Magnetic Resonance Imaging Evaluation of Pulmonary Vascular Malformations
Pulmonary vascular malformations (PVMs) may be A congenital or acquired, singular or multiple, and include arteriovenous malformations (AVMs), arteriovenous fistulas, aneurysms, and varices. The finding of a smooth, noncalcified pulmonary nodule/ mass with feeding and/or draining vessels on a chest radiograph or computed tomographic (CT) scan suggests a PVM. Traditionally, these lesions have been confirmed diagnostically with pulmonary angiography. in detail
Contrast-enhanced CT has been occasionally used to diagnose PVM, though false-positive cases exist. More recently, magnetic resonance imaging (MRI) has been reported to identify these abnormalities.’ Various MRI pulse sequences have been used to identify PVM. Cardiac gated and respiratory compensated relatively short repetition time (TR) and echo delay (ТЕ) spin-echo sequences typically show a flow void within the vascular malformation because of the relatively rapidly flowing blood, though regions of intermediate gray signal may be seen because of relatively slow-flowing blood. Of course, the lack of signal intensity within the lesion may make it hard to detect the abnormality when it is surrounded by normal lung with its minimal or no signal intensity.
In general, the lungs are difficult to image with MRI because of susceptibility artifacts. Previous reports show the advantage of adding “flow sensitive” gradient-recalled echo (GRE) sequences to the MRI evaluation of PVM;’ these GRE sequences include single-slice breath-held acquisitions as well as cine sequences. The cine images permit review of the data in a closed-loop playback. More recently, phase contrast (PC) cine sequences have been developed that allow imaging of PVM and quantification of blood flow. The purpose of this study was to establish MRI criteria for the diagnosis of PVM.