2. Qualitiesof the Radiograph
• The image on a radiograph must have all of
the same qualities as an image you visually
see – intensity, contrast, noise, sharpness of
detail, magnification and distortion of shape.
3. Visibilityof Detail
• A visible image is completely worthless unless
the information in it is capable of being
recognized. If the image is blurry, or if it’s size
or shape is grossly distorted, we may not be
able to tell what it is, even though it is visible.
4. Sharpnessof Image Detail
• It may be described as the abruptness with
which the edges of a particular object stop.
• Detail describes the sharpness of appearance
of small structures on the radiograph with
adequate detail, even the smallest parts of the
anatomy are visible.
• It is also refers to the structural lines or
borders of tissues in the image and the
amount of blur of the image.
5. Sharpnessof Image Detail
• Factors that generally control the sharpness of
image detail are the geometric factors : focal
spot size, SID, and object-to-image receptor
distance
6. FocalSpot Size
• The term focal spot is normally used to refer to
the area on the x-ray tube anode from which x-
rays are emitted, as seen from the viewpoint of
the film.
• The influence of the focal spot on detail is
confined to image sharpness.
• = the smaller the focal spot, the sharper the
recorded detail. Because the size of the focal spot
is inversely proportional to image sharpness.
7.
8. FocalSpot Size
• Most machines limited to two focal spot sizes.
• Common office focal spots are 1.0 mm for the
small and 2.0 mm for large.
• Highly detailed radiography such as
mammography use micro-focus tubes with 0.1
mm and 0.3 mm focal spot sizes.
9. FocalSpot Size
• Focal spot size has no relation to distortion of
the shape of the image, because it is not
related to alignment or angles.
10. Filtration
• All x-ray beams are affected by the filtration of
the tube. The tube housing provides about 0.5
mm of filtration.
• Additional filtration is added in the collimator
to meet the 2.5 mm of aluminum minimum
filtration required by law.
• 2.5 mm is required for 70 kVp.
11. Filtration
• 3.0 mm is required for at 100 kVp.
• 3.2 mm is required for operations at 120 kVp.
• Most machines now are capable of over 100
kVp operation.
• We have no control on these filters.
13. Radiographic Quality
• Characteristic of radiographic quality:
– Spatial Resolution (Recorded Detail)
– Contrast Resolution (Visibility of Detail)
– Noise (Visibility of Detail)
– Artifacts
14.
15. Spatial Resolution
• 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.
16. 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. Convention radiology is fair to
poor.
17. Noise
• Noise is an undesirable fluctuation in optical
density of the image. Two major types:
– Film Graininess- no control over
– Quantum Mottle- some control over
18. Film Graininess
• Film graininess refers to the distribution in size
and space of the silver halide grains in the film
emulsion.
• Similar to photographic film. 400 ASA film is
more graininess than 100 ASA film.
• Similar to structure mottle that refers to the
size and shape of the phosphors in the
intensifying screens.
19. Quantum Mottle
• Quantum mottle refers to the random nature
of how the x-rays interact with the image
receptor.
• It is the primary form of radiographic noise.
• The use of high mAs and low kVp reduced
quantum mottle.
20. Quantum Mottle
• Very fast screens have higher quantum mottle
because it takes fewer x-rays to make the
image.
21. 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.
22. Film Processing
• Radiographic Quality is
impacted by film
processing parameters.
• The developer must be
at the proper
concentration and at
the correct
temperature.
23. Film Processing
• The film must also
spend the correct
amount of time in the
developer.
• This is the time &
temperature
relationship.
