DENSITY F

• Density


  Number of x-rays
• Amount of exposure from x-rays and light from the intensifying screen


  Determine the amount of blackening after image development
• Density


  General definition of the blackening on the radiograph, result of processing the latent image into a visible image
• Densitometer is used to measure density
• Lung tissue and gas in the intestinal tract attenuate the beam less, appear as darker areas on the radiograph
• Latitude is determined by the range of a given exposure
• Density affected when kVp increases

  More density produced
• Steeper latitude results in higher contrast
• When mass density doubles, x-ray interaction chance doubles
• RADIOGRAPHIC DENSITY is defined as the blackening on the film
• Exposure of film


  The phospors side is in front of the x-ray tube. The film after exposure is latent; processing is required
• Typical exposure for chest x-ray is usually 8 mAs and 79 kVp based on patient thickness
• Presence of density


  Makes the image visible
• Medical radiography and optical density are most used between 0.25 and 2.5 OD. Above 2.5 is overexposed, below 0.25 is underexposed
• Radiograph too dark indicates high OD due to overexposure
• LATITUDE is the range of exposure producing densities between 0.25 and 2.0 above the base plus fog density
• Bones receive less exposure, hence less radiographic density. Bones appear as light areas on the radiograph
• Mass density relates to how tightly atoms are packed
• The opacity of the radiograph is described as the blackening of the film
• If there is no contrast, the image cannot be visualized. Presence of white, dark, or blackness is necessary for contrast. Density and contrast are not related
• Exposure of intensifying screen

  More light is emitted, screen converts x-rays into light
• AVERAGE GRADIENT is used to describe contrast
• Radiographic density is defined as the logarithm (base 10) of the ratio of light hitting the film to the amount of light transmitted through the film
• Higher temperature


  More density produced
• At an OD of 2, only 1% of viewbox light passes through the film
• Interaction of x-rays with tissue is proportional to mass density
• MASS DENSITY is the quantity of matter per unit volume, specified in kg/m3 or g/cm3
• When x-ray interaction is doubled, it is because twice as many electrons are available for interaction
• If the mAs is doubled, the amount of density recorded on the film is doubled
• kVp (kilovoltage peak)


  Changes in kilovoltage can significantly affect density on the film
• mAs (milliampere-seconds)


  The prime factor that controls film density
• Attenuation


  The total reduction in the number of x-rays remaining in an x-ray beam after penetration through a given thickness of tissue
• A 15% increase in kVp, accompanied by a half reduction in mAs, results in the same optical density (OD)
• 1. rays originate from the focal spot area and travel in all directions
• When only a change in density is required to improve a radiograph, the most effective factor is milliampere-seconds
• Even without the Z-related photoelectric effect


  Nearly twice as many x-rays would be absorbed and scattered in bone as in soft tissue
• Absorption process


  An interaction, such as the photoelectric effect, where the x-ray disappears
• The sensitivity specks in the film emulsion will attract more silver ions, resulting in increased blackening on the film
• An increase in kilovoltage peak (kVp) will result in an increase in density recorded on the film
• When kVp is increased, more scatter radiation is produced, adding density to the film