Chapter 8 The Four Radiographic Qualities Radiographic Qualities

Radiographic Qualities n There are four distinct qualities in a radiograph that determines the

Detail n Detail is the delineation or demarcation that separates one structure, organ or

Detail n Primary Factor: n Detail is primarily controlled by the size of the

Detail n Secondary Factors: n FAD n PFD n Improper Kv ä (High Kv

Density (MAS) n Density (MAS) is responsible for the blackening effect on your film

Density (MAS) n The greater the percentage of blacks and grays the greater the

Density (MAS) n Primary Factor: n Density is primarily controlled by the milliampere-seconds. The

Density (MAS) n Secondary Factors: n Exposure of the film to scattered rays or

Contrast (Kv) n Contrast (KV) refers to the differences between the black, white and

Contrast (Kv) n Minimal contrast suggests that the shadows will be mostly gray with

Contrast (Kv) Main Factor: n Contrast is primarily controlled by the kilovoltage since it

Contrast (Kv) n The higher the KV, the lower the contrast (less difference in

Contrast (Kv) n n n n Less important factors that may effect contrast: Exposure

Distortion n Distortion is the misrepresentation of an anatomical structure on a radiograph. It

Distortion n Main Factors: n Distortion is primarily controlled by the film-anode distance. The

Distortion n Less important factors that may effect contrast n Improper positioning n Angulation

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Chapter 8 The Four Radiographic Qualities

Radiographic Qualities n There are four distinct qualities in a radiograph that determines the overall quality of the film. n They are: ÊDetail ËDensity ÌContrast ÍDistortion

Detail n 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.

Detail n Primary Factor: n 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.

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

Density (MAS) n 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.

Density (MAS) n 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.

Density (MAS) n Primary Factor: n 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.

Density (MAS) n Secondary Factors: n 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. n n

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

Contrast (Kv) n 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.

Contrast (Kv) Main Factor: n 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. n

Contrast (Kv) n 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 k. V 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 k. V levels often result in grayer film.

Contrast (Kv) n n n n 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

Distortion n 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.

Distortion n Main Factors: n 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. n Another important factor is PFD.

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