nomenclature

ADC - (analog-to-digital converter) converts image information into numerical data

AEC - (automatic exposure control) ionization chamber located between the patient and the image receptor

algorithm - mathematical formula used by the computer to construct the radiographic image

anode - positive electrode in the x-ray tube

APR; APT - anatomically programmed radiography; anatomically programmed technique; exposure technique is set by the radiographer by choosing the proper anatomic part and projection on the control panel

artifact - an unwanted marking on a radiographic image

automatic collimation - also known as positive beam limitation (PBL); the ability of the radiographic equipment to collimate automatically the x-ray beam to the same size as the image receptor resting in the Bucky tray

bit binary digit - either 1 or 0; the computer’s unit of information

bit depth - the number of shades of gray available within a pixel

blur - effect of motion on the radiographic image

brightness, image brightness - the amount of light coming from the monitor on which the radiographic image is displayed

Bucky - short for Potter-Bucky diaphragm; a moving grid used to remove scatter radiation from the remnant beam, which can cause fog on the image receptor

cassette - container used for holding the imaging plate in computed radiography (CR)

cathode - negative electrode in the x-ray tube

collimator - box-like structure attached to the x-ray tube containing lead shutters that limit the x-ray beam to a specific area of the body

contrast media - solutions or gasses introduced into the body to increase the scale of contrast, making more detail visible; negative contrast medium is air; positive contrast media are barium and iodine

computed radiography (CR) - digital radiographic imaging using a cassette containing an imaging plate

contrast - the visible difference between two selected areas of brightness in the radiographic image; contrast allows detail to be visible

contrast resolution - the smallest change in signal that can be detected by the image receptor

DAP - dose area product, a measure of the total radiation exposure to the patient, extrapolated from the dose in the air just above the patient

DICOM (digital imaging and communications in medicine) - a standard protocol used for blending a picture archiving and communications system and various imaging modalities

direct radiography (DR) - uses fixed detectors that directly communicate with a computer

distortion - misrepresentation of the size or shape of the object as recorded in the radiographic image

dynamic range - the ability of an image receptor to capture the x-ray photons leaving the patient

exposure indicator - describes the status of the exposure and diagnostic value of the digital image

fluoroscopy - “live action” imaging when the x-ray beam is on, creating images of the body as it functions and displaying those images on a monitor

focal spot (focal track) - area of the anode in the x-ray tube from which x-rays emanate

grid - device that is placed between the patient and the image receptor that absorbs scatter radiation exiting the body

HIS - hospital information system

HL7 - health level seven, an international standard for communicating medical information

histogram - graphic display of the distribution of pixel values in a digital image

image receptor (IR) - any device or medium that captures the remnant beam

imaging plate (IP) - plate that is coated with photostimulable phosphors that absorb the photon energies exiting the patient; located inside a computed radiography (CR) cassette

kVp - peak kilovoltage that is applied to the x-ray tube, which determines the wavelength of the x-ray beam and its ability to penetrate the body, impacting the overall contrast of the radiographic image

lead aprons - coverings worn by radiographers who are in a radiographic or fluoroscopic room with the x-ray beam turned on; also required to be worn for radiation protection when performing portable radiography; the lead absorbs most of the scatter radiation that strikes the apron

mAs (milliampere-seconds) - the product of milliamperage and time; mA is the current that is passed through the x-ray tube, whose energy is then converted to x-rays when it strikes the anode; it determines the number of x-rays produced and, consequently, the overall exposure striking the image receptor; radiation exposure to the patient is directly proportional to the mAs used

matrix - digital image that is made up of rows and columns of data

mobile radiography portable radiography - imaging patients in locations other than an x-ray room, such as the patient’s room or operating room (see surgical radiography); because of presence of scatter radiation, the radiographer is required to

wear a dosimeter and lead apron

OID (object-to-image receptor distance) - distance from the part being examined to the image receptor

PACS - picture archiving and communications system

pixel - picture element; the smallest component of a matrix

post processing - digital manipulation of a radiographic image after its acquisition by the computer

PSP (photostimulable phosphor) - coating on the imaging plate of a computed radiography cassette

radiographic image - x-ray image as viewed on a monitor after acquisition

radiographic position - specific position of the body or body part in relation to the table or image receptor

radiographic projection - path the x-ray beam takes as it passes through the body; described as if the body is in the anatomical position

radiographic view - term used to explain how the image receptor sees the body image; the opposite of the radiographic projection

remnant beam (exit radiation) - x-ray beam that exits the patient; is made up of image-forming rays and scatter radiation

RIS - radiology information system

scatter radiation - x-rays emanating from the patient in divergent paths rather than straight to the image receptor; the source of the radiographer’s occupational dose, requiring the wearing of a lead apron and dosimeter for fluoroscopy and mobile

radiography

spatial resolution - the sharpness of the structural edges in the radiographic image; the smallest detail that can be detected

SID (source-to-image receptor distance) - distance from the source of radiation (x-ray tube anode) to the image receptor

SOD (source-to-object distance) - distance from the source of radiation (x-ray tube anode) to the part being examined

surgical radiography - radiographic procedures performed by

the radiographer in the operating room, usually using a C-arm (portable fluoroscope)

time, distance, shielding - the three cardinal principles of radiation protection; least amount of time exposed, greatest distance from the source of radiation, use of lead or other barriers to shield

voxel - volume element; section of tissue represented by a pixel

window level - midpoint of densities in a digital image; used to adjust digital image brightness

window width - adjusts contrast of the digital image

workstation - (radiologist or radiographer) location of the monitor on which radiographic images are displayed

x-ray - a form of electromagnetic radiation at wavelengths that can penetrate matter