MR Angiography in Sickle Cell Disease: Usefulness of Orthogonal 3D-TOF Examinations in Elimination of Artifactual Flow Gaps

We compared maximum intensity reconstructions (MIP's) of intracranial 3D-TOF MR angiograms performed in 2 orthogonal planes (axial and coronal) with MIP of MRA in the axial plane only in patients with sickle cell disease. MR imaging has revealed ischemic changes in asymptomatic patients (1). Because artifactual MRA flow gaps are recognized in areas of rapid flow turbulence (2) such as are reported in proximal middle cerebral artery (M1) segments in this disease (3), there may be a tendency to inaccurately estimate stenoses on MRA (2). Orthogonal MIP studies in this population may improve accuracy of MRA. Nineteen patients with sickle cell disease (9 asymptomatic, 10 with suspected stroke) and 6 controls were studied using 3D RF-FAST MRA in both axial and coronal planes. MIP images were viewed in rotations about the spinal axis and flow gaps observed to be present or absent in supraclinoid internal carotid arteries (ICA's) and Ml segments. Kappa statistics were used to measure degree of agreement between paired axial and orthogonal MIP images in “series”. Addition of coronal MRA changed results from positive to negative in 1 asymptomatic patient 1 control but did not change results in 10 symptomatic patients. Kappa statistics showed agreement ranging from fair to substantial. Probability of flow gaps in ICA's and Ml segments in orthogonal MIP's ranged from 0.28 to 0.40, compared with axial MIP only of 0.40 to 0.52, respectively. Our results suggest that using axial and coronal MRA's in “series” in sickle cell disease may increase specificity and positive predictive value.