Variants of Me-LOVARs

We claim a Multi-echo Parametric VARiation Saturation (MePaVARS) sequence, which places multiple image readouts in between a series of saturation pulses. with the saturation pulse parameters varied which allows the generation of CEST contrast maps with patterns of signal loss encoded into the images for better discrimination between various CEST imaging agents according to these patterns produced by variation of saturation conditions. The saturation parameter changes include, but are not limited to, saturation power (B1), length (tsat), number of pulses, shape of saturation pulses, amplitude of saturation pulses, saturation offset frequency, or a combination of these variations. The sequence enabling rapid collection of CEST images is based on saturation modules, each consisting of a saturation pulse or series of pulses, a low flip-angle gradient-echo readout and may include a flip back pulse or may not, with at least two modules included in the sequence with the saturation parameters varied between successive modules. This sequence partially builds on our previous invention, PCT/US13/452,221, as systematically changing the saturation parameters (as mentioned above), creates saturation-transfer contrast patterns which depend on the chemical exchange properties of exchanging protons allowing detection and discrimination using various pattern-recognition methods. This allows improvement of the image Contrast-to-Noise Ratio, image specificity and agent quantification in vitro and in vivo.

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