Estimation and visualization of regional and global pulmonary perfusion with 3D magnetic resonance angiography.

The purposes of this work were to estimate regional and global pulmonary perfusion and display pulmonary vasculature in 10 postoperative lung transplant patients using breath-hold, contrast-enhanced (0.2 mmol/kg, Gd DTPA-BMA, Omniscan, Nycomed, Inc., Princeton, NJ), three-dimensional (3D) magnetic resonance angiography (MRA) with specially designed double-variable-angle uniform signal excitation (VUSE) radio frequency (RF) pulses. Double-VUSE scans imaged both lungs simultaneously during contrast agent injection and provided both qualitative and quantitative information about pulmonary perfusion. Double-VUSE pulses clearly displayed healthy and diseased vessels. There was a strong correlation between contrast-enhanced double-VUSE MRA flow estimates and those measured from nuclear scans for global or whole lung (R(2) = 0.95; P = 0.000002) and upper, central, and lower thirds of the lung (R(2) = 0.89, 0.92, and 0.86, respectively; P < 0.001 for each region). In conclusion, 3D MRA using VUSE pulses in combination with a contrast agent is a valuable tool for the assessment of pulmonary perfusion that simultaneously acquires data for both the qualitative display of pulmonary vessels and the quantification of regional and global differential pulmonary blood flow.

Evaluation of radiofrequency pulses and contrast agent doses for use in 3D pulmonary magnetic resonance angiography.

Ten healthy volunteers were imaged with breath-hold, three-dimensional (3D) time-of-flight (TOF) magnetic resonance angiography (MRA) using single-variable-angle uniform signal excitation (VUSE), double-VUSE, and flat radiofrequency (RF) pulses with various doses of contrast agent. The ability of each technique to display pulmonary vasculature was evaluated. Images were segmented to isolate lungs, and maximum intensity projections (MIPs) were computed. All MIPs were assigned an image quality (IQ) rating, and signal-to-noise ratios (SNRs) were measured in pulmonary vessels. Without contrast agent, subsegmental vessels were displayed in single- and double-VUSE images while no vessels were visible in flat images. With equal doses of contrast agent, SNRs and IQ ratings were comparable for images obtained with VUSE and flat pulses. In addition, single-VUSE pulses produced more uniform signal from vessels than flat pulses in contrast-enhanced images. The results indicate that non-contrast-enhanced 3D TOF pulmonary MRA with VUSE RF pulses may be a useful screening tool. In addition, contrast-enhanced 3D TOF MRA with VUSE pulses may be useful as a stand-alone technique for assessing the pulmonary vasculature or as an adjunct to contrast-enhanced 3D TOF MRA with flat pulses. J. Magn. Reson. Imaging 10:929-938, 1999.