Computed tomography of the head
|Computed tomography of the head|
Computer tomography of human brain, from base of the skull to top. Taken with intravenous contrast medium.
|OPS-301 code||3-200, 3-220|
Computed tomography (CT) of the head or Computed Axial Tomography (CAT) scanning uses a series of x-rays of the head taken from many different directions. Typically used for quickly viewing brain injuries, CT scanning uses a computer program that performs a numerical integral calculation (the inverse Radon transform) on the measured x-ray series to estimate how much of an x-ray beam is absorbed in a small volume of the brain. Typically the information is presented as a series of cross sections of the brain.
In approximation, the denser a material is, the whiter a volume of it will appear on the scan, just as in the more familiar "flat" X-rays, where dense bone appears white. CT scans are primarily used for evaluating swelling from tissue damage in the brain, bleeding, and in assessment of ventricle size. Modern CT scanning can provide reasonably good images in a matter of minutes. A spiral CT scan of the head may be performed in 10–30 seconds, making it a good option for children and adults with difficulty holding still for longer periods. The use of contrast dye in CT angiography provides good visualization of the vascular structures and leaks in the blood vessels.
Computed tomography (CT) has become the diagnostic modality of choice for head trauma due to its accuracy, reliability, safety, and wide availability. The changes in microcirculation, impaired auto-regulation, cerebral edema, and axonal injury start as soon as head injury occurs and manifest as clinical, biochemical, and radiological changes. Proper therapeutic management of brain injury is based on correct diagnosis and appreciation of the temporal course of the disease process. CT scan detects and precisely localizes the intracranial hematomas, brain contusions, edema and foreign bodies. Because of the widespread availability of CT, there is reduction in arteriography, surgical intervention and skull radiography.
CT of the head is sometimes used for patients who have sudden hearing loss. This use is not indicated and offers no information which would improve the initial management of the patient. In patients for which there are not other neurological findings, a history of trauma, or a history of ear disease, CT scans should not be used in response to sudden hearing loss.
Special views focusing on the orbit of the eye may be taken to investigate concerns relating to the eye. CT scans are used by physicians specializing in treating the eye (ophthalmologists) to detect foreign bodies (especially metallic objects), fractures, abscesses, cellulitis, sinusitis, bleeding within the skull (intracranial bleeding), proptosis, Graves disease changes in the eye, and evaluation of the orbital apex and cavernous sinus.
Comparison with MRI
Several different views of the head are available, including axial, coronal, reformatted coronal, and reformatted sagittal images. However, coronal images require the patient hyperextend their neck, which must be avoided if any possibility of neck injury exists.
|Wikimedia Commons has media related to Computed tomography images of the brain.|
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