INTRAVASCULAR CONTRAST AGENT IMPROVES MAGNETIC-RESONANCE ANGIOGRAPHY OF CAROTID ARTERIES IN MINIPIGS

This study was designed to optimize three-dimensional (3D) time-of-nig ht (TOF) magnetic resonance angiography (MRA) sequences and to determi ne whether contrast-enhanced MRA could improve the accuracy of lumen d efinition in stenosed carotid arteries of minipigs, 3D TOF MRA was acq uired with use of either an intravascular (n = 13) and/or an extravasc ular contrast agent (n = 5) administrated at 2 to 4 weeks after balloo n-induced injury to a carotid artery in 16 minipigs. Vascular contrast , defined as signal intensity differences between blood vessels and mu scle normalized to the signal intensity of muscle, was compared before and after the injection of each contrast agent and between the two ag ents. Different vascular patencies were observed among the animals, in cluding completely occluded vessels (n = 5), stenotic vessels (n = 3), and vessels with no visible stenosis (n = 8), Superior vascular contr ast improvement was observed for small arteries and veins and for larg e veins with the intravascular contrast agent when compared with the e xtravascular contrast agent. In addition, preliminary studies in two o f the animals showed a good correlation for the extent of luminal sten osis defined by digital subtraction angiography compared with MRA obta ined after administration of the intravascular contrast agent (R2 =.71 , with a slope of.96 +/- .04 by a linear regression analysis). We conc luded that use of an intravascular contrast agent optimizes 3D TOF MRA and may improve its accuracy compared with digital subtraction angiog raphy.