Technical errors Flashcards

1
Q

Processing artifacts are

A

98% of all film artifacts are produced in the processor or by manual processing
This is a review of the majority of the common problems

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2
Q

3 groups of artifacts on film

A

Equipment
Processing
Handling

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3
Q

X-ray tube malfunction

A

Collimator incorrectly positioned
Wrong area of interest
Too tightly collimated causing cut off of area of interest

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4
Q

Table malfunction

A

Grid cut off due to:
Incorrect distance
Incorrect positioning

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5
Q

Cassette issues

A

Front old or damaged
Dirt/debris inside the cassette
Warped cassette
Faulty latches

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6
Q

Foreign body on image can within what part of the machine

A

Within cassette
Within collimator
Between table and grid

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7
Q

Processor artifacts

A

Transport artifacts
Chemical artifacts

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8
Q

Sight development issues

A

Vertical streaks of alternating dark and light areas, as if some liquid ran down the film (which it did!)
The person processing the film did not use a time temperature chart and instead pulled the film out of the developer and held it up to the light to see if the film was black enough
The black streaks are where developer chemical was in contact with the film longer

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9
Q

Handling issues can cause

A

Dust on feed tray
Double exposure
Film fog – from, heat, age etc.
Scatter fog
Static
Sweaty fingerprints
Safelight fog and darkroom integrity

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10
Q

Patient artifacts

A

Motion
Artifacts on haircoat

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11
Q

Technical errors are caused by

A

Improper technique
kVp
mAs

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12
Q

Difference b/w conventional and computed/digital

A

The cassette containing intensifying screens and film is replaced by a reusable imaging plate (IP) or detector
Radiographic images are electronically captured, recorded and viewed at a computer terminal

The “wet” film processor is replaced with a computed imaging reader
After the digital radiographic image is made it is transferred to a computer for “image processing”
The image can then be adjusted as needed by the veterinarian

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13
Q

Computerized radiographic system is and consists of

A

CR was developed to retrofit existing radiographic machines
The basic CR system consists of:
Operator’s console with monitor or touch screen, barcode reader, keyboard and mouse
Variety of plates/cassettes
Plate reader
Conventional x-ray machine and table

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14
Q

Computed radiography steps

A

Enter patient information into the CR workstation
Create a study and ensure all necessary information is entered so the radiographs are legal
Perform erasure on plate(s) to be used
Select view and scan barcode of proper Imaging Plate (IP)
IP is placed in the bucky or on the table
Select proper factors
Make exposure
Insert IP into imaging reader
The image is processed onto a computer monitor
The IP is erased (flashed) so that it can be used again
After the digital radiographic image is made the image can be adjusted as needed by the veterinarian
Accept or reject image after evaluation
Complete study

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15
Q

Imaging plate works by

A

CR uses a PSP (phosphostimulable phosphor) detector screen, called an imaging plate
This type of screen absorbs and stores most of the x-ray energy, which is “read out” later
The PSP screens fit into a cassette that looks very similar to a conventional film-screen cassette; and is used identically to conventional screen-film cassette
Following exposure, the CR cassette is taken to a laser reader unit called an imaging reader
Here the latent image is processed

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16
Q

Image processing in CR after cassette placed in reader

A

The CR cassette is automatically opened and the CR plate is removed
As the CR plate moves through the processor, it is scanned by a laser beam
The laser light stimulates release of trapped x-ray energy stored in the plate as visible light
This released visible light is collected by fiber optics to a photomultiplier tube, producing an electrical signal
The electrical signal is digitized and stored on the computer
The CR plate is then exposed to a bright white light, erasing any residual latent image
The CR plate is returned to the cassette, ejected from the CR reader and ready to reuse

17
Q

Things to note about the CR cassette

A

The latent image formed on CR cassettes is temporary, lasting for about 6-8 hours
Therefore, CR cassettes must be processed in a timely manner, preferably within a few minutes of exposure
Because of their sensitivity to secondary radiation, they must be stored carefully and should be erased (flashed) before use
This is essential if CR plates have not been used for 24 or more
Failure to do so will result in artifacts and reduced detail from background radiation
Scatter, primary beam, light leaks in the cassette or heat
Must tell the image reader what is on the imaging plate before you put it in the imaging reader
Image readers use a different processing algorithm for each different type of image
For example, a lateral tarsus will be processed differently than a DLPaMO metacarpal projection
CR is not faster than conventional processing
Both take about 90 sec to process an image but with conventional processing you can process more than one image during that time frame – CR you cannot*
You still need metal markers – putting them on electronically can make the images invalid in court

18
Q

Advantages of CR

A

No wet processor or chemicals
Improved safety for staff
Better for environment
Short wait for images
The need for retakes is reduced
Images that are too light or dark that would be discarded on radiographic film can be adjusted with the computer software**
Images can be manipulated by computer programs for optimum viewing
They can also be drawn on, measured and annotated
Reduces radiation exposure**

19
Q

Disadvantages of CR

A

Imaging plates are expensive so usually there are only a select few plates that are purchased
Larger plates have lower resistance
They wear out just like regular plates and need replacing
Often noticed by having ghost images on plate
Noise at low levels of radiation
Generally, below 60 kVp
Results in quantum mottle
Still have a processor that requires servicing
Can be a source of artifacts
Need to be flashed before each use due to susceptibility to scatter radiation

20
Q

Digital radiography two types

A

Indirect digital imaging (CCD)
Direct digital imaging

21
Q

Indirect digital imaging is

A

Abreviated CCD
Uses an IP that contains a thin-film transistor (TFT)
Converts radiation to an image that is imprinted on a camera, then transferred to a computer

22
Q

Advantages and disadvantages of CCD

A

Advantages
More sensitive than film
Less expensive than direct digital imaging
Made up of components that can be serviced and replaced
Disadvantages:
An extra step for processing so can result in data loss

23
Q

Direct digital radiography is

A

The conventional radiographic cassette and film are replaced with a digital imaging sensor
This imaging sensor is either permanently affixed to an x-ray table or attached to the DR computer via a cable or Wi-Fi
TFT that picks up the charge and transfers the radiation signal to the digital receptor
Limited by pixel size and how they are wired together

24
Q

Advantages of DR

A

No processing time and immediate image acquisition
Only a few seconds between exposure and image
No imaging plate readers, cassettes, film, or processor and chemicals to hassle with
Excellent image quality
Image can be manipulated to optimize contrast and brightness
Edge enhancement
The computer identifies the edge of a structure

25
Q

Disadvantages of DR

A

More expensive system
Imaging sensor very expensive to replace
Quality is limited by pixels and monitor
Dose creep
Poor technique charts from manufacturer
Hard to identify over exposure because computer fixes images

26
Q

kV and mAs combine to produce

A

kV and mAs combine to produce dose
Every system handles the dose slightly differently
Best to use technique as close as possible to parameters of the animal being radiographed

27
Q

Distance for radiographs causes

A

Distance is typically not a factor in small-animal imaging but is definitely a factor in large-animal imaging
Usually preset in small animal
The x-ray unit must be an exact distance from the detector every time for consistent results

28
Q

Dose on radiographs does what

A

Once digital plate receives dose, computer uses histograms and algorithms to produce image
Plates require certain level of radiation to acquire image
Often means dosing high for smaller body part this issue improves as technology improves

29
Q

Histograms

A

A histogram is a graphic display of an image and is displayed on the software of virtually every digital system

30
Q

Algorithms

A

An algorithm is a formula or set of rules used in calculations or data processing

31
Q

What is done right after a digital unit is purchased and installed

A

When a digital unit is purchased and installed, the service engineer who sets up the computers will establish the veterinarians preference, such as what level of contrast is acceptable in a chest and what density is preferred for abdomens and spines
Once the algorithms for that hospital are established, the service engineer can go into the computer from any location and correct any problems

32
Q

Digital image processing

A

Spatial resolution and contrast resolution
Spatial resolution is expressed in line pairs per millimeter
Contrast resolution is expressed as the values of black and white
The descriptor for contrast resolution is dynamic range
The end result of digital imaging should logically be a high-resolution image
Limited by monitor output and pixel size

33
Q

Contrast and brightness on DP

A

Contrast and brightness (windowing and leveling)
Windowing refers to the contrast range of densities
Leveling refers to density or brightness
Window level establishes the midpoint of the densities visible on the digital image

34
Q

Dynamic range

A

Digital images take advantage of the ability of the digital process to create a greater number of shades of gray in the image
The human eye is not equipped to visualize and appreciate all these features; it is limited to 30 shades of gray
Hence, digital images look much better than film images

35
Q

S-number is

A

used by Fuji, Philips, Konica Minolta
S-number or sensitivity number is the amount of luminescence emitted at 1mA at 80kVp and has a base value of 200
S-numbers are inversely proportional to exposure reaching the IP
S-numbers below the acceptable range indicate the IP was overexposed
S-number above the acceptable range indicate the IP was underexposed
S-numbers can be unpredictable because of the multiple variables involved in the algorithm*

36
Q

Rules for s-number

A

S-numbers below 50% of the lower acceptance range MUST be repeated – there is a possibility that you burnt out a pathology
S-numbers above the upper acceptance range can be passed as long as quantum mottle is not present on the image

37
Q

Digital imaging artifacts are caused by

A

Caused by the IP, grid, software or mechanical system
Identify the cause to correct
Most artifacts are human error
Most common artifact is quantum mottle

38
Q

Picture archiving and communications system

A

Used by both CR and DR
It is the computerized organization and storage of the radiographic images
Must store the information in two places
All computers fail