University of Pennsylvania

Kejia Cai

Ravinder Reddy

Hari Hariharan

Mohammad Haris

Anup Singh

Feliks Kogan

Ravi Prakash Reddy Nanga

A non-invasive imaging approach using CEST and MRS may be used to monitor the cleavage of the poly-L-glutamate (PLG) backbone. The cleavage of PLG by cathespsin B can expose exchangeable &#x2014;NH2 protons in the PLG that are then monitored non-invasively through CEST. The technique can provide direct information on malignant tissue and tumor aggressiveness, and can also be used to monitor treatment.

Magnetic resonance imaging of poly-L-glutamate

An endogenous source of magnetic resonance image contrast of biological tissues is provided by modeling a conventional magnetization transfer (CMT) spectrum using z-spectral data and generating magnetization transfer ratio maps from the magnetization transfer spectrum at a frequency of interest. A contribution by the CMT spectrum from the z-spectral data is removed and a direct water saturation component is modeled using the z-spectral data with removed CMT spectrum (z-spectral). When this modeled direct water saturation component contribution is removed from the z-spectral, then the remaining z-spectra reflects new contrast due to chemical exchange saturation transfer (CEST) and magnetization transfer/exchange effect from aliphatic protons probably associated with labile proteins, peptides and lipids, named as novel magnetization transfer (NMT). This technique can be used to illustrate subtle changes in biological tissue as a result of diseases states, provide better visibility of brain white matter plaques, provide improved CEST contrast, provide better visualization of proteins, peptides, and lipids in biological tissue using NMT contrast, improve segmentation of white matter and gray matter in brain images, and the like.

Endogenous magnetization contrast in MRI

The CEST effect for various neurotransmitters and energy metabolites in the brain and muscles and various endogenous metabolites in the liver, brain, and myocardium are imaged using MR imaging to illustrate a unique CEST effect that may be used to monitor the concentration of the metabolite and hence to characterize and monitor various disease states in the body correlated to the concentration of that metabolite. By adjusting the timing, amplitude, and length of the RF pulse as well as other parameters of the CEST pulse sequence to address the unique chemical shifts and exchange rates of the target, new targets with unique characteristics may be acquired using CEST MR imaging.

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Elkins Park, PA, United States of America

Kejia Cai