Xrayfund

6/9/99

Intensifying Screens

• For Kodak use T-Mat-G (600 speed)or T-Mat-H (1200 speed, grainy appearance b/c too few photons, quanta mottle) film
• For Sterling use Cronex 10T or Cronex 4 film
• For Sterling use UVG & UVL
• For Konica use MGH-SR film
• For AGFA use CURIX Ortho HTG or HTL Plus

Chest Films

• AGFA Opthos H
• Kodak Insight—asymmetrical screen and film (emulsion), gray border that is kept separately, one side pulmonary detail, the other does mediastinal and diaphragmatic detail
• Lanex fine (100 speed), high dose, used for extremity

Cassettes

• Provides support for screens
• Provides light tight environment for film
• Aluminum
• Plastic—Carbon fiber (should in theory lower the dosage, over 70 it losses its usefulness, used for pediatrics today
• Cardboard—in the past, extremity, from the video in the early 1980's, w/o intensifying screens takes 40x's more radiation than 100speed extremity system
• Closures—flat versus bowed up panels, squeezes the air out
• Our full spine cassettes have a piece of felt that blocks light, only works for a while and has to be replaced
• C1 cassettes are used for all other, very good, no light leaks, wear out the hinges and the cassette can not be used any more

K-edge absorption

• All rare earth materials have atomic numbers <tungsten
• Therefore, all K shell EBF are less than tungsten
• This is why rare earth phosphors absorb more photon energy than calcium tungstate
• Use KVP values that exceed the K shell EBF for your screens, usually over 60KVP

Screen care

• Number each cassette outside
• Place same number on screen inside
• Clean w/recommended screen cleaner
• As needed
• On a regular basis, once a month
• Film screen contact, only problem is have old aluminum cassettes, at least twice a year
• The normal life of a screen pair is approximately 7 yrs

Processing

Wetting

• Causes swelling of the emulsion to allow chemical penetration
• Water is the solvent

Development

• Production of a manifest image from the latent image, w/o developing it will remain purple w/no image
• pH basic
• No buffers
• Source of electrons—silver to reduced silver
• Chart from book—make sure to read
• Phenidone—shades of gray, quickly or slowly
• Hydroquinone—produces black, fast or quick
• Glutaraldehyde—emulsion swelling

Gurney Mott Theory

• Ag is + and Br is –
• Electrons are free to migrate w/in the crystal
• Sensitivity speck (silver sulfite) is used to attract free electrons, must be positive during this process to attract electrons
• Photoelectric and Compton interactions free electrons
• Loss of electrons from the halides disrupts crystalline structure
• Electrons are attracted to sensitivity speck
• Silver ions are then attracted to the negatively charged sensitivity speck
• Silver is reduced to elemental silver
• The degree of attraction determines the darkness on the film (the more, the darker)

Fixing

• Removal of unexposed silver from the emulsion (make gray and white areas)
• pH is acid (acetic acid)
• buffers (developing solution is basic and are adding it to an acid solution)
• chemical cocktail
• ammonium thiosulfate—responsible for removing undeveloped silver

• solution becomes heavy w/silver
• can't dump down the drain

Washing

• temperature of the wash water should be about 5F below the developer temperature
• get rid of all developer and fixer that might be stuck on the film

Stop Bath

• termination of development and removal of excess developer from the emulsion
• change the pH (acetic acid and water)
• logan.edu/faculty/guebert

Drying

• removal of water
• prepares film for viewing

Manual vs Automatic Processing

• stainless steel tanks--$500
• refrigerated stainless steel tanks--$3000
• table top automatic processor--$3500

Replacement Chemistry

• every thirty days unless you perform regular sensitometry
• think of processing chemicals like a gallon of milk
• take a sip or drink ½ of the gallon
• heat it to 95degrees every day
• do you want to drink it 45 days later

• add replacement fixer into machine first
• add replacement developer second (silver developed makes the film black)
• add starter solution
• bromine ions in solution to attenuate the strength of the replenishment developer
• added to developer solution in processor when chemicals are changed
• if forgotten properly exposed films will be totally overprocessed and completely black

Optimal Processing Temperature

• determined by the dry-to-drop time
• usually b/w 88degrees and 95degrees for automatic processing
• usually 68degrees F for manual processing

Processing Artifacts

• Pi lines—from rollers in automatic processor rolls
• Emulsion pickoff—chemistry stuck on a roller that takes a piece of the picture every time it hits the film
• Guide shoe marks—rollers get knocked out of balance (cross over guide shoe)

End Material for Midterm