Table 1.
Imaging techniques used for assessment of AIS.
| Imaging technique | Use in stroke | Benefits (✓) and drawbacks (×) | |
|---|---|---|---|
| Non contrast computed tomography (NCCT) | Diagnosis of major stroke. Identify a contraindication to treatment, like hemorrhage or large infarct. Identify stroke mimic such as brain tumor |
✓ Fast and widely available × Insensitive to the diagnosis of minor stroke due to low spatial resolution (13) × Moderate interrater reliability, even between experts (14) |
|
| Computed tomography angiography (CTA) | Detection of large vessel occlusion (LVO) | ✓ Detects LVO with almost 100% sensitivity × Constrast agent is required (typically iodine) |
|
| Single-phase CT angiography (sCTA) | Allows the assessment of the global colateral circulation (15) | ✓ Rapid evaluation of the presence of intracranial LVO × Single image; no temporal resolution |
|
| Multiphase CTA (mCTA) | Provides time-resolved images of the cerebral vasculature with 3 cerebral image acquisitions | ✓ Can be acquired in 30 seconds, thus lesser motion artifacts ✓ Good interrater reliability ✓ Excellent predictor of clinical outcome (16) × Higher radiation dose compared to sCTA but lower radiation dose than CTP × Interpretation requires high degree of expertise |
|
| CT perfusion (CTP) or perfusion computed tomography (PCT) | Time-resolved images of blood flow Display format is perfusion maps, including CBF, CBV, and MTT. Used to identify and quantify volume of infarcted core and penumbra |
✓ Easier to interpret than CTA ✓ Easy availability, rapid acquisition × Long image-acquisition times (continuous scanning for 45–90 seconds) × Susceptible to motion artefacts × More radiation exposure compared to CTA as additional contrast dose required × Complex acquisition and heterogeneous postprocessing algorithms (17) |
|
| Digital subtraction angiography (DSA) | Old technology. Classical evaluation of circulation status |
× Time consuming invasive technique, only justified in the case of mechanical thrombectomy × Bilateral carotid and vertebral injections are required |
|
| MRI | Most sensitive technique for AIS detection. Used in imaging diagnosis of minor stroke and typically during follow-up (18) | ✓ Excelllent spatial resolution ✓ Can detect brain ischemia in transient ischemic attack or minor ischemic stroke ✓ Can be conducted without the application of contrast agents (DWI, SWI, ASL) but for early diagnostic purposes contrast agents are used × Time-consuming, fastest protocol takes 6 min (19) × Susceptible to motion artefacts × May not be available 24 h in many centers |
|
| Diffusion MRI or diffusion-weighted imaging (DWI) | Used to obtain the perfusion fraction. Used to accurately quantify volume of infarcted core |
✓ High (73–92%) sensitivity 3h and ~100% sensitivity 6h after onset (20) × ADC values can be affected by flow apart from diffusion (21) |
|
| Susceptibility weighted imaging (SWI) | Used to evaluate cerebral microbleeds | × Artifacts can be produced from patient motion | |
| MR angiography (MRA) | Used in patients with a contraindication to contrast or a non-diagnostic CTA (22) | × MRA is not needed if CTA is performed | |
| Non-contrast enhanced MRA time-of-flight (TOF) | Measures and illustrates the flow of blood inside vessel structures in 2D and 3D (23) | × Poor depiction of some areas or thrombus shine through might lead to misdiagnosis of occlusion (24) | |
| Non-contrast enhanced MRA. Phase-contrast | Non-contrast-enhanced MRA with a high rate of background suppression. Used for better visualization of cerebral blood flow |
✓ Good spatial resolution | |
| Contrast enhanced-MRA | ✓ Shorter acquisition time than non contrast MRA ✓ less susceptible to patient motion × Uses gadolinium-based contrast agent × Requires intravenous access and contrast administration × Decreased spatial resolution compared to TOF (20) |
||
| MR Perfusion | Arterial spin labeling (ASL) | Used to quantify volume of infarcted core (using either DWI or ASL). Used for estimating brain perfusion to core and penumbra |
✓ Prefered over CTP when available to avoid radiation exposure ✓ Non-contrast-enhanced technique × Sensitive to susceptibility artifacts, motion artifacts |
ICA, internal carotid artery; MCA, middle cerebral artery; EVT, endovascular therapy; CBF, cerebral blood flow; CBV, cerebral blood volume; MTT, mean transit time; CC, colateral circulation; ADC, apparent diffusion coefficient; IVIM, intravoxel incoherent motion imaging.