Ideal Radiograph Long Essays

Ideal Radiographs Important Notes

• kVp controls the wavelength and penetration power of X-rays.
• Whenever kVp is increased, X-rays of shorter wavelength and high penetration power are produced. They are called hard X-rays.
• Whenever kVp is decreased, X-rays of longer wavelength and the least penetrating power are produced. They are called soft X-rays.

Ideal Radiographs Long Essays

Question 1. Ideal radiograph.
Answer.

Ideal radiograph Definition:

• An ideal radiograph provides a great deal of information, the image exhibits proper density & contrast, has sharp outlines & is of the same shape & size as the object being radiographed

Ideal radiograph Characteristics:

• Visual characteristics:
  • Density:
    • It is the overall blackness or darkness of a dental radiograph
    • If the density is too dark, the film will appear too dark
    • As a result, images cannot be visualized properly
    • A radiograph with correct density enables the radiographer to view black areas, white areas & gray areas

Factors Affecting The Density:

First Degree Factors:

• Milliampere
  • An increase in milliampere results in increased density of the film
• Exposure time
  • If the exposure time is increased, then film density is increased
• Kilovoltage peak [kVp]
  • If kVp increases, then film density increases
  • Density varies directly to the square of the relative kVp
    D ∝ [kVp]²
• Source film distance
  • Density varies inversely to the square of the source film distance
    Density = [kVp]² x mA x s/[S-F distance]²

Second Degree Factors:

• Subject thickness
  • Density decreases in patients with increased subject thickness
• Developmental conditions
  • Overdevelopment of film leads to dark films
• Type of films
  • High-speed films change the density
• Screens
  • Screens require fewer mAs
• Grids
  • Grids require more mAs
• Amount of filtration used
  • Reduction in the use of filtration increases the density
• Fog
  • Results in darkening of film
  • Contrast:
    • It is the difference in the degree of blackness between adjacent areas on a dental radiograph
    • Dental radiographs with very dark areas & with very light areas are said to have ‘high contrast’
    • Depends On The Following:
      • Quality of film
      • Film processing
      • Subject thickness
      • kVp
      • Exposure time
• Geometric characteristics:
  • Sharpness:
    • It is capable of reproducing even the smallest details of the object on a radiograph

Factors:

• Geometric unsharpness:
  • Size of the focal spot
  • Object film distance
  • Target film distance
• Motion unsharpness
  • Patient
  • Tube
  • Film
• Film unsharpness
  • Grain size
  • Emulsion
  • Film thickness
• Fog unsharpness
• Intensifying screens unsharpness

Read And Learn More: Oral Radiology Question and Answers

• Magnification:
  • It refers to the image that appears larger than the actual size of the object

Factors:

• Target film distance:
  • It is determined by the length of the position indicating device [PID]
  • The longer the PID, the more parallel X-rays, therefore less magnification
• Object film distance
  • Less the object film distance, less the magnification
• Use of intensifying screens
  • It increases the film object distance & thus creates a magnification
• Distortion:
  • It is a variation of the actual size & shape of the object
  • Increasing the vertical angulation leads to the shortening of the image
  • Decreasing the vertical angulation leads to the elongation of the image

• Anatomical accuracy of radiographic image:
  • Labial & lingual CEJ should superimposed
  • Buccal & lingual cusps should superimposed
  • The buccal portion should superimposed over the lingual portion of the alveolar bone
  • No superimposition of zygoma
• Adequate coverage of the anatomic region of interest:
  • Proper alignment of the film must be present
  • The proper film should be selected
  • Proper technique should be selected

Ideal Radiographs Short Essays

Question 1. Density
Answer.

Density

• It is the overall blackness or darkness of a dental radiograph
• If the density is too dark, the film will appear too dark
  • As a result, images cannot be visualized properly
  • A radiograph with correct density enables the radiographer to view black areas, white areas & gray areas

Factors Affecting The Density:

First Degree Factors:

• Milliampere
  • An increase in milliampere results in increased density of the film
• Exposure time
  • If the exposure time is increased, then film density is increased
• Kilovoltage peak [kVp]
  • If kVp increases, then film density increases
  • Density varies directly to the square of the relative kVp
    D ∝ [kVp]²
• Source film distance
  • Density varies inversely to the square of the source film distance
    Density = [kVp]² x mA x s/[S-F distance]²

Second Degree Factors:

• Subject thickness
  • Density decreases in patients with increased subject thickness
• Developmental conditions
  • Overdevelopment of film leads to dark films
• Type of films
  • High-speed films change the density
• Screens
  • Screens require fewer mAs
• Grids
  • Grids require more mAs
• Amount of filtration used
  • Reduction in the use of filtration increases the density
• Fog
  • Results in darkening of film

Question 2. Target film distance.
Answer.

Target film distance

• This is determined in the intraoral machine by the length of the position indicating device [PID]
• The longer the PID, the more parallel X-rays from the middle of the beam strike the object rather than the diverging rays from the periphery of the beam
• Therefore there is less magnification
• The shorter the PID, the fewer parallel X-rays from the middle of the beam strike the object and more of the diverging rays from the periphery of the beam strike the object
• Therefore, there is more magnification

Ideal Radiographs Short Answers

Question 1. Density and Contrast.
Answer.

Density and Contrast

• When contrast is altered, is also changed
• However, when the density is altered by itself, there is no change in contrast
• This is because
  • Change in kVp produces a change in contrast and density
  • Change in mA alone does not change the contrast
• Thus if there is a change in contrast, density also changes
• mA is a prime factor in controlling density, but not a controlling factor for contrast
• Therefore a change in mA will produce a change in density but not in contrast

Question 2. Define ideal radiograph.
Answer.

Ideal radiograph

An ideal radiograph provides a great deal of information, the image exhibits proper density & contrast, has sharp outlines, and is of the same shape & size as the object being radiographed

Question 3. Contrast.
Answer.

Contrast

• It is the difference in the degree of blackness between adjacent areas on a dental radiograph
• Dental radiographs with very dark areas & with very light areas are said to have ‘high contrast’

Depends On the Following:

• Quality of film
• Film processing
• Subject thickness
• kVp
• Exposure time

Ideal Radiographs Viva Voce

• Density is in direct proportion to milliamperage and kilo voltage and is inversely proportional to focal spot [target] film distance
• Exposure time is inversely proportional to milliamperage and kVp. It is directly proportional to the square of the focal spot film distance
• The useful range of density for a dental X-ray is 0.3 – 2. Density increases with an increase in film fog
• Magnification = Target – film distance/Object – film distance