WEEK 8---Film & Film Processing Flashcards
X-Ray Film
• Film is a media that makes a permanent record of the image.
• Image recorded on film is caused by exposure to __________
photons
X-Ray Film Cross Section
OVERCOAT EMULSION ADHESIVE BASE ADHESIVE EMULSION OVERCOAT
KNOW LAYERS
Film Construction-BASE •Today made of a polyester plastic –Used to be glass •Must be clear, strong, consistent thickness •Tinted pale blue or blue-gray –Reduces eye strain •Coated on 1 or 2 sides with \_\_\_\_\_\_\_\_\_
emulsion
Film Construction-EMULSION
•Film emulsion can be on one side or both sides of base
–(single emulsion or double emulsion)
•Emulsion is the active layer of film
•Emulsion is a ________ containing the film crystals
• Protective overcoat layered on top of emulsion
*Made of mixture of gelatin & silver halide crystals
•Most x-ray film emulsions made of:
–silver _________ (98%)
–silver iodide (2%)
•Photographically active layer
–activated by light & radiation to create image
gelatin
bromide
Light vs Dark Areas On Film
•________ areas:
–silver halide crystals that have been exposed to
photons
•turn to black metallic silver after processing
•_________areas:
–no crystals exposed
•silver halide is washed away with processing
Dark
Light
Film Construction
• Film is manufactured to have specific characteristics of speed, contrast & resolution
• Film is also manufactured to be sensitive to specific colors of light:
– This is known as
________________________
SPECTRAL MATCHING
Image On Film
• Single emulsion = better detail • Double emulsion = slightly less detail –\_\_\_\_\_ \_\_\_\_\_\_\_\_ radiation dose needed •Parallax –With double emulsion an image is created on both emulsions –then superimposed •Results in slight blurring of edges
MUCH LESS
Parallax
An image is created on both emulsions
–then ___________
• Results in slight blurring of edges
superimposed
Film Types X 3
1 •__________-Film
–Most commonly used in diagnostic imaging
–Almost always double emulsion
2 •Direct-Exposure Film
–No screens used = significantly higher patient
radiation dose
3 •Other films for special applications
–Duplication, cineradiography, dental radiography
Screen
Screen -Film has several characteristics to consider:
–contrast, speed, spectral matching and safe light
requirements.
KNOW X 4
Film Contrast
A • Manufactured in multiple levels
1 – ______-contrast film (black-and-white image)
• Smaller crystals of uniform size
2 –________-contrast film (more shades of gray)
•Larger crystals with a wide range of sizes
High
Low
Film Speed •Greater efficiency = less exposure = faster -Standard speed ≈ 100 -200 screen speed is twice as fast • Speeds for \_\_\_\_\_\_\_ work: 200-800 • Speeds for high \_\_\_\_\_\_\_: 50-100
routine
detail
***SO KNOW THAT SLOWER = BETTER DETAIL.
Film Speed Characteristics
1 • Single vs Double emulsion
• Double =________
2 • Size/Concentration of Crystals
• Larger, more concentrated crystals = ________
3 • Thickness of emulsion
• Thicker emulsion = _______
*** Remember that in general, the faster the speed,
the lower the patient radiation dose and the
lower the _____________________.
faster
faster
faster
RESOLUTION
Film Speeds
- _________ speed -reduces patient exposure
- _________ speed -reduces image detail
Faster
Faster
Film Storage
- Clean, dry location, light tight location
- 40-60 % Humidity
KNOW X 6
Film Handling
• Do not bend or crease
• Hands must be clean
• Film is sensitive to ________ and scratches
pressure
X-ray Film Sensitivity • Light • X-rays •Gamma Rays •Gases •Fumes •\_\_\_\_\_\_\_\_\_\_\_\_ •Moisture •Pressure •Static Electricity •Age
HEAT
FILM FOG!!!!
Unintended uniform optical density on a radiograph because of x- rays, light, or chemical contamination that ___________ contrast & affects density.
reduces
Image formation
Information on film BEFORE processing =________ image
Made visible by chemical processing
AFTER proper chemical processing = __________ image
LATENT
manifest
_______ = The term applied to the chemical reactions
that TRANSFORM the latent image into a manifest image.
Processing
Processing
•Film passes through:
1–Developer = Changes the silver ions of exposed crystals into metallic silver (black)
2– Fixer = Stops development and treats the film to prevent ________
3– Wash = H2O
fading
Spectral Sensitivity Or Spectral Matching
Film is designed to be sensitive to the color of light emitted by the intensifying screens
•[Blue–UV] light sensitive film:
–CALCIUM TUNGSTATE screens
•[Green,Yellow-Green] light sensitive film:
–______ ________ screens
RARE EARTH
Film is either blue-sensitive or green-sensitive
- This is known as _____________ film
- In the dark room
a. –green sensitive film MUST use a _____ filter
b. –blue sensitive film can use a red or an amber filter
orthochromatic
red
Cassettes X 3
Cassettes serve 3 important functions:
- Protect film from exposure to light.
- Protect film from bending and scratching during use.
- Contain intensifying screens, keeps film in close contact to screen during exposure
KNOW X 3
Cassette Or Film Holder
The cassette is used to hold the film during examinations. It consist of front and back intensifying screens, and has a _________ backing.
•The cassette is light tight
lead (Pb)
Cassette Features-Front
Exposure side of cassette is the front.
• Made of _________ material–easily penetrated by
x-rays,lightweight metal alloy or plastic material made
of resin.
• Intensifying screen mounted to inside of front.
radiolucent
Cassette Features -Back
• Back made of metal or plastic
• Inside back is a layer of _____ _______
–prevents _______________ that could fog the film
• In front of the foil layer is a layer of padding
–maintains good film/screen contact
• Back intensifying screen mounted on padding
lead foil
BACK SCATTER
Intensifying Screens
• Flat surface coated with fluorescent crystals called
_____________ that glow, giving off light when exposed to x-rays.
• The purpose of intensifying screens is to convert x-ray
photons into_________ photons
• They are called intensifying screens because they greatly intensify the exposure of the film.
• Using intensifying screens is one of the most important patient _______ _________ techniques in radiology.
‘phosphors’
light
radiation reducing
Intensifying Screens Phosphors
• RARE EARTH–(emits _______ light)
–Developed in 1980’s
–Most efficient
–most common in use today
• CALCIUM TUNGSTATE (______ light)
–Older technology
–Not as efficient
green
blue
Intensifying Screens
- The light photons generated in the intensifying screen are emitted by__________ crystals.
- These crystals are significantly _________ than the silver halide crystals in the film
- Use of a screen ________ image sharpness somewhat
- Some examinations requiring extremely fine detail use screens with small crystals.
phosphor
larger
reduces
Intensifying Screens
ADVANTAGES:
- Greatly REDUCED patient exposure
- INCREASE x-ray tube life
DISADVANTAGES:
1. LESS detail than direct exposure
know these
Screen Construction
1 • Polyester plastic base – support layer 2 • Reflective layer – increases screen efficiency by redirecting light headed in other directions 3 • Phosphor layer –active layer –X-ray photons converted into light photons 4 • Protective coating
KNOW THIS BULLSHIT
EX…SEE SLIDE 49
_________ = is when the exposure of the emulsion by light is from the opposite side of the intensifying screen
• This causes increased_______ on the image
***Crossover is reduced by adding a ____ to the base
Crossover
blur
dye
Screen Speed
- A relative number that describes how efficiently x- ray photons are converted into light.
- Ranges from ___ (slow) to______ (fast)
- The use of intensifying screen will increase the speed of an imaging system.
50
1200
Screen Speed
• Greater efficiency = less exposure = faster
- Standard screen speed ≈ 100
- 200 screen speed is twice as fast
• Speeds for routine work: 200–800
• Speeds for high detail: 50–100
• Increasing speed also increases image noise
•Faster speed-REDUCES patient exposure
•Faster speed-REDUCES image detail and INCREASES noise (blurring)
THIS IS A REVIEW OF EARLIER SLIDES
Spatial resolution
The use of intensifying screens_____ spatial resolution compared with direct-exposure radiographs.
• Spatial resolution is expressed by the number of line
pairs per millimeter (lp/mm)
lowers
The ______the lp/mm the smaller the object that can be imaged
- Very fast screens = 7lp/mm
- Fine-detail screens= 15lp/mm
- Direct-exposure screens = 50lp/mm
- The Human eye unaided can detect ≈ 10lp/mm
higher
SCREEN FILM “CONTACT”
SEPERATION BETWEEN THE SCREEN AND FILM PRODUCES ______ SHARPNESS
LESS
***SEE SLIDE 57
Care of Screens
• Image artifacts can appear if screens are
_____________or ______________________
–Dirty screens & screens with small scratches can
leave artifacts
• Screens should be cleaned once each month with
manufacturer’s cleaner with antistatic compounds
DIRTY
DAMAGED
