The evaluation and management of acute ischemic stroke has primarily relied on the use of conventional CT and MRI techniques as well as lumen imaging sequences such as CT angiography (CTA) and MR angiography (MRA). Several newer or less-established imaging modalities, including vessel wall MRI, transcranial Doppler ultrasonography, and 4D CTA and MRA, are being developed to complement conventional CT and MRI techniques. Vessel wall MRI provides high-resolution analysis of both extracranial and intracranial vasculature to help identify previously occult lesions or characteristics of lesions that may portend a worse natural history. Transcranial Doppler ultrasonography can be used in the acute setting as a minimally invasive way of identifying large vessel occlusions or monitoring the response to stroke treatment. It can also be used to assist in the workup for cryptogenic stroke or to diagnose a patent foramen ovale. Four-dimensional CTA and MRA provide a less invasive alternative to digital subtraction angiography to determine the extent of the clot burden and the degree of collateral blood flow in large vessel occlusions. Along with technological advances, these new imaging modalities are improving the diagnosis, workup, and management of acute ischemic stroke- roles that will continue to expand in the future.
Keywords: CTA = CT angiography; DSA = digital subtraction angiography; ICA = internal carotid artery; IPH = intraplaque hemorrhage; LRNC = lipid-rich necrotic core; MCA = middle cerebral artery; MES = microembolic signal; MPRAGE = magnetization-prepared rapid acquisition gradient echo; MRA = MR angiography; PFO = patent foramen ovale; PICA = posterior inferior cerebellar artery; TCD = transcranial Doppler; TOF = time of flight; TTE = transthoracic echocardiography; VW = vessel wall; four-dimensional CT angiography; four-dimensional MR angiography; imaging; ischemic stroke; transcranial Doppler ultrasound; vessel wall MRI.