Chapter 20: Digital Image Processing Flashcards by Jennifer Gonzalez

Two types of digital radiography systems

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This type of digital radiographer deals with photostimulable imaging plates (PSP, IP)

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This type of digital radiography deals with direct conversion without scintillator and indirect conversion with scintillator

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When were most of the changes made for historical development?

1970s and 1990s
- digital computerization of CT, ultrasound, MRI, Mammo

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Referred to as flat panel detectors (panels)

DR receptors

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What type of digital radiography system does healthcare reimbursement encourage?

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What type of digital radiographer produces a better picture and uses less exposure to the patient, which decreases patient dose?

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No step of light without a scintillator, which captures a better image, requires less steps to get the image. Is directly converted into electrical signal

Direct conversion

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Using light with scintillator can throw artifact. X-ray photons are converted to light photons. and a photodetector (which converts light into an electronic signal)

Indirect conversion

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What is the disadvantage of indirect conversion?

It produces light in all directions which reduces spatial resolution

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What is the type of material inside the CR plate?

Photostimulator phosphor (PSP)

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Are the elements that capture the image and hold it in place for CR? Also holds your laten image

Photostimulator phosphor (PSP)

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When you take an image is run through a processor and it takes 60 seconds for the image to show up?

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Not able to see the image

latent image

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Visualize image you are able to see the image on the computer?

Manifest image

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Is part of the post-processing where you can write on it ( AP, Supine, etc)?

Annotations

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Electrical signals from receptors are converted to what?

Converted to analog format

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Converts an analog signal from the image receptor or detector to a digital signal or language for the computer to manipulate for processing, display, and storage? (converting all that information to a digital picture)

Analog-to-digital conversion (ADC)

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What are considered the binary numbers to be able to create the image?

0 and 1

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How many bits are in 1 byte?

There’s 8 bits in 1 byte

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ADC involves what two distinct steps?

Sampling
Quantification

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Computer memory and power expressed in total bytes

-megabytes, gigabytes, terabyes, etc

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Analog voltage value are measured at a chosen sampling frequency and an analog wavelength

Sampling

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How the image is read

Sampling frequency

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Sampling frequency is associated with what type of digital?

(CR) increase sampling frequency

increase the quality of the image (spatial resolution)

means image sharpness

Spatial resolution

each sample piece now gets a number value and is assigned a binary number of 0 and 1

Quantification

made up of pixels and voxels -field of view (FOV) -spatial resolution dependent on matrix size

Matrix

Picture element

Pixel

volume element - 3 dimentional

Voxel

An arrangement of cells in rows and columns -each cell corresponds to a specific locations in the image

Matrix

-determined by the number of pixels in the rows and columns -expressed by listing the number of pixels in each dimension (length and width) - common sizes: 256x256, 512x512

Matrix size

One individual cell in a matrix - also known as the picture element

Pixel

Three values associated with each pixel:

-two for location (length and width) -one for level of brightness (of shades of gray)

The smaller the pixel

the greater the spatial resolution

what does each pixel contain

bits of information (number of bits per pixel determines the shades of gray demonstrated)

The greater the number of pixels

the greater the image resolution

How many pixels are required to image 1lp/mm

2 pixels

When you increase your matrix and decrease your pixel what happens to your spatial resolution?

Spatial resolution increases

Number of gray shades that a pixel can produce

Bit depth

What is the formula for bit depth

2 to the n power

The higher the 2 to the n power

the more shades of gray there is

What bit depth does most radiography use?

8,10, or 12 bit depth

Determines the size of the area to be imaged / how much of the patient is imaged in the matrix?

Field of View (FOV)

Pixel size=

FOV/Matrix size

Matrix can be changed without affecting what?

The FOV and vice versa

The distance between center of one pixel to center of adjacent pixel

Pixel pitch

The smaller the pixel pitch and pixel size

The better the spatial resolution

The image file size (storage) is affeccted by:

- pixel size - matrix - bit depth

Your matrix, bit depth, look-up table and histogram are all what

Already bulit in

Able to transfer images to different hospitals. Communication between hospitals

Digital Imaging and Communications in Medcine (DICOM)

Has a built in picture perfect image that is comparing to that's why is important to pick the correct body part

Histogram

Gray scale bit depth ranges from what

range from 8 to 32 bits

Is read from left to right white to black

Histogram

Graphic representation of all of the pixel brightness values in the image in the order of their brightness

Histogram

Generated by dividing a scanned area into pixels and determining the signal intensity for each pixel; can be calculated for specific anatomy and procedures.

Histogram

Determines image contrast and the gray scale representation of the tissue - left and right

window width

Determines brightness of an image - up and down ex. think of a window shade, incresed (open) is brighter

window level

-adjustments to image contrast -produces contrast look according to reference contrast scale for exam view

Look-up table (LUT)

What might cause a histogram error

shielding and prosthesis

Considered to be white on in image

shielding, bone, soft tissue and air

under or over exposure conditions compensated for by shifting histogram to align with reference histogram

rescalling

the lower atomic #

the more tranmission to the IR

helps increase contrast

high-pass filtering

enchancing the edges nice and sharp (lip linear)

High-pass filtering

not adjusting to lower technique increasing radiation exposure over time in an attempt to achieve better image quality

Dose creep

making the picture even smoother

low-pass filtering

makes the edges pop out. helps bring out fien details in the image

edge enhancement

changing and switching the colors of an image

inversion

long bone study stiching 2 or 3 images together to make one large picture

stiching

-Densities outside the imaged anatomy -background information -Usually eliminated or will skew the graph

tail or spike in histogram

You want a high signal

low noise

Ability to represent small energy values in data set

Low contrast resolution

The greater the dynamic range

the more shades of gray

How efficient it is in picking up the radiation that is hitting the IR

Detective Quantum Efficiency (DQE)

Measure of how sensitive and accurate incoming data is converted to output viewing

Detective Quantum Efficiency (DQE)

want close to 1 as possible more efficient =less dose to patient

Detective Quantum Efficiency (DQE)

DQE of 1=

100% or no loss of information -higher DQE means lower dose

-provides information about exposure to image receptor -acceptable ranges for best image quality -calculated using histogram values and pixel values of interest mid points -varies between vendors

EI#

calculating how much exposure going on to IR and how much radiation to the pt.

Exposure index (EI)

a comparison between the actual exposure and the proper exposure received by the image detector.

Deviation Index (DI)

determines number of density values -affects density and contrast of system

Pixel Bit depth

-acquired histogram compared to reference histogram -produces consistent image appearance regardless of exposure

histogram rescaling

what color would bone be

high atomic number (white)

What is noise measures as

signal to noise ration -A high SNR indicates little noise in the image. Image noise has an inverse relationship to contrast. Increased noise decreases image contrast

what happens to your density resolution when the gray scale bit depth increases

density resolution increases

-adjusting to image -pre-processing -built in -corrects grays -can enhance pathologies

Look up table

The ability of the imaging system to distinguish between small objects that attenuate the x-ray beam in a similar manner; improves the visibility of the minimum density differences or shades of gray

contrast resolution

increase bit depth

increase contrast resolution

wider window width ( low contrast and long scale)

increase contrast resolution

blur something out in the background

unsharp masking or blurring

Chapter 20: Digital Image Processing Flashcards

(92 cards)