MRA STUDIES OF ARTERIAL-STENOSIS - IMPROVEMENTS BY DIASTOLIC ACQUISITION

Cardiac-phase-specific data acquisition is used to reduce signal loss in MR Angiography resulting from disturbed flow. RF pulses are deliver ed continuously throughout the cardiac cycle, but incrementation of ph ase-encoding gradients and data storage are enabled only during the ch osen part of the cycle. Studies in a stenotic pulsatile flow phantom d emonstrate that poststenotic signal loss is primarily determined by th e mean flow velocity, and is not appreciably affected by acceleration or deceleration of the mean flow rate. The signal loss is least in dia stole. In vivo studies in patients with carotid artery disease show th at data acquisition in diastole reduces the apparent degree and extent of carotid bifurcation stenosis and provides a crisper definition of the vascular lumen. The additional time required for cardiac-phase-spe cific acquisition can be reduced by gating only the lower-order phase- encoding lines while retaining acceptable image quality.