Computed tomography scan

Computed Tomography Scan is a medical imaging technique that uses computer-processed combinations of many X-ray measurements taken from different angles to produce cross-sectional (tomographic) images (virtual 'slices') of specific areas of a scanned object, allowing the user to see inside the object without cutting.

Overview

The term "computed tomography" (CT) is often used to refer to X-ray CT, because it is the most commonly known form. But, many other types of CT exist, such as Positron emission tomography (PET) and Single-photon emission computed tomography (SPECT).

History

The first commercially viable CT scanner was invented by Sir Godfrey Hounsfield in Hayes, United Kingdom, at EMI Central Research Laboratories using X-rays. Hounsfield conceived his idea in 1967. The first EMI-Scanner was installed in Atkinson Morley Hospital in Wimbledon, England, and the first patient brain-scan was done on 1 October 1971.

Uses

CT scanning of the head is typically used to detect infarctions, tumors, calcifications, haemorrhage and bone trauma. Of the above, hypodense (dark) structures can indicate edema and infarction, hyperdense (bright) structures indicate calcifications and haemorrhage and bone trauma can be seen as disjunction in bone windows.

Risks

The radiation dose for a particular study depends on multiple factors: volume scanned, patient build, number and type of scan sequences, and desired resolution and image quality. In addition, two types of radiation effects have to be distinguished: deterministic and stochastic.

See Also

• X-ray
• Positron emission tomography
• Single-photon emission computed tomography

References

Computed tomography scan Resources
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