radiographic film

• radiographic film: Recording medium that converts the x-ray beam into a visible image.
• 1896 GLASS PLATE

  • Very Fragile and breakable however, this kind of material provides the highest resolution that we can have.
  • The films are breaking since too many patients use X-rays and  radiographs and, since it is very fragile, it is not economically wise.
• • 1914 CELLULOSE NITRATE
  • Very Flammable and causes fire in hospitals.
  • Not economically wise, it shortens the archival quality
• • 1924 CELLULOSE TRIACETATE
  • To reduce the flammability, this is not as flammable as nitrate only used for safety purposes but it has low quality of image.
  • film with a “safety base”
• 1950 MYLAR BASE

  • Slightly soft films need to be thick enough to be rigid, not flammable, and lighter in weight compared to the previous mentioned. 
  • not as hard as cellulose nitrate and triacetate
• 1960 POLYESTER

  • We use it until now
  • Made up of Molten Polymer
  • wobbly but the archival quality is great that we can now store films last for more than ten years; also non flammable
• Molten polymer is composed of:

  • DMT: DIMETHYL TEREPHTHALATE
  • ETHYLENE GLYCOL
• ARCHIVAL QUALITY : the permanence of the radiograph. The image does not deteriorate with age but remains in its original state.
• Direct Exposure Film 

  • also called as “non- screen film”
  • quality wise for image
• Characteristics of a Direct Exposure film:

  • high quantity of rad = high mAs
  • High mAs = High Patient Dose
  • Lower Blurring =  High Resolution
• Indirect Exposure Film

  also called as “screen film”

  • produces a diagnostically acceptable image with lower patient dose
• Characteristics of an indirect exposure film:

  lower quantity of rad = lower mAs

  Low mAs = Low Patient Dose

  High Blurring =  Lower Resolution
• 1. Single-Coated Emulsion

  • one side only containing all of the layers of the film (emulsion is layered on one side of the base)
• Examples of single-coated emulsion: Copy or Duplicating Film, Dry transfer Film, Laser Printing
• Disadvantage of single-coated emulsion:

  • It causes Halation (causes blurring because of backscatter radiation)
• 1. Double-Coated Emulsion

  • Commonly used radiographic films nowadays
  • same quantity of layers of the film in upper and lower side (emulsion is layered on either side of the base)
  • We can see the image back-to-back
• Disadvantage of double-coated emulsion:

  • We can’t see it under direct white light illumination, that's why we need to use a negatoscope.
• Monochromatic

  • sensitive to blue light
• Orthochromatic

  • sensitive to blue and green light
• Panchromatic

  • sensitive to all lights
• basic parts of the radiograpic film: base and emulsion
• other parts of the radiographic film: adhesive layer and overcoat/topcoat
• thickness of the radiographic film: 150-300 micrometers
• biggest size of the radiographic film:

  • 35 x 43 cm
  • 14 x 17 inches
• 17 x 28 inches - film size used for skeletal survey specifically the spine
• smallest size of the radiographic film:

  • 13 x 18 cm
  • 5 x 7 inches
• the radiographic film is manufactured in total darkness
• OVERCOAT/ SUPERCOAT

  • A protective covering of gelatin that enclosed the emulsion
  • used to protect the film from scratches and any environmental factors such as your fingerprints
• composition of the overcoat: made up of transparent gelatin
• Purpose of the overcoat:

  • Prevent damage to sensitive emulsion layer
  • Protects the emulsion from scratches, pressure and contamination.
  • Allows rough manipulation of x-ray film before exposure
• thickness of the overcoat: 2-5 micrometer
• EMULSION

  • The heart of the radiographic film
  • Radiation and light sensitive
• the emulsion is the material with which x-rays or light photons from radiographic intensifying screens interact and transfer information
• thickness of the emulsion: 3-5 micrometer
• 2 Principal Components of emulsion: silver halide crystal & gelatin
• the emulsion is the active layer of the film while the silver halide crystal is the active ingredient of the emulsion
• characteristic of the silver halide crystal: high atomic number (Z) - metallic 
• Composition of silver halide crystal:

  • Silver bromide: 98%
  • Silver iodide: 2%
• Silver Halide Crystal Formation:

  I. Crystal Formation:

  • Dissolve metallic silver (Ag) in nitric acid (HNO3) to form silver nitrate (AgNO3).
• Silver Halide Crystal Formation:

  II. Activation (through mixing AgNO3) 

  • Activating using Potassium Bromide (KBr) to form Silver Halide Crystal