Multiphase arterial spin labeling imaging to predict early recurrent ischemic lesion in acute ischemic stroke

In acute ischemic stroke (AIS), the hemodynamics around the lesion are important because they determine the recurrence or prognosis of the disease. This study evaluated the effects of perfusion deficits in multiphase arterial spin labeling (ASL) and related radiological parameters on the occurrence of early recurrent ischemic lesions (ERILs) in AIS. We assessed AIS patients who underwent multiphase ASL within 24 h of symptom onset and follow-up diffusion-weighted imaging within 7 days. ASL perfusion deficit, arterial transit artifact (ATA), and intra-arterial high-intensity signal (IAS) were manually rated as ASL parameters. A total of 134 patients were evaluated. In the multivariable analyses, ASL perfusion deficit [adjusted odds ratio (aOR) = 2.82, 95% confidence interval = 1.27–6.27] was positively associated with ERIL. Furthermore, when ATA was accompanied, the ASL perfusion deficit was not associated with ERIL occurrence. Meanwhile, IAS showed a synergistic effect with ASL perfusion deficit on the occurrence of ERIL. In conclusion, we demonstrated the association between perfusion deficits in multiphase ASL with ERIL in patients with AIS. This close association was attenuated by ATA and was enhanced by IAS. ASL parameters may help identify high-risk patients of ERIL occurrence during the acute period.

The bright vessel sign on arterial spin labeling MRI for heralding and localizing large vessel occlusions

BACKGROUND AND PURPOSE

The significance of a bright vessel sign (BVS) at the site of a large vessel occlusion (LVO) on MR arterial spin labeling (ASL) sequence is not widely reported. We compared the utility of the ASL BVS to the gradient echo (GRE) susceptibility vessel sign (SVS) in heralding and localizing LVOs in a large cohort; most underwent digital subtraction angiography (DSA) and endovascular therapy for acute stroke.

METHODS

A total of 171 patients with large hemispheric stroke symptoms had baseline and follow-up MRIs with ASL, GRE, and MR angiogram (MRA). Scans were evaluated for (1) presence versus absence and (2) location of ASL BVS and GRE SVS. For patients who underwent DSA, data comparing presence and location of ASL BVS and GRE SVS to occlusions found on angiography, as well as resolution of the signs after successful recanalization, were also evaluated.

RESULTS

Compared to MRA, the sensitivity of the ASL BVS for an LVO was .83, significantly better than .67 for GRE SVS (p = .001). Localization of vessel occlusion was correct 60.4% of the time by ASL compared to 64.4% by GRE (p = .502). For the 107 patients who underwent DSA, the sensitivity of ASL BVS was .80 compared to .64 for GRE SVS (p = .009). Localization of LVO found on DSA was correct 63.5% of the time by ASL BVS compared to 72.9% by GRE SVS (p = .251).

CONCLUSION

ASL BVS is significantly more sensitive than GRE SVS for identification of LVO on both MRA and DSA.

Addition of arterial spin-labelled MR perfusion to conventional brain MRI: clinical experience in a retrospective cohort study

OBJECTIVE

The usage of arterial spin labelling (ASL) perfusion has exponentially increased due to improved and faster acquisition time and ease of postprocessing. We aimed to report potential additional findings obtained by adding ASL to routine unenhanced brain MRI for patients being scanned in a hospital setting for various neurological indications.

DESIGN

Retrospective.

SETTING

Large tertiary hospital.

PARTICIPANTS

676 patients.

PRIMARY OUTCOME

Additional findings from ASL sequence compared with conventional MRI.

RESULTS

Our patient cohorts consisted of 676 patients with 257 with acute infarcts and 419 without an infarct. Additional findings from ASL were observed in 13.9% (94/676) of patients. In the non-infarct group, additional findings from ASL were observed in 7.4% (31/419) of patients, whereas in patients with an acute infarct, supplemental information was obtained in 24.5% (63/257) of patients.

CONCLUSION

The addition of an ASL sequence to routine brain MRI in a hospital setting provides additional findings compared with conventional brain MRI in about 7.4% of patients with additional supplementary information in 24.5% of patients with acute infarct.

Spatial coefficient of variation of arterial spin labeling MRI as a cerebrovascular correlate of carotid occlusive disease

Clinical interpretation of arterial spin labeling (ASL) perfusion MRI in cerebrovascular disease remains challenging mainly because of the method's sensitivity to concomitant contributions from both intravascular and tissue compartments. While acquisition of multi-delay images can differentiate between the two contributions, the prolonged acquisition is prone to artifacts and not practical for clinical applications. Here, the utility of the spatial coefficient of variation (sCoV) of a single-delay ASL image as a marker of the intravascular contribution was evaluated by testing the hypothesis that sCoV can detect the effects of differences in label arrival times between ipsi- and contra-lateral hemispheres even in the absence of a hemispheric difference in CBF. Hemispheric lateralization values for sCoV and CBF were computed from ASL images acquired on 28 patients (age 73.9 ± 10.2 years, 8 women) with asymptomatic unilateral carotid occlusion. The results showed that sCoV lateralization predicted the occluded side with 96.4% sensitivity, missing only 1 patient. In contrast, the sensitivity of the CBF lateralization was 71.4%, with 8 patients showing no difference in CBF between hemispheres. The findings demonstrate the potential clinical utility of sCoV as a cerebrovascular correlate of large vessel disease. Using sCoV in tandem with CBF, vascular information can be obtained in image processing without the need for additional scan-time.

A novel visual ranking system based on arterial spin labeling perfusion imaging for evaluating perfusion disturbance in patients with ischemic stroke

We developed a visual ranking system by combining the parenchymal perfusion deficits (PPD) and hyperintense vessel signals (HVS) on arterial spin labeling (ASL) imaging. This study aimed to assess the performance of this ranking system by correlating with subtypes classified based on dynamic susceptibility contrast (DSC) imaging for evaluating the perfusion disturbance observed in patients with ischemic stroke. 32 patients with acute or subacute infarcts detected by DSC imaging were reviewed. Each patient’s brain was divided into 12 areas. ASL ranks were defined by the presence (+) or absence (-) of PPD/HVS as follows; I:–/–, II:–/+, III: +/+, and IV: +/–. DSC imaging findings were categorized based on cerebral blood flow (CBF) and time to peak (TTP) as normal (normal CBF/TTP), mismatched (normal CBF/delayed TTP), and matched (decreased CBF/delayed TTP). Two reviewers rated perfusion abnormalities in the total of 384 areas. The four ASL ranks correlated well with the DSC subtypes (Spearman’s r = 0.82). The performance of ASL ranking system was excellent as indicated by the area under the curve value of 0.94 using either matched or mismatched DSC subtype as the gold standard and 0.97 using only the matched DSC subtype as the gold standard. The two methods were in good-to-excellent agreement (maximum κ-values, 0.86). Inter-observer agreement was excellent (κ-value, 0.98). Although the number of patients was small and the number of dropouts was high, our proposed, ASL-based visual ranking system represented by PPD and HVS provides good, graded estimates of perfusion disturbance that agree well with those obtained by DSC perfusion imaging.

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.

Dural Arterivenous Fistula at the Cavernous Sinus Diagnosed by Arterial Spin-labeled Imaging

We herein report a case of dural arteriovenous fistula (DAVF) at the cavernous sinus that was diagnosed by arterial spin-labeled imaging (ASL). A 67-year-old woman was referred to our hospital due to double vision and bilateral conjunctival injection. Conventional magnetic resonance imaging findings were normal. However, abnormal hyperintense signals on ASL were detected. Furthermore, the abnormality disappeared after successful endovascular embolization. Although conventional digital subtraction angiography is the standard tool for diagnosing DAVF, we speculated that ASL might be useful to this end as well.

Proximal Bright Vessel Sign on Arterial Spin Labeling Magnetic Resonance Imaging in Acute Cardioembolic Cerebral Infarction

BACKGROUND

The congestion of spin-labeled blood at large-vessel occlusion can present as hyperintense signals on perfusion magnetic resonance imaging with 3-dimensional pseudo-continuous arterial spin labeling (proximal bright vessel sign). The purpose of this study was to clarify the difference between proximal bright vessel sign and susceptibility vessel sign in acute cardioembolic cerebral infarction.

METHODS

Forty-two patients with cardioembolic cerebral infarction in the anterior circulation territory underwent magnetic resonance imaging including diffusion-weighted imaging, 3-dimensional pseudo-continuous arterial spin labeling perfusion magnetic resonance imaging, T2*-weighted imaging, and 3-dimensional time-of-flight magnetic resonance angiography using a 3-T magnetic resonance scanner. Visual assessments of proximal bright vessel sign and the susceptibility vessel sign were performed by consensus of 2 experienced neuroradiologists. The relationship between these signs and the occlusion site of magnetic resonance angiography was also investigated.

RESULTS

Among 42 patients with cardioembolic cerebral infarction, 24 patients showed proximal bright vessel sign (57.1%) and 25 showed susceptibility vessel sign (59.5%). There were 19 cases of proximal bright vessel sign and susceptibility vessel sign-clear, 12 cases of proximal bright vessel sign and susceptibility vessel sign-unclear, and 11 mismatched cases. Four out of 6 patients with proximal bright vessel sign-unclear and susceptibility vessel sign-clear showed distal middle cerebral artery occlusion, and 2 out of 5 patients with proximal bright vessel sign-clear and susceptibility vessel sign-unclear showed no occlusion on magnetic resonance angiography.

CONCLUSIONS

Proximal bright vessel sign is almost compatible with susceptibility vessel sign in patients with cardioembolic cerebral infarction.

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.

Distinctive Patterns of Three-Dimensional Arterial Spin-Labeled Perfusion Magnetic Resonance Imaging in Subtypes of Acute Ischemic Stroke

BACKGROUND

Ischemic penumbra in acute ischemic stroke (AIS) can be evaluated using arterial spin-labeled (ASL) perfusion magnetic resonance imaging (MRI). We used three-dimensional ASL-MRI to examine patients with different stroke subtypes and the clinical utility of the method within 24 hours of AIS onset.

SUBJECTS AND METHODS

The 55 male and 48 female patients (mean age, 79.0 years) underwent diffusion-weighted imaging (DWI), fluid-attenuated inversion recovery imaging, magnetic resonance angiography, and pulsed continuous ASL perfusion imaging to determine stroke subtype, hypoperfused ASL area, and neurological deficit severity (National Institutes of Health Stroke Scale). Arterial transit artifacts, indicative of occlusive regions or collateral flow, and other stroke indices were compared.

RESULTS

ASL hypoperfusion was detected in 3 of 9 patients with transient ischemic attack (TIA), 2 of 27 patients with lacunar infarction (LI), 19 of 31 patients with atherothrombotic infarction (AT), and 30 of 36 patients with cardiogenic embolic infarction (CE). ASL abnormalities were significantly less frequent in LI than in AT and CE, and more frequent in CE than in TIA. ASL abnormalities were more prevalent in patients with medium-to-large DWI-assessed lesions than in those with small lesions on DWI. Patients with medium-sized lesions following AT and CE had a high frequency of diffusion-perfusion mismatch. In 4 of the 5 patients who underwent intravenous thrombolytic therapy, ASL hypoperfusion and diffusion-perfusion mismatch were improved and the occluded arteries were recanalized.

CONCLUSIONS

ASL perfusion studies may provide useful clinical information allowing diffusion-perfusion mismatch detection and treatment selection in AIS patients, depending on stroke subtype.