3.2 ppm with respect to bulk water protons. The technique uses a modified magnetization transfer radiofrequency saturation pulse for the generation of image contrast. A train of three 100 ms Gaussian pulses at high amplitude (6 uT) or Sinc3 pulses are played at a particular frequency off-resonance from bulk water prior to a fast echo planar imaging (EPI) readout, with one full image acquired at each offset frequency. This non-invasive pH-weighted MRI technique does not require exogenous contrast agents and can be used in preclinical investigations and clinical monitoring in patients with malignant glioma, stroke, and other ailments.