2D Constant Time Correlated Spectroscopy (CT-COSY): Simulated and Experimental Results

Magnetic Resonance Spectroscopy (MRS) allows noninvasive measurements of the relative concentrations of metabolites in the human organs such as brain, breast and prostate. Spectral assignments can be ambiguous in one-dimensional (ID) MRS due to signal overlap. Two-dimensional (2D) correlated spectroscopy (COSY) improves spectral peak separation of J-coupled resonances by spreading the signals into a plane. Constant lime correlated spectroscopy (CT-COSY) can considerably improve the SNR of cross peaks using chemical shift encoding by shifting the position of a refocusing 180degrees pulse within a constant lime (T-c). A spatially resolved CT-COSY sequence has been implemented and optimized on a whole body 1.5T MRI/MRS scanner. Dependence of 2D cross peaks on Tc was investigated using GAMMA simulated spectra and experimentally verified using phantom solutions of several metabolites. Compared to a basic COSY spectrum, a broadband homonuclear proton-proton decoupling was achieved in the second spectral dimension of CT-COSY.