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Chapter 7
Vocab
| Term | Definition |
|---|---|
| Attenuation | Process by which a beam of radiation is reduced in energy when passing through tissue or other materials |
| Automatic Rescaling | Process by which images are produced with uniform brightness and contrast, regardless of the amount of exposure |
| Brightness | Function of a display monitor; changes image lightness/darkness |
| Computed Radiography (CR) | Cassette-based digital radiography; the digital acquisition modality that uses storage phosphor plates to produce images |
| Contrast | Difference between adjacent image receptor (IR) exposures on a radiographic image |
| Data Drop | Condition due to extreme overexposure, which causes digital detector elements to become overwhelmed with photon energy and leads to a drop of data during image reconstruction |
| Density | Degree of darkening or blackness of exposed and processed photographic or radiographic film |
| Detector Saturation | Data drop that involves areas or regions of the digital detector |
| Digital Radiography (DR) | Cassette-less image receptor systems that convert x-ray energy into a digital electronic signal for manipulation and display |
| Direct Capture DR | Devices that convert x-ray energy directly into an electrical signal, typically using a photoconductor as the x-ray absorber and a thin-film transistor as the signal collection area, which then sends the electrical signal to the computer for processing |
| Distortion | Misrepresentation of the true size or shape of an object |
| Exposure Indicator (EI) | Numeric representation of the quantity of exposure received by a digital image receptor |
| Exposure Latitude | Range of exposures that can be used and still result in the capture of a diagnostic-quality image |
| Fog | Undesirable exposure to the image receptor |
| Grid | Device consisting of thin lead strips, designed to permit primary radiation to pass while reducing scatter radiation by absorption |
| Half-Value Layer | Amount of filtration necessary to reduce the intensity of the radiation beam to one half its original value |
| Image Receptor (IR) | Medium used to capture the image for recording, such as x-ray film or a digital imagining plate |
| Indirect Capture DR | Devices that absorb x-rays and convert them into light; the light is then detected by an area-charge-coupled device or thin-film transistor array in concert with photodiodes, and then converted into an electrical signal |
| Intensifying Screen | Layer of luminescent crystals placed inside a cassette to expose x-ray film efficiently and thereby significantly reduce patient dose |
| Inverse Square Law | Mathematic formula that describes the relationship between radiation intensity and distance from the source of radiation |
| Kilovolt Peak (kVp) | Measure of the potential difference, which controls the quality and affects the quantity of x-ray photons produced in the x-ray tube |
| Latent Image | Invisible image created after exposure but before processing |
| Milliampere-Seconds (mAs) | Measurement of milliamperage multiplied by the exposure time in seconds, which controls total quantity of x-ray photons produced in the x-ray tube |
| Penetrating Ability | Ability of an x-ray beam to pass through an object; beam controlled by the kilovolt peak of the beam |
| Penumbra | Fuzzy edge of an object as imaged radiographically; also known as image unsharpness |
| Photon | Quantum or particle of radiant energy |
| Primary Radiation | X-ray beam after it leaves the x-ray tube and before it reaches the object |
| Radiolucent | Permitting the passage of x-rays or other forms or radiant energy with little attenuation |
| Radiopaque | Not easily penetrable by x-rays or other forms of radiant energy |
| Remnant Radiation | Radiation resulting after the x-ray beam exists the x-ray beam |
| Scatter Radiation | Radiation produced from x-ray photon interactions with matter in such a way that the resulting photons have continued in a different direction |
| Source-to-Image Distance (SID) | Distance between the source of the x-rays (usually the focal spot of the x-ray tube) and the image receptor |
| Spatial Resolution | Degree of accuracy of the structural lines actually recorded on the image |
| Umbra | True edge of an object as imaged radiographically |
| Window Level | Image manipulation parameter that changes image brightness on the display monitor, usually through the use of a mouse |
| Window Width | Image manipulation parameter that changes image contrast on the display monitor, usually through the use of the mouse |
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kmccameron
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