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Definition

Computed tomography (also known as CT, CT scan, CAT, or computerized axial tomography) scans use x rays to produce precise cross-sectional images of anatomical structures.

Description

With the development of modern computers, the scans enhanced digital capabilities allowed the development of computed tomography imaging (derived from the Greek tomos, meaning "to slice"). The diagnostic potential of CT scans was first realized by English physician Godfrey Hounsfield.

CT scans differ from conventional x ray by collecting x rays that have passed through the body (those not absorbed by tissue) with an electronic detector mounted on a rotating frame rather than on film. The x-ray source and collector rotate around the patient as they emit and absorb x rays. CT technology then utilizes advanced computer-based mathematical algorithms to combine different readings or views of a patient into a coherent picture usable for diagnosis.

CT scans increase the scope and safety of imaging procedures that allow physicians to view the arrangement and functioning of the body's internal structures. With particular regard to neurology, CT scans are used to determine the presence or absence of brain tumors. CT scans usually take about an hour and a half, including preparation time, with the actual examination of neural tissue in a brain scan taking 15–45 minutes.

CT scanners are now often combined with positron emission tomography (PET) scanners into one unit. PETCT scanners have the ability to link the functional image created by a PET scan with the anatomical image produced by a CT scan. The combined scanning technique enhances a physician's ability to detect metabolic abnormalities (some no larger than 0.15 in [4 mm] in size) and to precisely map the location of the anomaly.

Increased accuracy reduces the number of unusable results and also results in less retesting.

The combined PET-CT scanners offer physicians the opportunity to differentiate, for example, between Alzheimer's disease and multi-infarct dementia. In addition, the enhanced images allow the differentiation of brain tumors from cerebral necrosis.

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