Patient Care in Radiography Chapter 2 Key Terms

annotation

any of many types of radiographic markers that may be added to digital images.

automatic exposure control (AEC)

device that terminates the exposure when a specific quantity of radiation has reached the image receptor.

computed radiography (CR)

the method of using a photostimulable phosphor plate to record radiographic images and to digitize them for viewing and storage.

cropping

selecting the desired portion of an image while removing the unwanted remainder of the image.

digital radiography (DR)

Contain radiation receptors within the radiographic table, upright bucky, or stand-alone receptors that transmit digital signals directly to the computer system.

distortion

a variation in the size or shape of the image in comparison to the object it represents.

electronic masking

shuttering or cropping of the digital radiographic field.

exposure index (EI) number

In digital imaging, an exposure indicator number usually displayed on the monitor, also referred to as S number, DI number or other number, depending on the equipment. This number must be monitored by radiographers to ensure that exposures are of diagnostic quality and are not excessive.

exposure time (T)

a measurement of how long the exposure will continue; measured in seconds, fractions of seconds, or milliseconds.

image contrast

the difference in the optical density of adjacent structures within the image.

image detail

refers to sharpness of the image.

inverse-square law

the relationship between radiation intensity and the source-image distance (SID) is inversely proportional to the square of the SID.

kilovoltage (kV or kVp)

a measure of the potential difference across the x-ray tube. (measured at the peak of the electrical cycle) Determines the speed of the electrons in the electron stream; this determines the amount of kinetic energy each electron has when it collides with the target and therefore determines the amount of energy in the resulting x-ray beam.

milliamperage (mA)

a measurement of the current flow rate in the x-ray tube circuit. Determines the number of electrons available to cross the tube and, thus, the rate at which x-rays are produced.

milliampere-seconds (mAs)

indicate the amount of radiation in the exposure.

(mA x T = mAs)

object-image distance (OID)

in radiography, the distance between the object and the image receptor.

optical density (OD)

the overall blackness of the image. (aka radiographic density)

picture archiving and communication system (PACS)

A system that provide archives to store images from all digital imaging modalities, connect images with patient database information, facilitate printing or transfer of images to CD format media, and display both images and information at workstations throughout the network as needed. (allow remote access, transmission of images over telephone lines, etc.).

postprocessing

the use of digital software tools that enable the technologist to manipulate images after they have been viewed and before they are archived.

shuttering

postprocessing software tool that provides a technique for eliminating ambient light around an image.

source-image distance (SID)

the distance between the x-ray tube target and the image receptor, measured along the central ray.