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

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

negative contrast media

air

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

Positive contrast media

barium and iodine

postprocessing

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

the 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)

Xray beam that exits the patient; is made up of image-forming rays and scatter radiation

RIS

Radiology Information System

Scatter radiation

x-ray 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.

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.

spatial resolution

the sharpness of the structural edges recorded in the image, the smallest detail that can be detected

Surgical Radiography

radiographic procedures performed by the radiographer in the OR, usually using a C-arm or portable fluoroscope.

time, distance, shielding

The 3 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