Magnetic Resonance Imaging Evaluation of Pulmonary Vascular Malformations: Comment
We incorporated 2-D PC cine sequences because of the potential pitfalls with cine GRE sequences and because of previous reports of MRI of PVM using PC cine sequences.-‘ We chose to use relatively low velocity ranges, as we wanted to be maximally sensitive to flowing blood; small areas of aliasing secondary to blood flowing faster than the chosen velocity range were acceptable since quantitative data were not being sought and sensitivity to fast flow remained. Also, mucus, atelectasis, and thrombus are not bright on PC cine sequences (Fig 3), and this allows distinction between these abnormalities and PVM. These PC cine sequences must be encoded in all directions (right-left, anterior-posterior, and superior-inferior) to detect any blood flow within the lesion. canadian health & care mall
Therefore, spin-echo images by themselves do not evaluate PVMs adequately because these depict a PVM as an area of flow void (black signal) on a background of black signal (air in lung tissue). The GRE cine images can yield a false-positive diagnosis of a PVM because of bright signal from mucus or various stages of thrombus. As GRE cine techniques rely on the in flow of fresh spins (moving fluid), it may miss a small PVM or PVM with very slow flow. Contrarily, PC cine techniques rely on phase shifts induced by moving spins, either in plane or through plane, to distinguish stationary tissue (no flow and thus no signal) from flowing blood. Hence, PC techniques are the most accurate MRI sequence to evaluate PVMs.
In conclusion, we have demonstrated that MRI is potentially an accurate, clinically efficacious, noninvasive imaging modality to depict PVM using these criteria: (1) flow void or intermediate gray signal on spin-echo sequences; (2) bright signal on GRE cine sequences; and (3) bright signal consistent with flow on PC cine sequences with relatively low velocity ranges. The PC cine sequence is the most accurate of all of these MRI sequences to determine if a lesion is a PVM. Although there were no pulmonary artery aneurysms or varices in our study population, we believe these MRI criteria are valid for all PVMs.