High-resolution pulmonary arterio- and venography using multiple-bolus multiphase 3D-Gd-mRA.

The purpose of this study was to demonstrate selective visualization of pulmonary arteries and veins with high spatial resolution for improved detection of vascular pathologies. Time-resolved pulmonary three-dimensional gadolinium-enhanced magnetic resonance angiograms (3D-Gd-MRA) were acquired with an ultrashort 3D fast low-angle shot (FLASH) sequence (TR/TE 2.3/0.9 msec) using asymmetric k-space sampling in readout, phase-encoding, and partition directions. In a single breath-hold four consecutive acquisitions were performed with a scan time of 6.28 seconds for each phase. A spatial resolution of 1.9 x 1.4 x 2 mm(3) could be achieved for a 12 cm thick 3D volume. To exploit the intrinsic enhancement kinetics of the pulmonary vascular system, the infusion of two gadolinium chelate boli was synchronized with the acquisition of the first and third data sets. This infusion strategy created two predominantly pulmonary arterial and venous data sets with the arterial and venous signal being maximally anti-correlated in time. A further separation of arterial and venous signal could be achieved by means of a correlation analysis. Eight patients with suspected thrombi in the pulmonary veins were studied. The calculated correlation angiographies provided high-quality pulmonary arterio- and venograms. Background signal was completely eliminated, allowing maximum intensity projection analysis of the full data set. In 7/8 patients no venous contamination of the arterial phase and vice versa was found. Patency of the pulmonary arteries and veins could be reliably assessed to the level of the segmental vessels. The combination of ultrafast multiphase 3D-Gd-MRA and dual-bolus injection with a correlation analysis of vascular signal provides high-resolution pulmonary arterio- and venograms. This imaging strategy initiates a new competitor to X-ray angiography.