Magnetic resonance angiography (PVMRA) can evaluate peripheral vascular disease. Gadolinium-based MRI contrast agents are used to maximize signal- and contrast-to-noise. Contrast-enhanced MRA is an efficient means of imaging the aorta, iliac and femoral vessels. Vascular resolution is maximized when a slab is imaged in the coronal plane with good depiction of abdominal vessels in short scan times. Blood saturation in the coronal plane diminshes signal inflow. Gadolinium agents can be injected dynamically while the 3D data set is acquired in a coronal plane to enhance vascular signal. The use of blood pool agents possessing longer plasma retention times is ideal then for contrast-enhanced MRA. Two such compounds, NMP-013 and NMP-015, significantly prolong plasma retention with fewer toxicity effects compared to larger blood pool contrast agents. Methods and Results Pre- and post-contrast MR angiograms of a normal rabbit are shown for Gd-DTPA (injected at center of k-space) and NMP-015 (injected 5 minutes before image acquisition) at 0.1 mmol/kg Gd (Figure 25). Vascular signal (due to inflow) was severely reduced pre-contrast. The post-contrast vascular anatomy on the right sides below, due solely to a Ti-shortening effect, is much more striking in the NMP-015 pentamer (lower right), with improved depiction of smaller arteries and veins in the pelvic and peripheral regions over a longer period. Discussion PVMRA can be dramatically enhanced by prolonged plasma persistence of an added contrast agent. Trimer and pentamer formulations of Gd-DTPA lead to significantly greater PVMRA contrast for longer periods of time over Gd-DTPA. This effect can be advantageous in trade-off issues of the scan time, resolution, and SNR required, and of the dosage and toxicity of the agent used.
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