Magnetic Resonance Imaging Evaluation of Pulmonary Vascular Malformations: Methods
The PC cine pulse sequence incorporated an effective TR of 44 to 64 ms, ТЕ of 7 to 17 ms, flip angle of 30°, and respiratory compensation. These PC cine sequences provided 16 images per cardiac cycle and were 5 to 10 mm thick in the axial and/or coronal planes. The velocity ranges of the PC cine sequences were set at 25 to 100 cm/s. The PC cine sequences were velocity encoded in all directions (right-left, anterior-posterior, superior-inferior) for each lesion evaluated. The PC cine sequences were performed through areas of potential PVM. All of these imaging sequences utilized a 256X128 matrix and two excitations. The GRE cine and PC cine sequences were reviewed in a loop playback. natural asthma treatment
Twelve patients who had MR scans and pulmonary angiography to evaluate for central pulmonary embolus served as controls. None of these patients were suspected of having a PVM a priori.
Four patients had pulmonary angiography performed by a thoracic radiologist experienced in pulmonary arteriography (J.M.S. or P.J.J.) within 2 days after the MRI study. We used the following MRI criteria to diagnose PVM: (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 detected on the PC cine sequences using relatively low velocity ranges.
Two of us (J.M.S. and P.J.J.) independently reviewed all imaging modalities for each case (chest radiograph, CT, MRI) prior to performing and interpreting the pulmonary angiogram in those patients who had pulmonary arteriography. None of the 12 control patients had evidence of a PVM by MRI or pulmonary angiography.
Of the 11 patients in this study, 6 had all three separate MRI sequences, namely, gated spin-echo, GRE cine, and PC cine sequences. The sizes of the PVMs in this study ranged from 1 to 6 cm. These abnormalities showed flow void or intermediate gray signal on the spin-echo sequences, bright signal on GRE cine sequences, and bright signal consistent with flow on the PC cine sequences.