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IMAGE QUALITY
Radiographic Quality
 Radiographic Quality refers to the fidelity
with which the anatomic structures being
examined are i...
 Characteristic of radiographic quality:
 Spatial Resolution (Recorded Detail)
 Contrast Resolution (Visibility of Deta...
Spatial Resolution
 Resolution is the ability to image two
separate objects and visually
distinguish one from the other.
...
Contrast Resolution
 Contrast resolution is the ability to
distinguish structures with similar subject
contrast such as l...
Noise
 Noise is an undesirable fluctuation in
optical density of the image.
 Lower noise results in a better
radiographi...
Film Graininess
 Film graininess refers to the distribution
in size and space of the silver halide
grains in the film emu...
Quantum Mottle
 Quantum mottle refers to the random nature
by which x-rays interact with the image
receptor.
 Principal ...
Quantum Mottle
 Very fast screens have higher quantum
mottle because it takes fewer x-rays to
make the image.
Speed
 Resolution and noise are intimately
connected with speed.
 While the speed of the images receptor is
not apparent...
Radiographic Quality Rules
 Fast Image receptors have high noise and
low spatial and contrast resolution.
 High spatial ...
Film Factors of Quality
 Characteristic curve
 Density
 Contrast
 Latitude
 Processing
 Time
 Temperature
Sensitometry
 Sensitometry is the study of the
relationship between the intensity of
exposure of the film and the blackne...
Sensitometry
 Two principles involved.
 Exposure of the film
 Amount of light transmitted through the
processed film of...
Characteristic Curve
This relationship is
called the
characteristic curve
or H & D curve of
the film.
H & D stands for
H...
Parts of the Characteristic Curve
Toe and shoulder
low and high ,
exposure levels,
where large
changes in
exposure result...
Parts of the Characteristic Curve
 The straight line or
intermediate area is
where very small
changes in exposure
results...
Log Relative Exposure (LRE)
 X-ray films responds to a
wide range of exposure
from 1 mR to 1000 mR.
 It is not the absol...
Optical Density
 It is not enough to say that OD is the
degree of blackening of a radiograph,or
that a clear area of the ...
Optical Density Range
 The optical density
range is from 0.0 to
4.0 corresponding to
clear and absolute
black repectively...
Fog density and base density
 Most unexposed and processed film has an
OD in the range of 0.1 to 0.3,corresponding to
79%...
Base fog or base density
The tint of the base
of the film and the
inadvertent
exposure of the
during processing.
Range i...
Items that Impact Base Fog
 Film storage
 Film exposure to wrong spectrum of light
or light intensity.
 Chemical contam...
Contrast
The variations in the OD in the
radiograph is called radiographic
contrast.
Marked differences in OD----High
co...
 Radiographic Contrast is the combined
result of image receptor contrast and
subject contrast.
 Image receptor contrast ...
Contrast
 Subject contrast is determined by the size,
shape and x-ray attenuating
characteristics of the subject being
ex...
Image Receptor Contrast
 Inherent to the film and screen
combination but is influenced by:
 Range of Optical Density
 F...
Image Receptor Contrast
The slope of the
straight line portion
of the H & D curve is
the receptor
contrast.
The average
...
Average Gradient
The average
gradient is a straight
line drawn between
0.25 OD and 2.0 OD
above base plus
fog.
This is t...
Speed
Speed is the ability
of the receptor to
respond to low x-ray
exposure.
The H & D curve is
useful in comparing
spee...
Speed
 A relative number of 100 given to Par
Speed Calcium Tungstate Screens.
 High Speed Calcium Tungstate has a
speed ...
Speed
 By knowing the Speed, sometimes
referred to as the Relative Speed Value, it
is easy to convert the technical facto...
LATITUDE
Latitude can be
observed on the H
& D curve.
Latitude refers to
the range of
exposure that will
produce a
diagn...
Latitude
Latitude and
Contrast are
inversely
proportional.
Wide latitude has a
wide gray scale or
low contrast. (B)
Nar...
Latitude
 Latitude is designed into some screen and
film combinations. With wide latitude, the
error factor in technique ...
Film Processing
Radiographic
Quality is impacted
by film processing
parameters.
The developer must
be at the proper
conc...
Film Processing
The film must also
spend the correct
amount of time in
the developer.
This is the time &
temperature
rel...
Processing
 Speed and base fog increase with the
temperature.
 Contrast will increase to a point and then
drop with the ...
THANKS
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Image quality

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x ray Image quality

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  • Excellent collection of radiology presentations mate! Its really nice that in many of these you have used the Textbook of Radiology as the main reference! I am a Radiology resident my self. I much appreciate your work. I would love to get in touch sometime. Regards - Dr Mateen
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Image quality

  1. 1. IMAGE QUALITY
  2. 2. Radiographic Quality  Radiographic Quality refers to the fidelity with which the anatomic structures being examined are imaged on the film.  Three main factors:  Film Factors  Geometric Factors  Subject Factors
  3. 3.  Characteristic of radiographic quality:  Spatial Resolution (Recorded Detail)  Contrast Resolution (Visibility of Detail)  Noise (Visibility of Detail)  Artifacts
  4. 4. Spatial Resolution  Resolution is the ability to image two separate objects and visually distinguish one from the other.  Spatial Resolution is the ability to image small structures that have high subject contrast such as bone-soft tissue interface.  When all of the factors are correct, conventional radiography has excellent spatial resolution.
  5. 5. Contrast Resolution  Contrast resolution is the ability to distinguish structures with similar subject contrast such as liver-spleen, fat-muscle.  Computed tomography and MRI have excellent contrast resolution. Conventional radiography is fair to poor.
  6. 6. Noise  Noise is an undesirable fluctuation in optical density of the image.  Lower noise results in a better radiographic image because it improves contrast resolution.  Two major types:  Film Graininess- no control over  Quantum Mottle- some control over
  7. 7. Film Graininess  Film graininess refers to the distribution in size and space of the silver halide grains in the film emulsion.  Similar to structure mottle that refers to the size and shape of the phosphors in the intensifying screens.  Inherent in image receptor, and are not under the control of technologist, and they contribute very little to radiographic noise.
  8. 8. Quantum Mottle  Quantum mottle refers to the random nature by which x-rays interact with the image receptor.  Principal contributor to radiographic noise.  Image produced with few x rays will have higher QM than image produced with from large number of x rays. use of very fast intensifying screens results in increased QM.  The use of high mAs , low kVp settings and of slow image receptors reduces quantum mottle.
  9. 9. Quantum Mottle  Very fast screens have higher quantum mottle because it takes fewer x-rays to make the image.
  10. 10. Speed  Resolution and noise are intimately connected with speed.  While the speed of the images receptor is not apparent on the image, it influences both resolution and noise.
  11. 11. Radiographic Quality Rules  Fast Image receptors have high noise and low spatial and contrast resolution.  High spatial and contrast resolution require low noise and slow image receptors.  Low noise accompanies slow image receptors with high spatial and contrast resolution.
  12. 12. Film Factors of Quality  Characteristic curve  Density  Contrast  Latitude  Processing  Time  Temperature
  13. 13. Sensitometry  Sensitometry is the study of the relationship between the intensity of exposure of the film and the blackness after the film is processed.  Unexposed film is clear with a blue tint after processing.  Properly exposed film appears with various shades of gray.  Heavily Exposed film is black after processing.
  14. 14. Sensitometry  Two principles involved.  Exposure of the film  Amount of light transmitted through the processed film of optical density.  Used to describe the relationship of radiation exposure and blackness or optical density on the film.
  15. 15. Characteristic Curve This relationship is called the characteristic curve or H & D curve of the film. H & D stands for Hurter and Driffield.
  16. 16. Parts of the Characteristic Curve Toe and shoulder low and high , exposure levels, where large changes in exposure results in small changes in OD.
  17. 17. Parts of the Characteristic Curve  The straight line or intermediate area is where very small changes in exposure results in large changes in density.  This is the important part of the curve in radiography,where properly exposed radiographs appear.
  18. 18. Log Relative Exposure (LRE)  X-ray films responds to a wide range of exposure from 1 mR to 1000 mR.  It is not the absolute exposure that is of interest but rather the change in OD over each exposure interval  Exposure is represented on logarithmic manner(log relative exposurer).
  19. 19. Optical Density  It is not enough to say that OD is the degree of blackening of a radiograph,or that a clear area of the radiograph represent low OD and a black area represent high OD.  OD density has a pre size numeric value that can be calculated if the level of light incident on a processed film(Io)and the level of light transmitted through that film(It) are measured.  OD=log10 Io/It
  20. 20. Optical Density Range  The optical density range is from 0.0 to 4.0 corresponding to clear and absolute black repectively.  Useful range in general radiography is from 0.5 to 2.25.  Image range is 0.5 to 1.25 OD
  21. 21. Fog density and base density  Most unexposed and processed film has an OD in the range of 0.1 to 0.3,corresponding to 79% and 50% transmission, respectively.these ODs of unexposed film are due to base density and fog density.  Base density is inherent in the base of the film and is due to the composite of the base and s the tint added to the base.  Fog density results from development of silver grains that contain no useful information.higher fog density reduces the contrast of the image.
  22. 22. Base fog or base density The tint of the base of the film and the inadvertent exposure of the during processing. Range is from 0.1 to 0.3. Should be never above 0.30 most is .21 OD
  23. 23. Items that Impact Base Fog  Film storage  Film exposure to wrong spectrum of light or light intensity.  Chemical contamination.  Improper processing.  High Base fog levels reduce contrast.
  24. 24. Contrast The variations in the OD in the radiograph is called radiographic contrast. Marked differences in OD----High contrast radiograph. OD differences are small----Low contrast radiograph
  25. 25.  Radiographic Contrast is the combined result of image receptor contrast and subject contrast.  Image receptor contrast refers to the contrast inherent in the film and influenced by the processing of the film.
  26. 26. Contrast  Subject contrast is determined by the size, shape and x-ray attenuating characteristics of the subject being examined and the energy (kVp) of the x- ray beam.
  27. 27. Image Receptor Contrast  Inherent to the film and screen combination but is influenced by:  Range of Optical Density  Film Processing Technique  Film type is determined by the type of intensifying screens used.  Film-screen images always have higher contrast compared with direct exposure images.
  28. 28. Image Receptor Contrast The slope of the straight line portion of the H & D curve is the receptor contrast. The average gradient is a straight line drawn between the densities of 0.25 and 2.00 + base fog.
  29. 29. Average Gradient The average gradient is a straight line drawn between 0.25 OD and 2.0 OD above base plus fog. This is the useful range of optical density in on most radiographs.
  30. 30. Speed Speed is the ability of the receptor to respond to low x-ray exposure. The H & D curve is useful in comparing speed when selecting film or screens.
  31. 31. Speed  A relative number of 100 given to Par Speed Calcium Tungstate Screens.  High Speed Calcium Tungstate has a speed of 200. Half of the exposure is needed to produce the same image.  Rare earth screen film combinations range is speed from 80 to 1600.
  32. 32. Speed  By knowing the Speed, sometimes referred to as the Relative Speed Value, it is easy to convert the technical factors for one speed to another speed.  When image receptors are replaced,a change in mAs setting may be necessary to maintain the same OD,e.g if image receptor speed is doubled, the mAs must be halved.no change is required in kVp.
  33. 33. LATITUDE Latitude can be observed on the H & D curve. Latitude refers to the range of exposure that will produce a diagnostic range OD.
  34. 34. Latitude Latitude and Contrast are inversely proportional. Wide latitude has a wide gray scale or low contrast. (B) Narrow latitude has a short scale or high contrast. (A)
  35. 35. Latitude  Latitude is designed into some screen and film combinations. With wide latitude, the error factor in technique is wider.  Latitude can also be impacted by the technical factors.
  36. 36. Film Processing Radiographic Quality is impacted by film processing parameters. The developer must be at the proper concentration and at the correct temperature.
  37. 37. Film Processing The film must also spend the correct amount of time in the developer. This is the time & temperature relationship.
  38. 38. Processing  Speed and base fog increase with the temperature.  Contrast will increase to a point and then drop with the base fog increase.  Manufactures set processing parameters to optimize speed, contrast and low base fog.
  39. 39. THANKS

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