1- R/G Quality
It refers to how easily details can be perceived on a radiograph.
We must obtain as much diagnostic information as possible about the internal structures of the patient.
Radiographic quality depends on radiographic density, contrast, and geometric factors that affect detail and definition.
2-Detail
Detail means degree of sharpness or definition of an object on a radiograph.
Detail is good if structural and contour lines of the object are sharp.
Factors:i) Geometric factors
ii) Intensifying screens
iii) Motion of the patient, film and X-ray tube
iv) Differential absorption of X-rays
v) Double emulsion of the film
vi) Radiographic mottle
vii) Exposure factors used
viii) Film processing
ix) Scatter radiation and fog
3-Density
Radiographic density is defined as the degree of blackness, or “darkness,” on a radiograph.
An important concept to remember is that x-rays make radiographic film black.
Black areas on a developed radiograph are produced by deposits of metallic silver in the film emulsion that result from exposure to x-rays and their subsequent processing.
Density is influenced by the quantity and quality of the x-ray beam, as well as the type and thickness of the tissue under examination.
4- Development of chart
A chart based on tissue thickness and anatomic part that can be consulted for predetermined machine settings.
A technique chart prevents the need for second radiographs due to inappropriate exposure factors.
Santes’ rule: Calculation for determining an approximate amount of kilovoltage (kVp) necessary for a given anatomic area on the basis of measurement and the grid being used:
(2×tissue thickness in cm)+source-image distance(FFD)+grid factor = kVp.
Factors:
Speed of screens
Age of screens
Speed of film
Source-image distance (SID) / FFD
Amount of beam filtration
Temperature and time of film processing
Type of grid
The SID/FFD, amount of beam filtration, film processing, and type of grid should remain constant.
The success of a technique chart depends on the radiographer’s willingness to maintain continuity of the variables.
2. Radiographic Quality
• It refers to how easily details can be perceived on a
radiograph.
• We must obtain as much diagnostic information as possible
about the internal structures of the patient.
• Radiographic quality depends on radiographic density,
contrast, and geometric factors that affect detail and
definition.
3. Radiograph of a seashell showing contrast, density, and detail
characteristics.
6. DETAIL
• Detail means degree of sharpness or definition of an object on a
radiograph.
• Detail is good if structural and contour lines of the object are sharp.
7. Following factors influence detail:
i) Geometric factors
ii) Intensifying screens
iii) Motion of the patient, film and X-ray tube
iv) Differential absorption of X-rays
v) Double emulsion of the film
vi) Radiographic mottle
vii) Exposure factors used
viii) Film processing
ix) Scatter radiation and fog
8.
9.
10. RADIOGRAPHIC DENSITY
• Radiographic density is defined as the degree of blackness, or “darkness,” on a
radiograph.
• An important concept to remember is that x-rays make radiographic film black.
• Black areas on a developed radiograph are produced by deposits of metallic
silver in the film emulsion that result from exposure to x-rays and their
subsequent processing.
• Density is influenced by the quantity and quality of the x-ray beam, as well as
the type and thickness of the tissue under examination.
11. Factors Affecting Radiographic Density
Greater radiographic density may be produced by increasing
(1)the total number of x-rays that reach the film
(2) the penetrating power of the x-rays
(3) the developing time
(4) the temperature of the developer.
The radiograph becomes darker as more x-rays reach the film.
12. • Radiographic density is also influenced by the
thickness and type of tissue being radiographed.
• Body parts that have greater thickness absorb more
x-rays, resulting in a lighter image on the radiograph.
• Radiographic density is inversely proportional to
tissue density.
• In other words, if the density or thickness of tissue
doubles, the number of x-rays reaching the film is
approximately halved.
13. These two radiographs have been exposed with the same exposure factors.
A is a VD view of the abdomen of a Saint Bernard.
B is a VD view of the abdomen of a Labrador retriever.
Because of the great difference in size of the Saint Bernard and the
Labrador retriever, there is a marked difference in radiographic
density. A exhibits much less radiographic density than B.
14. Drawing illustrating the influence of tissue density on radiographic
density. Bone tissue is almost twice as dense as soft tissue.
15.
16. Radiographic Contrast
• Radiographic contrast is the density difference between two adjacent
areas on a radiograph.
• When the density difference is great, the radiograph is said to have
high contrast or a short scale of contrast.
• That is, a radiograph with high contrast exhibits many black and white
tones.
• For example, a radiograph with white bone and a black background
has high contrast
17. • Of course, there are extremes in contrast.
• It is not desirable to have a radiograph with too high or too low of contrast .
• A good radiograph should have a suitable range of differentiated radiographic
densities (blacks, whites, and grays) so that the eye can easily see the detail.
Radiograph of a lateral view of a
canine stifle joint showing extremely
high contrast.
18. A, Radiograph of a lateral view of a canine stifle joint showing a short scale of contrast. The
bone tissue of the leg is relatively white compared with the surrounding tissue.
B, Radiograph of a lateral view of a canine stifle joint showing a long scale of contrast. The
entire radiograph—bone and soft tissue—has an overall gray appearance.
25. Technique chart
• A chart based on tissue thickness and anatomic part that can be consulted
for predetermined machine settings.
• A technique chart prevents the need for second radiographs
due to inappropriate exposure factors.
•Santes’ rule: Calculation for determining an approximate amount
of kilovoltage (kVp) necessary for a given anatomic area on the basis of
measurement and the grid being used:
(2×tissue thickness in cm)+source-image distance(FFD)+grid factor = kVp.
26. Factors influence the chart:
•Speed of screens
•Age of screens
•Speed of film
•Source-image distance (SID) / FFD
•Amount of beam filtration
•Temperature and time of film processing
•Type of grid
27. The SID/FFD, amount of beam filtration, film processing, and type of grid
should remain constant.
The success of a technique chart depends on the radiographer’s
willingness to maintain continuity of the variables.
