Imaging the brain’s structure and examining its physiology, both in the acute and elective setting, are now the domain of multiplanar, computer-assisted imaging. The imaging modalities in use today include the following:
Computed Tomography CT
This is the technique of choice for investigation of serious head injury; for suspected intracranial haemorrhage, stroke, infection and other acute neurological emergencies. CT is quick, efficient and safer to use in the emergency situation than MRI.
Magnetic Resonance Imaging MRI
This is the best and most versatile imaging modality for the brain, constrained only by availability, patient acceptability, and the logistics and safety of patient handling in emergency situations. New protocols and higher field strength magnets have raised the sensitivity of MRI in epilepsy imaging, acute stroke, aneurysm detection and follow - up post treatment of neoplastic and vascular disorders. It is the only effective way of diagnosing multiple sclerosis.
Angiography
This is very important in intracranial haemorrhage (ICH), especially subarachnoid haemorrahage (SAH) and, increasing, in intra-arterial management of ischaemic stroke. However, with the widespread availability of multi detector CT scanners, CT angiography CTA is now preferentially used in ischaemic stroke, SAH and ICH. Angiography is still requested for pre-operative assessment of tumors, vascular malformations and angiographic expertise is vital for the performance of many neurointerventional procedures.
Radionuclide Imaging
There are two principal methods. The first is regional cerebral blood flow scanning, still more used in research than in clinical management, especially in the dementias and in movement disorders such as Parkinsonism; second is position emission tomography (PET). By this method focal hyper-metabolism may be shown using 18F fluorodeoxyglucose (18FDG), for example in epilepcy, and cell turnover may be shown using 11C-methionine, for example in tumour studies.
Ultrasound US
This is particularly helpful in neonates and during the first year of life to image haemorrhagic and ischemic syndromes, developmental malformations, and hydrocephalus using the fontanelles as acoustic windows. In adults, transcranial Doppler used for intracerebral arterial velocity studies to assess the severity of vapospasm.
Plain films of the skull
These film are of little value except in head injury.
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