Information disappears owing to overlap, tissues with minute absorption coefficients cannot be easily discriminated, and scattering X-rays cause adverse influences on imaging formation. This is generally referred to as radiography. X-rays which penetrate through objects are recorded on films or detectors as two-dimensional images. X-rays are irradiated and penetrate through three-dimensional objects. Röentgen called this radiation type X-ray radiation. This radiation has fluorescence characteristics, sensitizes the film, and penetrates opaque objects. This has been attributed to Wilhelm Conrad Röentgen (Germany) who conducted the first cathode tube experiments (Crookes tube) in Novem. The discovery of X-ray radiation has been a major scientific breakthrough. Keywords : Computed tomography, Physical principle, Clinical application, Technical aspects, Radiation dose The understanding of CT characteristics will provide more effective and accurate patient care in the fields of diagnostics and radiotherapy, and can lead to the improvement of image quality and the optimization of exposure doses. This article reviews the essential physical principles and technical aspects of the CT scanner, including several notable evolutions in CT technology that resulted in the emergence of helical, multidetector, cone beam, portable, dual-energy, and phase-contrast CT, in integrated imaging modalities, such as positron-emission-tomography一CT and single-photon-emission-computed-tomography一CT, and in clinical applications, including image acquisition parameters, CT angiography, image adjustment, versatile image visualizations, volumetric/surface rendering on a computer workstation, radiation treatment planning, and target localization in radiotherapy. Unlike conventional X-ray imaging (general radiography), CT reconstructs cross-sectional anatomical images of the internal structures according to X-ray attenuation coefficients (approximate tissue density) for almost every region in the body. See Beam-hardening artefact, Edge artefact, Mosaic artefact, Ring artefact.Abstract The evolution of X-ray computed tomography (CT) has been based on the discovery of X-rays, the inception of the Radon transform, and the development of X-ray digital data acquisition systems and computer technology. artifact Artefact A structure not normally present, but produced by some external action something artificial the distortion of a substance or signal, which interferes with or obscures the interpretation of a study, or a structure that is not representative of a specimen's in vivo state, or which does not reflect the original sample, but rather the result of an isolation procedure, its handling or other factors artifacts in electronic readout devices–eg, EEG, EKG, and EMG, may be due to loose leads or electrical contacts Cardiac pacing An electrical impulse of noncardiac origin which is recorded as a vertical spike on an EKG or other ECG monitor–eg a pacemaker pulse electrical signals from muscle contractions, or myopotentials, are called muscle artifacts Imaging The artifact seen depends on the procedure–eg, barium enema, where zones of inconstant segmental contractions of the colon may be confused with organic constrictions or anatomic variations, due to mucosal or intramural tumors, or a metal surgical clip that obscures an anatomical structure. For example, in a barium enema, where zones of inconstant segmental contractions of the colon may be confused with organic constrictions or anatomic variations due to mucosal or intramural tumours, or a metal surgical clip that obscures an anatomical structure. The artefact seen depends on the procedure. Artefacts in electronic readout devices (e.g., EEG, EKG, and EMG) may be due to loose leads or electrical contacts.Īn electrical impulse of noncardiac origin which is recorded as a vertical spike on an EKG or other ECG monitor (e.g., a pacemaker pulse) electrical signals from muscle contractions, or myopotentials, are called muscle artefacts.Īny change in tissue that occurs during tissue processing which may alter a tissue’s appearance and possibly the diagnosis. (2) The distortion of a substance or signal which interferes with or obscures the interpretation of a study, or a structure that is not representative of a specimen’s in vivo state, or which does not reflect the original sample, but rather is the result of an isolation procedure, its handling or other factors. artefact (1) A structure not normally present, but produced by some external action something artificial. The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company.
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