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Physics
| Term | Definition |
|---|---|
| 15% rule | a 15% increase in kVp is the equivalent to doubling the mAs |
| Absorption | those x-ray photons removed from the x-ray beam as a result of the uptake of their energy by body tissues |
| Actual focal spot | area actually bombarded w/ filament electrons |
| Annihilation reaction | The positron is an “unnatural particle” and, as such, travels until it strikes an electron. In this annihilation event, the positron & the electron it interacts w/ are destroyed & their energy is converted into 2 x-ray photons |
| Anode cooling chart | used to determine the time it takes for the anode to cool based on the factors giving |
| Beam quality | *The penetrating power of the x-ray beam. Measured by the half-value layer (HVL) *Is affected by kVp & filtration & controlled mainly by adjusting kVP |
| Beam quantity | *The total # of x-ray photons in the beam *Is affected by mAs, kVp, & filtration *Is directly proportional to mAs |
| Bremsstrahlung interaction | - an interaction in which a filament electron is attracted to the nucleus, causing it to slow down & change direction. The energy loss is emitted as a bremsstrahlung photon |
| Characteristic cascade | the process of the outer-shell electron filling inner-shell vacancies, creating a cascading effect during a characteristic interaction |
| Characteristic interaction | an interaction in which a filament electron removes an orbital electron from an atom; to regain stability, an outer-shell electron fills the vacancy, giving up its excess energy as a characteristic x-ray photon |
| Classical interaction | An interaction that occurs w/ low-energy x-rays, typically below the diagnostic range. The incoming photon interacts w/ the atom, causing it to become excited. The x-ray does not lose energy, but changes direction |
| Compton electron | the electron ejected from an atom during a Compton scattering event |
| Compton scattering | an interaction in which an incident photon enters a tissue atom, interacts w/ an orbital electron, & removes it from its shell. In doing so, the incident photon loses up to one-third of its energy & is usually deflected in a new direction |
| Continuous emission spectrum | a graphic representation of bremsstrahlung x-ray production |
| Differential absorption | the difference between the x-ray photons that are absorbed photoelectrically versus those that penetrate the body |
| Discrete emission spectrum | a graphic representation of characteristic x-ray production |
| Dual focus tube | *2 small coils of thin tungsten wire *0.1-0.2 mm thick *1-2 mm wide *7-15 mm long *1%-2% thorium sometimes added. Thorium- radioactive metallic element |
| Effective focal spot | the x-ray beam area as seen from the perspective of the patient |
| Extrafocal radiation | is off-focus radiation |
| Half-value layer (HVL) | *Measure the intensity of the beam w/a radiation detector, then placing the aluminum filters thickness between the tube & detector until the intensity reading is reduced 1/2 the original value *Normal HVL-3-5 mm AL |
| Housing cooling chart | used to determine the time it takes for the tube housing to cool |
| incident electron | the electrons from the thermionic cloud that arrive at the anode |
| Inverse square law | states that the intensity of a beam is inversely proportional to the square of the distance. That is the intensity quadruples if the distance is reduced to one half of its original value |
| Negatron | Negative electron |
| Off-focus radiation | *X-ray photons not produced at the focal spot *high voltage electrons striking the focal spot produce scattered electrons/photons *Scattered electrons may have strike another part of the tube & create photons there *25-35% of primary beam |
| Pair production | an interaction that occurs when the incident x-ray photon has enough energy to escape interaction w/ the orbital electrons & interact w/ the nucleus of the tissue atom, resulting in the creation of a positron & an electron |
| Penetration | refers to those x-ray photons that are transmitted through the body & reach the IR |
| Photodisintergration | an interaction in which extremely high-energy photons interact w/ the nucleus of an atom, making it unstable & to regain stability the nucleus ejects a nuclear particle |
| Focal spot | an area on the anode or target that is struck by electrons |
| Photoelectric interaction | an interaction in which the incident x-ray photon interacts w/ the inner-shell electron of a tissue atom & removes it from orbit. In the process, the incident x-ray photon expends all of its energy & is totally absorbed |
| Photoelectron | the electron ejected from an atom during a photoelectric interaction |
| Positron | positively charged electron |
| Primary beam | refers to the x-ray beam as it is upon exiting the collimator & exposing the patient |
| Rayleigh interaction | known as classical interactions |
| Recoil electron | Compton electron or secondary electron |
| Remnant beam | The x-ray beam that remains after interaction w/ the patient & is exiting the patient to expose the IR |
| Secondary photon | characteristic photons produced in ionized tissue atoms as outer-shell electrons fill inner-shell vacancies |
| Space charge effect | the self-limiting factor caused by the space charge reaching a size commensurate w/ the current used & making it difficult for additional electrons to be emitted |
| Therminoic emission | the boiling off of electrons from a filament by a flow of electrical current |
| Thomson interaction | AKA classical interactions |
| Transmission | x-ray photons that pass through the body to expose the IR |
| Tube rating chart | plots 3 technical factors: kVp mA, & exposure time |
| X-ray emission spectrum | a graphic representation of the x-ray beam as a whole, combining the relevant parts of the discrete & continuous emission spectra |
| Secondary electron | the ejected electron resulting from the Compton effect interaction; AKA Compton electron |
Created by:
hicksm0155
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