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Types of Medical Imaging Techniques

The first imaging techniques developed for medicine, x-rays, were discovered in 1985 by William Roentgen, and they were first used in medicine in 1896 (Lentle and Aldrich, 1997). Early radiology was chiefly concerned with skeletal morphology. Traditional x-rays are recorded on film, but recent developments in digital imaging have led to x-rays images being stored digitally in a computer rather than on film. Modern developments have led to computer tomography scans (CT)in which a fan beam of x-radiation sweeps through 360 degrees while detectors provide a digital readout of the amount of radiation and so the degree to which it has been attenuated, which allows a reconstruction of a sectional display of body structure in terms of electron density. Next came the positron emission tomography (PET) scans which use the emission of positrons during radionuclide decay and their resultant gamma ray production on interaction with electrons to provide an ôautoradiographö of the body. Single gamma rays emitted by radionuclides such as 99mTc, 123I, and 111In are used in single photon emission computer tomography (SPECT) scans which detects tracer distribution in multiple organ sections. Ultrasound is another commonly used imaging device in modern medicine, using sound waves to produce real time images in which signal strength is proportional to reflection from tissue interfaces. Doppler shift analysis - in which the perceived pitch of sound waves varies with the velocity of its source - allows recognition of the velocity and direction of blood flow. Nuclear magnetic resonance imaging (MRI) is used to obtain images of organ structure by using gradient magnetic fields in intersecting coordinates to provide information about the molecular environment of atoms and their spatial location. On a smaller level, magnetometers can be used to detect tiny magnetic fields produced by electrical activity in the brain and image the resulting dipoles (...

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Types of Medical Imaging Techniques. (1969, December 31). In Retrieved 16:27, December 07, 2021, from