The Four

1
Chapter 8

• The Four
• Radiographic
• Qualities

2
Radiographic Qualities

• There are four distinct qualities in a radiograph
  that determines the overall quality of the film.
• They are
• Detail
• Density
• Contrast
• Distortion

3
Detail

• Detail is the delineation or demarcation that
  separates one structure, organ or tissue from
  another. The size of the focal spot plays a large
  part in the amount of detail seen on film.
  Penumbra is the blurring of the edges of an
  object due to the size of the focal spot.

4
Detail

• Primary Factor
• Detail is primarily controlled by the size of the
  focal spot. The larger the focal spot, the poorer
  the detail the smaller the focal spot, the
  better the detail, again, due to the penumbra
  effect.

5
Detail

• Secondary Factors
• FAD
• PFD
• Improper Kv
• (High Kv Grey film)
• (Low Kv Black/White film)
• FAD and PFD are concerned with distortion but the
  greater the distortion, the poorer the detail.

6
Density (MAS)

• Density (MAS) is responsible for the blackening
  effect on your film and refers to the amount of
  light that will pass through the film when it is
  held before a viewing box. The amount of density
  is directly proportional to the percentage of
  blacks and grays as compared to whites.

7
Density (MAS)

• The greater the percentage of blacks and grays
  the greater the density of your film. If the
  white areas are excessive, density would be
  considered minimal. Proper density suggests just
  the right proportion of blacks, whites and grays
  for the area being radiographed. With proper
  density one would expect to see all the areas of
  the film adequately.

8
Density (MAS)

• Primary Factor
• Density is primarily controlled by the
  milliampere-seconds. The greater the MAS, the
  greater the density the lower the MAS, the less
  dense the film.

9
Density (MAS)

• Secondary Factors
• Exposure of the film to scattered rays or light
• Exposure of the film to fumes, heat or moisture
• Improper FAD. When the distance is changed and
  MAS is not taken into account the density will be
  incorrect.
• Developing Mistakes
• Improper KV.

10
Contrast (Kv)

• Contrast (KV) refers to the differences between
  the black, white and gray shadows that might be
  represented on a radiograph.
• Excessive contrast suggests that the shadows will
  be black and white and little gray (short scale
  contrast).

11
Contrast (Kv)

• Minimal contrast suggests that the shadows will
  be mostly gray with little black or white areas
  (Long scale contrast). With proper contrast there
  is proper distribution of these three shadows.

12
Contrast (Kv)

• Main Factor
• Contrast is primarily controlled by the
  kilovoltage since it is the kilovoltage which
  controls the penetrating power of the x-ray beam,
  that is , what portions of the film will be
  white, what portions gray, what portions black.
  With black shadows there has been complete
  penetration, with gray shadows some penetration
  and with white shadows no penetration.

13
Contrast (Kv)

• The higher the KV, the lower the contrast (less
  difference in adjacent densities) the lower the
  KV, the higher the contrast. Remember that higher
  the kV the more Comptons scattering. This
  scatter, which occurs at the higher energy
  levels, will be strong enough to make its way
  onto the film. This is why higher kV levels often
  result in grayer film.

14
Contrast (Kv)

• Less important factors that may effect contrast
• Exposure of film to scattered rays or light
• Exposure of film to fumes, heat or moisture
• Outdated film
• Improper FAD or Improper MAS
• Developing Mistakes
• Film emulsion characteristics
• Contrast is increased by the use of cassettes
  rather than cardboard holders

15
Distortion

• Distortion is the misrepresentation of an
  anatomical structure on a radiograph. It cannot
  be completely avoided, but it can be minimized.
  To minimize distortion, use a close PFD and a
  long FAD.

16
Distortion

• Main Factors
• Distortion is primarily controlled by the
  film-anode distance. The greater the FAD, the
  less the distortion the shorter the FAD, the
  greater the distortion.
• Another important factor is PFD.

17
Distortion

• Less important factors that may effect contrast
• Improper positioning
• Angulation of the x-ray beam.
• Focal spot size due to magnification