RADT 101: Ch 7 TEST 2

Radiographic Imaging

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 and brightness

Computed Radiography (CR)

Digital images acquisition modality that uses storage phosphor plates to produce images

Contrast

Contrast is the difference between the ranges of adjacent IR exposures represented as gray tones

Contrast Resolution

Ability to distinguish between very subtle differences in image receptor exposures and differentiate them from the noise in the image

Data Drop

Condition due to extreme overexposure, which causes digital detector elements to become overwhelmed with photon energy and leads to drop of data during image reconstruction

Detector Element (DEL)

Pixel-size element of the digital radiography image receptor that has a fixed dimension in x- and y- orientation

Detector Saturation

Data drop that involves areas or regions of the digital detector

Digital Radiography (DR)

Digital image acquisition system that convert x-ray energy into a digital electronic signal for manipulation and display using direct or indirect conversion

Direct Conversion Flat-Panel Detector

Device that converts incident x-ray energy directly into an electronic signal, typically using a photo-conductor as the x-ray absorber and a thing-film transistor as the signal collection area, which sends the electronic signal to the computer for processing and viewing

Distortion

Misrepresentation of the true size or shape of an item

Exposure Indicator

Numeric representation of the quantity of exposure received by a digital image receptor

Exposure Latitude

Range of exposures that produce a diagnostic quality image

Fog

undesirable exposure to the image receptor

Grayscale Bit Depth

Number of shades of gray that can be stored per detector element and displayed per pixel; ranges from 8 bits to 32 bits

Grid

Device consisting of thin lead strips designed to permit primary radiation to pass while absorbing scatter radiation

Half Value Layer

Amount of filtration necessary to reduce the intensity of the radiation beam to one-hald its original value

Image receptor (IR)

Device used to capture the image for recording, such as photo-stimulable phosphor imaging plate or a digital flat-panel detector

Image Receptor (IR) Exposure

Amount of ionizing radiation received by the image receptor

Indirect Conversion Flat-Panel Detector

Device that converts x-ray energy into light; the light is them detected by a charge-coupled device or photodiodes that are coupled with thin film transistors, and converted into an electronic signal that is sent to the computer for processing and viewing

Inverse Square Law

Mathematic formula that describes the relationship between radiation intensity and distance form the source of the radiation

Kilovoltage 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

Raw Image Contrast

Contrast recorded in the image receptor prior to computer processing

Matrix

Series of picture elements (pixels) or detector elements arranged in rows and columns

Milliampere-Seconds (mAs)

Measurement of milliamperage multiplied by the exposure time in seconds, which controls the 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; controlled by the kilovoltage 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

Pixel

Picture element and the smallest component of the matrix

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 of radiant energy with little attenuation

radiopaque

Nost easily penetrable by x-rays or other life forms of radiant energy

Remnant Radiation

Not easily penetrable by x-rays or other forms of radiant energy

Remnant radiation

Radiation resulting after the x-ray beam exits the object

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 Receptor 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 in the image

subject contrast

range of differences in the intensity of the x-ray beam after it has be attenuated by the subject

umbra

the true edge of an object as imaged radiographically

window level

digital image processing parameter that changes displayed image brightness on the monitor, usually throught he use of a mouse

Window Width

Digital image processing parameter that changes displayed image contrast on the monitor, usually through the use of a mouse