Slide 1
Many views become a slice
Computed tomography, or CT, uses X-ray measurements from multiple angles. A computer reconstructs cross-sections through the body.
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An ordinary projection superimposes depths. CT instead estimates how attenuation is distributed within a section, making it easier to distinguish structures that lie behind one another.
Slide 2
Rotation collects the evidence
An X-ray source and detector system rotate around the patient. Their changing viewpoints provide the measurements used in reconstruction.
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Movement during acquisition can create artifacts because the calculation expects compatible views of the same anatomy. The image is computed, but it still depends on the quality of the measurements.
Slide 3
Slices can form a volume
A series of reconstructed slices can be assembled into a volume. The data can then be viewed in several planes.
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A three-dimensional display is another representation of the same underlying scan. It may help communicate spatial relationships without providing an independent second observation.
Slide 4
Contrast changes visibility
A contrast agent can make selected structures easier to distinguish. The examination is designed around the tissue or process being investigated.
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Timing matters when contrast travels through blood vessels. A scan aimed at one phase of circulation may answer a different question from an otherwise similar scan acquired later.
Slide 5
Detail has trade-offs
CT provides valuable cross-sectional information but uses ionizing radiation. Scan settings and the decision to scan depend on the clinical purpose.
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More images do not automatically mean better care. An appropriate examination supplies information likely to change understanding or management while avoiding unnecessary acquisition.
Sources
- Computed Tomography (CT)
NIBIB, NIH
- Body CT
ACR and RSNA, RadiologyInfo