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X-RAY PHYSICS MIDTERM 2 > WEEK 9--IMAGE QUALITY > Flashcards

WEEK 9--IMAGE QUALITY Flashcards

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1
Q

Image Quality

• Is the _______ of the representation of the patient’s anatomy
• An image that accurately represents structure and tissue is identified as a high-­‐quality radiograph
•The most important characteristics of radiographic
quality are:
–Spatial Resolution
–Contrast Resolution
–Noise
–Artifacts

A

exactness

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2
Q

Resolution

• Is the ability to image two separate objects
and visually dis?nguish one from the other.
• _________ __________ is the ability to image
small objects that have high subject contrast.
– Ex: bone-­‐soft tissue interface
• Conventional radiography has excellent spatial
resolution

A

SPATIAL RESOLUTION

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3
Q

RESOLUTION TEST TOOLS

Line pairs/mm – Depicts how well you can see the distinguish two adjacent structures
More lines=more _________

A

detail

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4
Q

Focal Spot

  • ______ x-­‐ray beam width will produce a sharper image.
  • Small focal spot = _______ detail
A

Smaller

Fine

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5
Q

Contrast Resolution

1 • Is the ability to distinguish anatomic structures of ________ subject contrast
–Ex: (liver/spleen) or (gray matter/white matter)

2• Magnetic Resonance Imaging has the _______
contrast resolution
–Computed Tomography is excellent as well
–Radiography is not nearly as good

A

similar

highest

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6
Q

_______ Contrast –Is the product of image receptor contrast and subject contrast

A

Radiographic

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7
Q

Noise
• Borrowed from electrical engineering
• Audio noise = hum or fluUer heard from a stereo
• Video noise = “snow” on a TV
• Radiographic noise = random fluctua?on in the OD of the image.
–Scatter is the principle source of radiographic noise
–Other sources:
• _____________ ______________
• Patient motion
• Parallax

A

QUANTUM MOTTLE

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8
Q

Quantum Mottle

•Contributes to image noise
• An image produced with just a few x-­‐rays will
have ________ quantum motte.
• The use of very ‘high speed’ imaging system will _________ quantum mottle

***Not enough _______ – can create a mottled or grainy image

A

more

increase

PHOTONS

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9
Q

QUANTUM MOTTLE

– With a fast system you’ll get an image, but it will look very _________

– With a slow system you’ll get the same image, but it cost you more and as a result your resolution is very good.

A

pixelated.

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10
Q

SPEED

1.  \_\_\_\_\_\_\_  image  receptors  have:  
–Higher  Noise  
–Lower  spatial  resolution  
–Lower  contrast  resolution  
–Lower  patient  radiation  dose  
2.  \_\_\_\_\_\_\_  image  receptors   have: 
–Lower  Noise  
–Higher  spatial  resolution  
–Higher  contrast  resolution  
–Higher  patient  radiation  dose
A

Fast

Slow

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11
Q

Image Receptor Factors

Characteristic curve (AKA: H&D curve)
–Is used to describe the relationship between OD
and _________ exposure

A

radiation

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12
Q

Image Receptor Speed

The ability of an image receptor to respond to
an x-­‐ray exposure is a measure of its sensitivity and is referred to as the image _____
.

A

Speed

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13
Q

The LATTITUDE of an image receptor is the exposure range over which it responds with diagnostically useful OD.

  • Different image receptors and imaging systems will have different latitudes.
  • Latitude can also be thought of as the margin of error in technical factors.
  • Latitude and contrast are _________ proportional
A

inversely

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14
Q

Patient Motion

• Can  be  voluntary  or  involuntary  
• Best  controlled  by:  
–\_\_\_\_\_\_\_ exposure  times  
–Use  of  careful  instructions  to  the  patient    
–Suspension  of  patient \_\_\_\_\_\_\_\_\_\_\_\_
–Immobilization  devices
A

short

respiration

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15
Q

Artifacts

1 • Any ________ on an image that is NOT caused by proper shadowing of tissue by the primary x-­‐ray beam.

2 • Are undesirable optical densities or blemishes
on a radiograph.

3 • Can be very interesting at times. You become
the detective

What caused that? STUDY SCREEN 32!!!

A

irregularity

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16
Q

Exposure artifacts

  1. Exposure artifacts are generally associated with the manner in which the radiographer conducts the examination:
    –incorrect screen-­‐film matching
    –poor screen-­‐film contact
    –warped cassettes
    –improper positioning of the grid
    –improper patient position/patient motion
    –double exposure
    –incorrect radiographic technique (mAs, kVp, etc.)
  2. These represents the largest cause for repeat exposure!!
A

know this bullshit

17
Q

Exposure Artifacts
3 • _______ ________ is essential for producing
artifact-­‐free images.
4 • Artifacts on or worn by the patient are often
concealed by clothing –ex. surgical hardware and keys, hair, jewelry, patient clothing,
5. ________ exposure –Forgetting to remove and process film before taking another image.
6. Accidentally pressing the button twice for one exposure
7. Lack of contact between film and________ can cause
blurring of the image

A

Patient preparation

Double

cassette

18
Q

Exposure Artifacts

  1. Dust/dirt in imaging plate/cassette
    –Causes areas of ___________ optical density.
    –Can mimic foreign bodies
    –Seen in both digital and film/screen radiograph
  2. Pathology: NOT An Artifact !!!
A

decreased

19
Q

Processing Artifacts

1 • Often caused by pressure.
–Pressure artifacts typically INCREASE OD(_______)
–Scratches or scrapes that remove emulsion appear
as DECREASED OD (___________)
2 • Roller Marks, Pi lines, Dirty rollers, Chemical fog

A

blacker

whiter

20
Q

Processing Artifacts

  1. Guide shoe marks
    –Caused by ________ positioning or springing of guide shoes in turnaround assembly.
  2. Pi Lines –Occur at 3.1416 inch intervals.
    –As a result of 1 inch diameter rollers
A

improper

21
Q

Processing Artifacts

  1. Drops of developer
    –Circular artifacts of increased optical density.
    –As a result of over exposure from the developer
  2. Drops of fixer
    –Circular artifacts of decreased optical fixer
    – As a result of ________ exposure from the fixer.
    (Can also occur with other acidic liquids)
    .
A

under

22
Q

Handling & Storage Artifacts

• Image  fog  
–temperature,  humidity,  radiation,  light  
• Pressure  marks  
–film  being  stacked  improperly  
• Kink  marks  
• Static  
• Hypo  Retention
A

know

23
Q

Handling Artifacts

Scratches from improper handling
–Result in removal of the emulsion layer.
–And areas of ___________ optical density

A

decreased

24
Q

Handling & Storage Artifacts

  1. Discolored film due to hypo (fixer) retention.
  2. Chemicals NOT washed off = Over time will turn film _______
  3. Kink Marks
    –Caused by rough handling of film before _______
    –Characteristic “fingernail-­‐shaped”
    –Artifact of INCREASED optical density. = DARKER!!
    –Kink marks can mimic ___________
A

brown

processing.

fractures

25
Q

Handling & Storage Artifacts

  1. Static electricity
    –Caused by _____ humidity environments and discharge of light from electrical shock.
    –Artifact of INCREASED optical density. = DARKER!!
  2. Light fog
    •This is what happens when _______ leaks into the dark room or into the light-­‐proof cassette.
    •Results in an INCREASE in the optical density = DARKER
A

low

light

X-RAY PHYSICS MIDTERM 2 (4 decks)

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