iDQC MRI weighted by longitudinal relaxation in the rotating frame

Abstract

A long-duration, low-power, off-resonance spin-locking pulse was incorporated into the COSY revamped by asymmetric z gradient-echo detection (CRAZED) pulse sequence in order to evaluate the effects of intermolecular double-quantum longitudinal relaxation in the tilted rotating frame (T-1p,DQ(eff)). This modified CRAZED sequence was followed by a standard fast spin-echo imaging sequence to form images with T-1p,DQ(eff)-weighted contrast. Imaging experiments were performed on an agarose-gel phantom and mouse-tail tissue at 600 MHz. Experimental results demonstrated the feasibility of imaging applications based on T-1p,DQ(eff) as a novel contrast mechanism, and showed that iDQC off-resonance longitudinal relaxation in the rotating frame T-1p,DQ(eff) is sensitive to the tilt angle theta and the effective spin-locking field omega(e). Imaging based on T-1p,DQ(eff) has reduced RF power deposition compared to on-resonance spin-locking, which is advantageous for human applications.