Contrast-enhanced magnetic resonance angiography of the pulmonary vasculature. A review.

Magnetic resonance angiography (MRA) has been established as a powerful noninvasive imaging modality. Its applications to the study of the pulmonary vasculature have been hampered by a multitude of factors, such as respiratory and cardiac motion artifacts, saturation problems, long acquisition times, and limited spatial resolution. The recent introduction of contrast-enhanced MRA (CE-MRA) has greatly improved the potential for possible investigation of the pulmonary arteries under clinical conditions. Three-dimensional sequences with minimum TR and TE, a flip angle between 20 degrees and 60 degrees, and minimum slice thickness can be considered an optimal approach for breath-hold imaging combined with the automatic injection of contrast medium. Early studies have demonstrated the superiority of CE-MRA over nonenhanced techniques. The major indication for CE-MRA of the pulmonary vasculature is pulmonary embolism. Here a sensitivity of 85% and specificity of 95% can be obtained. It can be complemented by perfusion imaging, ventilation imaging, functional measurements of the right ventricle, and MR venography of the pelvic and femoral veins. Blood pool contrast agents will open new perspectives in the future. This article reviews the technical aspects of CE-MRA of the pulmonary vasculature, pathologic findings, and their interpretation as well as present and future clinical applications.