Arterial spin labeling perfusion MRI in pediatric arterial ischemic stroke: initial experiences

Abstract

Purpose: To investigate the feasibility and utility of arterial spin labeling (ASL) perfusion MRI for characterizing alterations of cerebral blood flow (CBF) in pediatric patients with arterial ischemic stroke (AIS).

Materials and methods: Ten children with AIS were studied within 4 to 125 hours following symptom onset, using a pulsed ASL (PASL) protocol attached to clinically indicated MR examinations. The interhemisphere perfusion deficit (IHPD) was measured in predetermined vascular territories and infarct regions of restricted diffusion, which were compared with the degree of arterial stenosis and volumes of ischemic infarcts.

Results: Interpretable CBF maps were obtained in all 10 patients, showing simple lesion in nine patients (five hypoperfusion, two hyperperfusion, and two normal perfusion) and complex lesions in one patient. Both acute and follow-up infarct volumes were significantly larger in cases with hypoperfusion than in either hyper- or normal perfusion cases. The IHPD was found to correlate with the degree of stenosis, diffusion lesion, and follow-up T(2) infarct volumes. Mismatch between perfusion and diffusion lesions was observed. Brain regions presenting delayed arterial transit effects were tentatively associated with positive outcome.

Conclusion: This study demonstrates the clinical utility of ASL in the neuroimaging diagnosis of pediatric AIS.

Figure 1

The inter-hemisphere perfusion deficit (IHPD) measured in ROIs of diffusion lesions and vascular territories (VT). Data are presented from the shortest to the longest imaging time following symptom onset in the 11 lesions. Each lesion is represented by a pair of bars, the red one for vascular territory, and green one for ROI. The positive and negative 20% lines are shown. Patient number is shown in the bracket.

Figure 2

CBF, DWI, initial and follow-up T₂ images, and MRA for 5 hypoperfusion cases. Infarct lesions are marked by green arrows, arterial transit effects are marked by blue arrows, arterial stenosis is marked by yellow arrows. For Patient #8, secondary left frontal lobe infarct was marked by a rose arrow.

Figure 3

CBF, DWI, and initial T₂ images of a representative patient (#6) with PWI>DWI lesion (A), and another representative patient (#8) with PWI<DWI lesion. Regions of PWI lesion, DWI lesion and conjunction of PWI and DWI lesions are indicated by green, red and blue colors respectively, which are overlaid upon T₂ images.

Figure 4

CBF, DWI, initial and follow-up T₂ images, and MRA for 2 hyperperfusion (Patient #2 and #10) and 2 normal perfusion (Patient #4 and #5) cases. In Patient #2, CBF map shows delayed arterial transit in the left MCA territory (blue arrow). In Patient #10, CBF map shows hyperperfusion in the left thalamic region, and a corresponding lesion is present on both DWI and initial T₂-weighted images. In Patient #4, CBF map shows hypoperfusion with delayed transit (blue arrow) in the left MCA territory. In Patient #5, CBF map shows normal perfusion, despite a small ischemic lesion in DWI, T₂ and follow-up T₂ images. Stenosis is present in M1 segment of Patient #2, #4 and #5 on MRA (yellow arrows).

Figure 5

CBF, DWI, initial and follow-up T₂ images, and MRA for the complex infarct case. The hypoperfusion lesions locate in the left and right MCA territories, perfusion deficit is consistent with diffusion restricted lesion and T₂ hyperintensity (green arrows). The hyperperfusion lesions locate in the right PCA and left ACA territories (blue arrows), where there is restricted diffusion and mildly abnormal T₂ signal. MRA shows left ICA is small and left MCA is absent and right PCA stenosis (yellow arrows).