Good resolution of contrast-enhanced MRA using USPIO on coronal plane acquisition: experimental evaluation of time-of-flight effect using flow phantom and animal study.

Abstract

The major disadvantage of 3D TOF MRA is the saturation effect (1-4), even in 3D acquisition. The orientation of the blood vessel to the slice plane is crucial for magnetic resonance angiography. When flowing spins travel parallel to imaging plane, they receive many RF pulses, which decreases the signal (5-7). This is the saturation effect. Maximum enhancement occurs when blood flow is perpendicular to the imaging plane and near the imaging plane that receives the minimum number of RF pulses. When imaging the abdominal aorta and lower extremities, this method requires scanning the long imaging segment of vessels using axial plane and results in a prolonged study time (3,8-12). Recently, scans were obtained parallel to flow after the dynamic gadolinium injection (9,13), which resulted in good images in many areas. But it is not known how flow enhi~ncement effects contributed to the contrast-enhanced MR angiography. We have developed a new contrast agent, AMI-227, which has long blood half-life, so the change of the concentration can be ignored. Using this contrast agent, we directly compare the 3D TOF MRA scanning results obtained in both axial and coronal sections.