Computed tomography

Computed tomography (CT) combines X-ray measurements taken from multiple angles to reconstruct cross-sectional images and three-dimensional representations of internal structures.

X-ray attenuation: The reduction in X-ray intensity as radiation passes through matter. Differences in attenuation across tissues provide the measurements CT reconstructs.
X-ray: Electromagnetic radiation with wavelengths shorter than ultraviolet light, capable of penetrating matter. CT uses X-rays as its penetrating probe.
Computed tomography angiography: A CT technique that images blood vessels after injection of an iodinated contrast agent. It adapts CT acquisition to depict arteries and veins.
Magnetic resonance imaging: An imaging method that uses magnetic fields and radiofrequency signals to create images, especially of soft tissues. MRI avoids ionizing radiation and often offers stronger soft-tissue contrast than CT.
Medical radiation exposure: Exposure to ionizing radiation from diagnostic or therapeutic medical procedures. CT's X-rays create a dose that must be balanced against diagnostic benefit.
Radon transform: A mathematical transform that maps a function to its integrals along lines. CT projections approximate line integrals of the body's attenuation map.
Projectional radiography: An imaging technique that records a two-dimensional shadow of structures using X-rays. Unlike a radiograph, CT separates overlapping anatomy into cross-sectional images.
CT pulmonary angiography: A contrast-enhanced CT examination designed to detect pulmonary artery abnormalities, especially emboli. It is a focused CT application for suspected pulmonary embolism.
Ultrasound: An imaging method that forms images from high-frequency sound waves and their echoes. Ultrasound avoids X-rays but cannot image through bone or air as CT can.
Radiation dose index: A quantity used to characterize radiation output in computed tomography examinations. CT dose indices help describe and compare scanner output, though they are not individual risk estimates.

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