LRA-221 Review Flashcards
conventional radiography is also known as -
fil screen / intensifying screen
CR or computed radiography is also known as -
PSP (photostimulable phosphor)
When acquiring an image using DR (Direct radiography), we need to use-
phosphor on a phosphor plate
what type of phosphor is used in PSP (photostimulable phosphor) or phosphor plate?
barium fluorohalide
define photoconductor
- are materials that absorb x-rays, resulting in an electrical charge
- a substance that allows an electrical current to move more easily through it after light shines on it
define scintillator
- phosphors that produce light when absorbing x-rays
define exposure latitude
- the range of exposures that can be recorded as useful densities on a radiographic film for interpretation
- ## Latitude refers to the range of exposure diagnostic image values the image detector is able to produce
define look-up table (LUT)
- look-up table (LUT) is a histogram of the luminance values derived during image acquisition.
- The LUT is used as a reference to evaluate the raw information and correct the luminance values
- This is a mapping function in which all pixels (each with its own specific gray value) are changed to a new gray value
sensitivity speck
- absorbs ejected electrons
- a place in silver halide crystal where latent image is formed, can also trap electrons
- When the X-rays strike the intensifying screen, light is produced
- The light photons and X-ray photons interact with the silver halide grains in the film emulsion, and an electron is ejected from the halide.
- The ejected electron is attracted to the sensitivity speck.
define PAC
- picture archiving and communication
- where images are stored/archived
- network group of computers, servers, and archives that can be used to manage digital images
define DICOM
- standards that allow imaging modalities and PACS to communicate in the same “language”
- made it possible for different manufacturers to communicate
- different departments can communicate with each other
- can send off images to different departments
- associated w/ PACS
define Matrix
- a square arrangement of numbers (pixel values) in columns and rows and in digital imaging, the numbers correspond to discrete pixel values.
define pixels
- picture element
- is the smallest element in a digital image
- contains the smallest divisible component of a digital image
define exposure index
the amount of exposure received by the image receptor (IR), not by the patient
define deviation index
- the difference between the actual exposure (KIND) and the target exposure (KTGT)
- help the technologist determine whether the image has been underexposed or overexposed
- If the DI is negative, the image has been underexposed.
- If the DI is positive, the image has been overexposed.
define contrast resolution
- the ability of the digital system to display subtle changes in the shade of gray.
- digital imaging is directly related to the bit depth of the pixels in the image.
define spatial resolution
The ability of the imaging system to demonstrate small details of an object
define dynamic range
the ability to respond to varying levels of exposure more tissue densities on the digital image are seen, giving the appearance of more detail
define histogram
- a graph representing the range of exposure values recorded by the IR
- representation of the numerical data
define rescaling
images are produced with uniform brightness and contrast, regardless of the amount of exposure used to acquire the image
define edge enhancement
occurs when fewer pixels in the neighborhood are included in the signal average.
define masking
Suppressing frequencies, also known as masking, can result in the loss of small details
define low pass filtering
- also known as smoothing
- smoothing occurs by averaging each pixel’s frequency with surrounding pixel values to remove high-frequency noise.
- result is a reduction of noise and contrast
- Low-pass filtering is useful for viewing small structures such as fine bone tissues.
define high pass filtering
- When the frequencies of areas of interest are known, those frequencies can be amplified and other frequencies suppressed
- increases contrast and edge enhancement
- useful for enhancing large structures such as organs and soft tissues, but it can be noisy
define FPD (flat panel detector)
- systems use an X-ray absorber material coupled to a thin-film transistor (TFT), complementary metal oxide semiconductor (CMOS), or charge-coupled device (CCD) to form the image.
- indirect capture and direct capture
define CR (conventional radiographic dynamic range)
- the number of recording densities
- more tissue densities on the digital radiograph are seen, giving the appearance of more detail
define spatial resolution
- the amount of detail present in any image
define raster
zig zag motion
define latent image
image that is not visible due to the image not being processed
analog is the same as -
conventional (film screen radiograph)
If the CR is stored in a cassette too long, what happens to the image?
- it disappears
- the longer the electrons are stored, the more energy the electrons lose
- if energy is lost, the low energy electrons will not be stimulated enough to escape the active layer, and information will be lost
true or false: computed radiography is very similar to conventional radiography?
- true
- they both use cassettes to capture the image (latent image)
what is the difference between computed and conventional radiography?
computed:
- digitizes an image
- needs to be processed
- is digitized in the reader
is a PSP system, how do we release the latent image?
- use a laser
for conventional radiography, what impacts magnification?
- OID (object to image distance)`
for direct radiography, what impact magnification?
- OID
- tech is able to adjust it by either zooming in or zooming out
