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An image acquisition process that produces an electronic image viewable and manipulable on a computer.
Digital Radiography
Devices used in DR that convert x-rays to charge for digital image processing, using direct or indirect conversion.
Flat Panel Detectors
what type of capture converts x-ray photons to electrical signals
Direct Capture
What type of capture converts the incoming x-ray photons first to light then electrical signal to the final digital image
Indirect Capture
Advantages of DR
Lower patient exposure due to low imaging failure rate
high speed of image acquisition,
excellent image quality, and
high-speed workflow.
Disadvantages of DR
Limited flexibility for difficult views and
high initial investment costs.
A matrix of picture elements or pixel
Digital Image
Box of cells with numeric value arranged in rows and columns
Matrix
Represents the level of brightness or intensity at the location in the image
Numeric value
TRUE or FALSE. An image is formed by a matrix of pixels
True
TRUE or FALSE. The size of the matrix is described by the number of pixels in the rows and columns
True
The basic unit of a digital image, capable of representing various shades of gray in the matrix.
Pixel
Formula for Pixel Size
Pixel Size = FOV/Matrix Size
It refers to the number of pixels present on a digital image
Pixel Density
The distance between the center of one pixel to one adjacent pixels
Pixel Pitch
Relationship of Pixel Pitch and Pixel Density
Inversely Proportional
Relationship of Pixel Density and Pixel Pitch to Spatial Resolution
Direct Proportional for Pixel Density and Spatial Resolution
Inversely Proportional for Pixel Pitch and Spatial Resolution
The number of bits per pixel that determines the shades of gray in an image.
Bit Depth
Most digital radiography systems use an ____ of bit depth
8, 10, or 12 Bit Depth
It is determined by the analog to digital converter
Bit Depth
A square arrangement of numbers in rows and columns.
Matrix
Each box within the matrix corresponds to: (2 answer)
A specific location in the image
A specific area of the patient’s tissue
The extent of the patient imaged in the matrix
Field of View (FOV)
TRUE OR FALSE. Smaller FOV, the greater the amount of body part is included in the image
False
TRUE or FALSE. Changes in either the FOV or the matrix size will change the pixel size
True
TRUE OR FALSE. Matrix Size and the FOV are dependent
False
A measure of how efficiently a digital detector converts x-rays into a useful image.
Detective Quantum Efficiency (DQE)
The DQE for a perfect digital detector is?
1 or 100%; no loss of information
A measure of the amount of exposure on the image receptor
Exposure Index
The ability of the imaging system to allow two adjacent structures to be visualized as being separated or distinctness of an image to the image
Spatial Resolution
Refers to the smallest object that can be detected in an image; term usually used in digital imaging
Spatial resolution
The ability to differentiate shades of gray, indicating the imaging receptor's capability to distinguish similar contrasts.
Contrast Resolution
The principal descriptor for contrast resolution is
Dynamic Range
The number of gray shades an imaging system can produce; the ability of the detector to capture accurately the range of photon intensities that exit the patient
Dynamic Range
Dynamic range of digital imaging system is identified by the?
Bit capacity of each pixel
A method of describing the strength of radiation exposure compared to noise in a digital image.
Signal-to-Noise Ratio (SNR)
TRUE or FALSE. Decreasing the SNR improve quality of the digital image
False
Solid-state image receptors that convert x-ray photons to electrical charges for storage and readout; also called Digital Receptors
Flat Panel Detectors
What integrated into the flat panel device
Signal Storage
Signal readout
Digitizing electronics
Are highly dose-efficient and provide quicker access to images
Flat panel System
Three layers of Thin Flat Panel Detector for Indirect Capture
Scintillation Layer
Photodiode Layer
Thin Flat-Panel Transistors
The layer that converts X-rays into small bursts of light energy, is typically made from Cesium Iodide or Gadolinium Oxysulfides.
Scintillation Layer
The preferred material of the Scintillation Layer; has a needlike structure that produces more focused light beam that increases spatial resolution
Cesium Iodide
A layers that converts incoming light photons into electric charge, usually made of Amorphous Selenium.
Photodiode Layer
Amorphous means
without shape or form
What is the process of making the Photodiode Layer; where the amorphous is liquid that can be painted onto a supporting surface
Plasma-Enhanced chemical vapor deposition
It is the both the capture element and coupling element. Limits diffusion of electrons and maintains excellent spatial resolution
Amorphous Selenium
Thickness of Amorphous Selenium
High approx. 200 um thick; sandwich between charged electrons
Temporarily stores electrical charges by the capacitors before digitization and processing.
Thin Flat Panel Transistor (TFT) Layer
TFT comprised of an array or matrix of
Digital elements (DEL)
Detector elements has three components
TFT
Capacitor
Sensing Area
Temporarily store the electrical charge
Capacitors
Acts to open and close the analog signal leaving each DEL
TFT/Switch
An oldest indirect conversion radiography system to acquire a digital image; it is a silicon-based semiconductor
Charged Couple Device (CCD)
Charged Couple Device developed in what year
1970s; highly sensitive device for military use
CCD Three principal advantage
Sensitivity; respond to low lvls of visible light
Dynamic Range; detects from very dim light to intense light
Size; 1- 2 cm
Thin Flat Panel Detectors for Direct Capture has two layers
Semi-conductor
Thin Film Transistor
Determines Pixel density of digital image
Pixel Pitch
