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Several studies have been conducted to determine the “best” imaging modality in acute stroke,but the reality is that both CT and MRI will co-exist and complement each other for a long time.The main drawbacks to CT are that an ischemic brain stroke may not appear in a CT scan forup to 48 hours period, and that CT does not image the vertebra-basilar (up to 15% of strokes).While the MRI does provide superior quality of images and anatomical details, in an acute settingits advantages address the above-mentioned two drawbacks of CT. Important contraindicationsto MRI are patients with magnetic material in their body such as pacemakers, pins, a vital pointto note as neurologically altered or aphasic patients may be unable to provide this information totheir providers.<ref name=Mirza2016/> The sensitivities and specificities were 100% and 86%, respectively, for diffusion-weightedMR imaging versus 18% and 100% for conventional MR imaging and 45% and 100% for CT .New guidelines from the American Academy of Neurology state that doctors should use a diffusionMRI scan to diagnose stroke instead of a CT scan which was published in the July 13, 2010, issueof Neurology®, the medical journal of the American Academy of Neurology.The imaging modality of choice will depend upon the specific situation: cost, availability,clinical setting, contraindications etc. and it remains the purview of a well-educated provider todetermine the imaging to effectively guide the therapeutic goals.<ref name=Mirza2016/> {|classSee also="wikitable"|+ Table 1: CT vs MRI<ref name=Mirza2016/>! Characteristic !! *[[CT !! MRI|-| Availability || Easily available in of the emergency department || Not available in all emergency departments|-| Time || 5 mins || 15 mins|-| Perfusion study: volume assessed || 2–4 cm || Entire brain visualized|-| Side effects: Contrast | Iodinated contrast has toxic effects on kidney, cannot be used head in renally compromised patients, risk of anaphylaxis.| Gadolinium: minimal toxicity on kidneys, risk of nephrogenic and systemic fibrosis|-| Side effects: Ionizing radiation || YES: increases risk of cancer || No ionizing radiation|-| Side effects: Claustrophobia || - || +++|-| Drawback: motion artefact || + || +++|-| Contraindication: Pacemaker, shrapnel, metal plates || - || +++|-!colspan=3| Purpose|-| Chronic hemorrhage || +/- || +++|-| Acute ischemic stroke || - || ++|-| Angiography || ++ || +++|-| Vertebro-basilar visualization || - || ++|-|colspan=3| Abbreviations: ICH: Intracerebral hemorrhage, SAH: Sub arachnoid hemorrhage, EDH: Extradural hemorrhage, SDH: Subdural hemorrhage. AVM: Arterio-venous malformation, TCD: transcranial Doppler, CDUS: Carotid duplex ultrasound, DSA: Digital subtraction Angiography.|}]]
→MRI - timing and therapeutic windows: Moved to separate page
benefit from interventions even if outside the 3-4.5 hour window.<ref name=Mirza2016/>
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