MRI of Acute Stroke: What Went Wrong?

Abstract

The news of the recently published trials about the efficacy of intra-arterial interventions for stroke lifted the spirits of all neuroradiologists and the vascular neurology community. [1][2][3][4] Finally, these trials proved our personal experience: Effective early reperfusion of proximal occlusions can save brain parenchyma and improve patient outcomes. Studies were focused on patient selection and fast-treatment workflow to perform interventions as early as possible. In most hospitals, the preferred imaging technique to select patients is CT with CTA and/or CT perfusion, based more on local logistics than on imaging quality or predefined standards. While we are no longer in the era of the early stroke trials, in which imaging with negative findings (ie, CT without hemorrhage) was the indicator for thrombolysis, we are still early in the use of advanced imaging in acute stroke interventions. It seems that just by identifying proximal occlusions, we have improved the selection of patients despite the limitations of CT to demonstrate early definitive lesions in acute stroke. While CT has made great strides in recent years, with perfusion, dual-energy, and other techniques improving and becoming a clear standard, MR imaging techniques seem to have "lost it," at least, in acute stroke.Despite the potential of MR imaging, such as the extreme sensitivity of diffusion techniques, 5,6 its capacity to image the whole brain, and a whole armamentarium of techniques (FLAIR, SWI, MRA, perfusion, and so forth), this potential did not convince most centers to invest in or adapt their workflow to the use of MR imaging over CT. CT evaluation criteria and scores for acute stroke are undisputed. However, their assessment requires experience and can vary considerably among operators. MR imaging is vastly superior in delineating lesion extent, making the differential diagnosis of other conditions, measuring the clot length, and detecting potential "risky" lesions like microbleeds. DWI with or without FLAIR can still demonstrate an early ischemic lesion much better than CT.So, what went wrong with MR imaging in stroke? In the era of the new-generation devices and early and effective reperfusion, has the clear identification of the stroke core lost its importance? One opinion is that use of MR imaging in an emergency setting disturbs the workflow, inhibiting effective treatment. Others might say that without a clear benefit from MR imaging, it is not worth the sacrifice in time to get better image quality. Recent studies have revolutionized the field of acute stroke treatment, but a significant proportion of patients have inadequate reperfusion.1-4 How can we reduce or eliminate the inadequate reperfusion? Can MR imaging-based patient selection be a solution in addition to the improvement of health care systems, prehospital transportation, societal awareness, and hospital workflow improvements?We think that MR imaging can add more information on patient selection for acute stroke and should be the ultimate goal for acute stroke tr...

Predicting Imaging Outcomes in Acute Stroke Therapy—Comparison of Magnetic Resonance Imaging and Computed Tomography

“…Thus, all hope is still not lost for MRI in acute stroke,and we do have a chance to correct the wrongs. 18 Conclusions DWI is more sensitive and specific than noncontrast CT in predicting final infarct volume and can be used as a predictor of functional outcome. However, CT has a major role to rule out acute bleed, as it is fast and reliable.…”

“…Thus, all hope is still not lost for MRI in acute stroke, and we do have a chance to correct the wrongs. 18…”

“…Even collateral assessment, which currently depends on multiphasic CTA, can have surrogate markers of on MRI such as FLAIR (hyperintense vessel sign [HVS]), ASL (arterial transit artefacts/signals [ATA]) as well as mismatch with core (DWI-ASPECTS), apart from looking at postcontrast dynamic MR angiography in future. Thus, all hope is still not lost for MRI in acute stroke, and we do have a chance to correct the wrongs 18. …”

The role of advanced neuroimaging techniques in ischemic stroke prevention

“…14 Haemorrhage exclusion is still best done at the moment with CT. After this comes the need to detect easily an ischemic lesion. MRI is more sensitive in the acute setting: indeed, MRI with diffusion techniques was initially likened to an electrocardiography-like technique for stroke detection 15 –19 – on diffusion imaging, the light-bulb sign will attract attention to a certain ischemic lesion. However, many practical issues made the real implementation of MRI in acute practice difficult.…”

New developments in clinical ischemic stroke prevention and treatment and their imaging implications

“…In fact, very few patients among the five randomized trials underwent pre-endovascular treatment evaluation by MRI. 4–8,105 These limitations of MRI have led to the widespread adoption of CT-based techniques to assess the core infarction.

Figure 5.CT-, PCT-, and MRI-based measures of core infarction in a patient with an acute ischemic stroke.

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