| Term | Definition |
|---|
| Milliamperage (mA) | A unit of current that is one thousandth of an ampere; unit used to measure the rate of current flow in an x-ray tube; it is used to describe the exposure setting of a radiography machine that determines the rate of which x-rays are produced |
| Milliamperage seconds (mAs) | The product obtained by multiplying the electric current in milliamperes by the exposure time in seconds; is indicative of the total quantity of radiation involved in an exposure and determines the density of the radiographic image |
| Nonstochastic | Describes biologic radiation effects that are predictable and their intensity is does-dependent. These effects occur only after a certain threshold amount of exposure has been received |
| Photon | The smallest quantity of electromagnetic energy; it has no energy and no charge and travels at the speed of light; photons may occur in the form of light rays, x-rays, gamma rays, and other electromagnetic energies |
| Quantum | A group of "bundle" photons |
| Rad | Abbreviation for radiation absorbed dose, the basic unit of absorbed dose of ionizing radiation in the British system of radiation measurement; one ___ is equal to the absorption of 100 ergs of radiation energy per gram of matter |
| Roentgen equivalent in man (rem) | The radiation dose equivalent unit in the British system of radiation measurement. Its value is obtained by muliplying the absorbed dose in rad times the weighting factor of the specific type of radiation involved |
| Roentgen (R) | The standard unit of radiation exposure in the British system of radiation measurement, it is a measurement of radiation intensity in air; is equal to the quantity of radiation that will produce 2.08 x 10^9 ion pairs in a cubic centimeter of dry air |
| Source-image distance (SID) | The distance between the x-ray tube target and the image receptor, measured along the central ray; insures patient safety during radiographic procedures; 40" for most routines, 72" for chest x-rays |
| Stochastic | Describes biologic radiation effects that are random and unpredictable; their likelihood is dose-dependent, but not their severity. There is no threshold amount of exposure necessary to produce these effects |
| Wavelength | With respect to a sine wave, the distance between a given point on one wave cycle and the corresponding point on the next successive wave cycle |
| Weighting factor (WF) | An approximate measure of the relative biological effectiveness of a particular radiation compared with a reference radiation; reference is 250 keV x-rays; is mulitplied by the dose to determine the dose equivalent; formerly termed quality factor (QF) |
| Scatter radiation | Produced when a primary x-ray beam interacts with patient tissue; degrades image quality |
| Portable x-ray machine | Used when patients can not come down to x-ray department; ICU's, patient floors, neonatal nursery, OR |
| Contrast media | Allows for visualization of organs not seen on plain radiographs (e.g. GI tract, blood vessels, urinary system); administered to the patient either orally or intravenously |
| Image receptor | Used to capture the radiographic image of the body; e.g. cassettes, photostimulable imaging plates (computed radiography), flat panel detector plates (digital radioraphy) |
| Intensifying screen | Found inside of cassettes; made of phosphor, either calcium tungstate or rare earth phosphor; emits light when struck by x-ray; enables tech to use much less x-ray exposure |
| Film | Primary medium used to record the radiographic image; sensitive to light and x-rays; called a radiograph after x-ray exposure and development |
| Pass box | Allows cassettes to be passed back and forth between darkroom and lightroom |
| Dark room | Where most radiographs are developed; tech will unload exposed film from cassette, feed into the auto processor, and reload the cassette |
| Daylight processing | Special process that eliminates the need for a darkroom; utilizes spring loaded cassettes; allows film to pass into daylight processors without being exposed to light |
| Digital imaging | Called "filmless" radiography, as film/screen cassettes are replaced by computer plates and detectors; images are displayed on CRT monitors; eliminates the need for film processors and darkrooms |
| Density | Overall blackening of a radiograph |
| Contrast | Density differences and shades of gray |
| Detail | Sharpness of an image |
| Distortion | Magnification of part or all of the image |
| Blur | Greatest detractor of image quality usually caused by patient motion during imaging |
| Computed tomography (CT) | Uses x-rays and computer detectors to image cross sections of the body |
| Magnetic resonance imaging (MRI) | Uses radiofrequency waves within a magnetic field and computer detectors to image cross sections of the body |
Combine with other sets
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