Test 4 Flashcards
Phosphor -
Europium barium fluorohalide crystals
PSP/IP - Photostimulable Phosphor/Image Plate -
plate used in CR in place of film
Anti-halo/Reflective -
Prevents laser light from penetrating; Allow reflected light from the phosphor to pass through.
Conductive -
Removes static electricity
Base -
PET - polyethylene terephthalate
Backing -
Protects base from handling damage, contains bar code label on IR
Europium Barium Fluorohalide -
X-ray energy enters these molecules, that energy is absorbed by the molecules
F-centers -
Electrons elevated out of their normal orbital rings into higher orbitals.
Fading -
The process of image weakening from latent image being stored on a cassette and not processed immediately.
Readout -
Scan of phosphor plate with helium-neon laser light and reads the latent image from the phosphor.
Raster -
A side to side pattern a laser uses to obtain an image.
Helium-Neon laser - (HeNe) -
Type of laser light used to read the latent image from the phosphor
Latent image -
the image held in the chemical code
Digitizing -
the process of translating an analog image into a binary code
Binary Code -
numerical code of digits 1 & 0’s that computers can see, process, and transfer information
QDE - Quantum Detection Efficiency -
measures the efficiency of a CR system to convert remnant radiation into useful image signals
Contrast resolution -
the ability to distinguish adjacent structures that have similar densities
Exposure Indicators -
the amount of radiation received by the cr imaging plate
Fuji - (the “s” number) -
the exposure indicator for Fuji brand
Fuji - Expectation range
180-220
Fuji - Perfect Exposure Indicator
200
Fuji - Direct or Indirect relationship to dose -
indirect
Kodak - (the “EI” number) -
exposure indicator number for Kodak
Kodak - Expectation range:
1950-2050
Kodak Perfect Exposure Indicator:
2000
Kodak Direct or Indirect relationship to dose:
direct relationship
Agfa - (the “LGM” number) -
The Agfa CR exposure indicator
Agfa Expectation range:
1.9-2.5 LGM
Agfa Perfect Exposure Indicator:
2.2 LGM
Agfa Direct or Indirect relationship to dose -
direct relationship
Quantum mottle -
Noise
Too few X-rays in the beam to adequately form an image
Analog -
A device or system that represents information as continuously variable physical quantities.
Like a mechanical watch.
X-ray film is analog.
Digital -
Device or system that represents information as continuously variable numerical values.
Like a digital watch.
CR & DR are digital.
FPD - Flat Panel Detector (DR Imaging Plate) -
Takes the place of cassettes and readers; 3 different types:
Tethered (w/cord)
Fixed (mounted in Bucky)
Wireless (uses radio signal sent from FPD to base)
Capture element -
Remnant X-ray energy is captured.
Indirect DR - amorphous Sillicon
- converts X-ray to visible light
Coupling element -
Transfers X-ray generated signal to collection element
Indirect DR - amorphous silicon
- light sent to photoconductive material
Collection element -
Collects photons or electrons to be quantified - assigned a digital value
Indirect DR -TFT -
electrons from photoconductive material collected by TFT
Algorithm -
A finite sequence of instructions, an explicit step by step procedure for solving a problem, often used for calculation and data processing. A computers mathematical “recipe”, not one size fits all
Sampling -
The process used to digitize the spatial information in an image, typically achieved by dividing an image into a square or rectanglar array of sampling points.
Spatial resolution -
The ability to see really small structures, the field of view, matrix size
Pixel size -
Measured from side to side of the pixel, a less accurate measure, does not account for dead zones
Pixel pitch -
Measures center of pixel to center of other; takes into consideration dead zones, a more accurate assessment.
Pixel density -
the number of pixels per given area #/mm
Cesium Iodide -
the scintillating phosphor material used in medical imaging specifically for the needle like crystals
Why Cesium Iodide?? -
needle like crystals
Amorphous -
having no shape or organization
Indirect Conversion Flat Panel Detectors -
Detector that uses thin layers of amorphous silicon with an array of photodiodes - coated w/Photostimulable phosphor that emits light - converted to an electrical charge, signal sent to ADC to convert to digital signal.
Amorphous Silicon - (a-Si) -
Phosphor material - emits light when stimulated
Direct Conversion Flat Panel Detectors -
Uses a amorphous selenium coated TFT that directly converts X-ray to electrical signals. Absorbs remnant radiation in the selenium layers that are collected by capacitors, then sent to the ADC to convert to digital.
Amorphous Selenium - (a-Se) -
Absorbs X-ray - converts directly to electrons (no light divergence)
TFT - Thin Film Transistor -
Collect electric charges, positioned in a matrix, detects charges on a pixel by pixel basis.
Capable of very high spatial resolution (greater than 20lp/mm)
AMA - Active Matrix Array -
Amorphous silicon, capacitor, and TFT assembly
DEL - Detector Element -
Small square capable of recording a certain number of electrons.
The smallest possible dot of information.
Capacitor -
Temporarily collects electrical signal
Matrix -
The layout of cells in rows and columns containing pixels/voxels. The larger the matrix, the better the resolution.
Hounsfeld Units/CT Numbers -
a quantitive scale for describing radio density calculated by comparing the linear attenuation coefficient of each pixel
Dot/Matrix image -
A 2 dimensional patterned array, used to represent characters, symbols and images
LP/mm - Line Pairs per Millimeter -
The measure of image sharpness. The ability of the human eye to see the number of high contrast pairs of lines appearing in the space of a single mm.
Pixel -
the smallest component of a picture, 2 dimensional - length x width.
Each pixel corresponds to a shade of gray.
Voxel -
3 dimensional, volume element (CT scan) each voxel corresponds to a shade of gray representing a volume within a patient.
Dynamic Range/Bit range/Bit Depth/Pixel Depth -
The range of gray shades that can be assigned to a pixel, the higher the range, the more gray shades available to display the image.
Scintillation -
xray photons are converted to light within the flat panel detector by a layer of cesium iodide amorphous silicon
The divergent properties of light -
Spreads out across all directions.
The goal of ALL digital imaging systems is to convert x-ray energy into electron energy. Why?
Because electrons can be counted, either individually or as a sum negative charge. Counting something allows you to assign it a digital value. Computers can store information held as numbers (digital information held in a binary code), but they cannot store analog information.
