X-ray Production

Excerpt

X-rays are a form of electromagnetic radiation with wavelengths ranging from 0.01 to 10 nanometers. In the setting of diagnostic radiology, X-rays have long enjoyed use in the imaging of body tissues and aid in the diagnosis of disease. Simply understood, the generation of X-rays occurs when electrons are accelerated under a potential difference and turned into electromagnetic radiation. An X-ray tube, with its respective components placed in a vacuum, and a generator, make up the basic components of X-ray production. Essential components of an X-ray tube include a cathode, and an anode separated a short distance from each other, a vacuum enclosure, and high voltage cables forming the X-ray generator attached to the cathode and anode components. In the generation of X-ray production, a cathode filament machined in a cathode cup is activated, causing intense heating of the cathode filament. The heating of the filament leads to the release of electrons in a process called thermionic emission. The released electrons form in an electron cloud at the filament surface, and repulsion forces prevent the ejection of electrons from this negatively charged cloud. Upon application of a high voltage by an X-ray generator to the cathode as well as the anode, there is an acceleration of electrons ejected to an electrically positive anode. The filament and the focusing cup determine this path of acceleration. The number of electrons is measured in the form of milliampere (mA) units, where 1 milliampere is equal to 6.24 x 10^15 electrons/s. Electron kinetic energy (measured in keV) is related to the applied voltage. The tube voltage, tube current, and exposure duration (measured in seconds) are adjustable by the user.