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AJNR - American Journal of Neuroradiology

Published ahead of print on March 27, 2008
doi: 10.3174/ajnr.A1030

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Arterial Spin-Labeling in Routine Clinical Practice, Part 1: Technique and Artifacts

A.R. Deibler^a, J.M. Pollock^a, R.A. Kraft^b, H. Tan^b, J.H. Burdette^a and J.A. Maldjian^a

^a Department of Radiology, Wake Forest University School of Medicine, Winston-Salem, NC
^b Department of Biomedical Engineering, Wake Forest University School of Medicine, Winston-Salem, NC

View larger version (37K): [in this window] [in a new window]   Fig 1. Normal ASL CBF map. Multisection JPEG map with color ramp representing units of mL/100 g tissue/min. No flow asymmetry or artifact is present.

View larger version (68K): [in this window] [in a new window]   Fig 2. Robust CBF in a pediatric patient, an 8-year-old boy with elevated CBF values in gray and white matter, a normal finding in this age group. CBF has been reported to peak around 8 years of age before gradually decreasing to normal adult levels.

View larger version (53K): [in this window] [in a new window]   Fig 3. Physiologic regional distribution of spin tag. Hyperfrontal (white arrows) and visual cortex (yellow arrow) patterns of signal intensity, normal variants on ASL CBF maps.

View larger version (38K): [in this window] [in a new window]   Fig 4. Effect of spin tag decay during image acquisition. ASL CBF map shows decreased global signal intensity in the more rostral images compared with more inferior levels. Images are acquired from inferior to superior.

View larger version (46K): [in this window] [in a new window]   Fig 5. Tissue masking artifact. Postgadolinium T1-weighted image reveals a tangle of enhancing vessels in the right posterior thalamic region consistent with arteriovenous malformation (yellow arrow). The lesion is markedly hyperperfused on the ASL CBF map, but a central signal intensity void is seen because of tissue-masking error (white arrow). Corresponding unmasked image confirms the source of the artifact.

View larger version (54K): [in this window] [in a new window]   Fig 6. Transit time effects. Axial T2-weighted image through the cavernous sinuses revealed absence of flow void in the right internal carotid artery (not shown), indicating slow flow or occlusion. Restricted diffusion is present, which is consistent with watershed infarct (arrow). ASL CBF map reveals decreased flow in the right posterior watershed zone as well as linear high signal intensity representing slow flow in cortical vessels (arrowheads).

View larger version (40K): [in this window] [in a new window]   Fig 7. Susceptibility artifact in a 5-year-old boy with previous resection of a glioma. Focally decreased signal intensity is present in the right parietotemporal region on the ASL CBF maps (arrow). The baseline magnetization map confirms the presence of metallic hardware causing magnetic field distortion (arrow).

View larger version (42K): [in this window] [in a new window]   Fig 8. Globally increased ASL signal intensity due to artifact. Perfusion pattern appears normal except for high signal intensity in the lateral ventricles (arrows), due to shinethrough of T2-weighted signal intensity that was not adequately suppressed during only 1 volume (vol 10). Vol 11 represents a normal control-label image subtraction obtained during signal intensity averaging.

View larger version (72K): [in this window] [in a new window]   Fig 9. Artifact secondary to motion. A peripheral ring of high signal intensity is a common finding in ASL cases degraded by motion (arrow).

View larger version (33K): [in this window] [in a new window]   Fig 10. Artifact secondary to asymmetric coil sensitivity. There is a regional zone of high perfusion signal intensity in the right cerebral hemisphere that corresponds to the same zone of high signal intensity on the diffusion image and the M0.