Raw Arterial Spin Labeling Data Can Help Identify Arterial Occlusion in Acute Ischemic Stroke

Brain perfusion magnetic resonance imaging using pseudocontinuous arterial spin labeling in 314 dogs and cats

Background

Arterial spin labeling (ASL) is a noninvasive brain perfusion magnetic resonance imaging (MRI) technique that has not been assessed in clinical veterinary medicine.

Hypothesis/Objectives

To test the feasibility of ASL using a 1.5 Tesla scanner and provide recommendations for optimal quantification of cerebral blood flow (CBF) in dogs and cats.

Animals

Three hundred fourteen prospectively selected client‐owned dogs and cats.

Methods

Each animal underwent brain MRI including morphological sequences and ≥1 ASL sequences using different sites of blood labeling and postlabeling delays (PLD). Calculated ASL success rates were compared. The CBF was quantified in animals that had morphologically normal brain MRI results and parameters of ASL optimization were investigated.

Results

Arterial spin labeling was easily implemented with an overall success rate of 95% in animals with normal brain MRI. Technical recommendations included (a) positioning of the imaging slab at the foramen magnum and (b) selected PLD of 1025 ms in cats and dogs <7 kg, 1525 ms in dogs 7 to 38 kg, and 2025 ms in dogs >38 kg. In 37 dogs, median optimal CBF in the cortex and thalamic nuclei were 114 and 95 mL/100 g/min, respectively. In 28 cats, median CBF in the cortex and thalamic nuclei were 113 and 114 mL/100 g/min, respectively.

Conclusions and Clinical Importance

Our survey of brain perfusion ASL‐MRI demonstrated the feasibility of ASL at 1.5 Tesla, suggested technical recommendations and provided CBF values that should be helpful in the characterization of various brain diseases in dogs and cats.

Regional Arterial Spin Labeling Perfusion Defect Is Associated With Early Ischemic Recurrence in Patients With a Transient Ischemic Attack

Background and Purpose- With the lack of confirmatory examinations, the distinction of a transient ischemic attack (TIA) from various TIA-mimicking diseases is difficult, particularly in diffusion-weighted imaging (DWI)-negative TIAs. In this study, we aimed to evaluate the relationship between arterial spin labeling (ASL) perfusion defects and early ischemic recurrence (FU-DWI [+]) in patients with DWI-negative TIAs. Methods- We assessed consecutive patients with a DWI-negative TIA within 24 hours of symptom onset, who underwent both ASL images and follow-up magnetic resonance imaging during the acute period. As markers of the ASL images, we evaluated the ASL perfusion defects in each hemisphere. Arterial transit artifact (ATA) and intraarterial high-intensity signal (IAS) were also rated as markers of collateral status and blood stagnation due to large vessel occlusion, respectively. Results- Among the 136 patients with a DWI-negative TIA, 33 patients had FU-DWI (+) lesions in 36 hemispheres. In the multivariable analysis, ASL defects remained an independent predictor of FU-DWI (+) (adjusted odds ratio, 13.94 [95% CI, 5.77-33.70], P<0.001). In the evaluation of the interactive relationship between ASL defects and ATA/IAS, the (ASL [+] ATA [-]) group showed the highest frequencies of FU-DWI (+) events (55.6%) with the highest adjusted odds ratio values (adjusted odds ratio, 14.86 [95% CI, 5.63-39.24], P<0.001), indicating a negative synergistic effect between the ASL defects and ATA. Meanwhile, the (ASL [+] IAS [+]) group showed higher frequencies of FU-DWI (+) and higher adjusted odds ratio values than those of the (ASL [+] IAS [-]) and (ASL [-] IAS [-]) groups, indicating a positive synergistic effect. Conclusions- We demonstrated that ASL perfusion defects were associated with ipsilateral FU-DWI (+) in patients with a DWI-negative TIA. Furthermore, this association was enhanced with IASs and attenuated with ATAs.

ASL and susceptibility-weighted imaging contribution to the management of acute ischaemic stroke

Abstract

Magnetic resonance imaging (MRI) plays a central role in the early diagnosis of cerebral vascular events. Today, MRI is used not only for the detection of acute ischaemic lesions, but also to fine tune the diagnosis and improve patient selection for early therapeutic decision-making. In this perspective, new tools such as arterial spin labelling (ASL) and susceptibility-weighted imaging (SWI) sequences have been developed. These MRI sequences enable noninvasive assessment of brain damage, providing important diagnostic and prognostic information: evaluation of cerebral parenchymal perfusion; detection and aetiological assessment of thrombi; ruling out differential diagnoses. After a brief recall of the fundamental basis of these sequences, this article proposes an update on their current contribution to the early management of stroke victims.

Teaching Points

• These noninvasive sequences provide essential information for early management of acute stroke.

• They can detect zones of parenchymal hypoperfusion.

• Susceptibility-weighted sequences provide information on thrombus localisation and composition.

• ASL can identify certain aetiologies of stroke mimics.

• Post-therapeutic ASL perfusion status predicts outcome.

Role of atherosclerosis, clot extent, and penumbra volume in headache during ischemic stroke

OBJECTIVE

To investigate the role of large vessel atherosclerosis, blood clot extent, and penumbra volume in relation to headache in ischemic stroke patients.

METHODS

In this cross-sectional study, we performed noncontrast CT, CT angiography (CTA), and CT perfusion (CTP) in 284 participants from the Dutch Acute Stroke Study and Leiden Stroke Cohort within 9 hours after ischemic stroke onset. We collected headache characteristics prospectively using a semi-structured questionnaire. Atherosclerosis was assessed by evaluating presence of plaques in extracranial and intracranial vessels and by quantifying intracranial carotid artery calcifications. Clot extent was estimated by the clot burden score on CTA and penumbra volume by CTP. We calculated risk ratios (RRs) with adjustments (aRR) for possible confounders using multivariable Poisson regression.

RESULTS

Headache during stroke was reported in 109/284 (38%) participants. Headache was less prevalent in patients with than in patients without atherosclerosis in the extracranial anterior circulation (35% vs 48%; RR 0.72; 95% confidence interval [CI] 0.54-0.97). Atherosclerosis in the intracranial arteries was also associated with less headache, but this association was not statistically significant. Penumbra volume (aRR 1.08; 95% CI 0.63-1.85) and clot extent (aRR 1.02; 95% CI 0.86-1.20) were not related with headache.

CONCLUSIONS

Headache in the early phase of ischemic stroke tends to occur less often in patients with atherosclerosis than in patients without atherosclerosis in the large cerebral arteries. This finding lends support to the hypothesis that vessel wall elasticity is a necessary contributing factor in the occurrence of headache during acute ischemic stroke.