The diagnostics of hyper acute infarction and ischaemia is mainly done by diffusion –weighted imaging (DWI). DWI is sensitive to diffusion of water molecules within tissue. The greater the amount of diffusion, the greater the signal loss in DWI. As such, areas of acute ischaemia show reduced diffusion of water molecules, which will then be, picked up on a MRI.DWI imaging is the most sensitive technique available for the detection …show more content…
MR Angiography.
Time of Flight imaging produces spectacular images of cerebral vasculature and is a sensitive technique for the assessment of cerebral flow, cerebral anatomy and the detection of cerebral aneurysms. For the identification of collaterals and distal occlusions the administration of Gadolinium is necessary.
Another modality in MRI scanning, similar to DWI is Perfusion weighted imaging (PWI). This technique can also be used to calculate the blood supply to a particular volume of the brain. The brain is rapidly scanned following the injection of a bolus, Gadolinium. The data obtained from these scans are then represented in a myriad of ways, including maps of regional cerebral blood volume and the mean transit times. Studies have shown, (Chen & Ni 2012) that in general, the perfusion defects identified with PWI are larger than the diffusion abnormalities shown on DWI. The difference between these scans is referred to as the ischaemic penumbra. The penumbra describes an area of non- infarcted brain that has reduced perfusion and is therefore at risk. The ischaemic penumbra is the centre of a lot of current research as early intervention such as this intra arterial injection of tPA may reduce the amount of brain tissue that eventually becomes infarcted. Which makes these modalities extremely