X-ray films

1. X-RAY FILMS
Mamita Sakhakarmi
B.Sc. MIT (4th
Batch)
4th
year
Chitwan Medical College

2. Objectives
• Historical background of X-ray film and its
construction.
• Duplitized/Single X-ray film with its
advantage and disadvantage.
• Explain film for medical imaging.
•

3. CONSTRUCTION OF A MEDICAL X-RAY
FILM
• ADHESIVE (Substratum)
LAYER
– Thin coat of gelatin
• EMULSION
– Silver halide crystal in
gelatin binder
• SUPERCOAT
– Hardened gelatin

4. History of film base
• 1st
x-ray film base is glass plate by using roentgen
original film base.
• 1917 – cellulose nitrate film base is widely adopted
but flammable
• 1923 – cellulose triacetate ‘safe film base’- kodak.
• 1932 – Blue tint is added x-ray film
• 1960 – polyester base film – ‘Dupont’ – as cellular
triacetate but it is more resistant (polyethylene
terephthalate )

5. Characteristic of base
• Transparent
• Flexible
• Untreatable
• Uniform thickness & colour
• Impermeable in water & processing solution
• Non inflammable
• Chemically inactive
• Dimensionally stable throughout processing.
• Thickness- 150-300µm

6. Function of base
• Functions of film base
1. To provide support for emulsion layer.
2. To transmit light to view image

7. Adhesive layer
• Preparation used is gelatin solution and solvent of
film base.
• Colour dyes may be used sometimes to prevent
crossover or transmission effect
• Ensures that emulsion adheres to base during
manufacture and processing.

8. Emulsion
• Microscopic crystals of silver-bromide &
silver iodide suspended in gelatin.
• Gelatin – treated with mustard oil
1. Improves sensitivity
2. Keeps silver halides uniformly dispersed
3. Readily penetrated by processing chemical and
water

9. Super-coat
• Thin layer of clear gelatin.
• Emulsion
1. Anti-abrasive layer
2. Provide suitable surface characteristics

10. Types of films
1. Duplitized emulsion films
a. Direct exposure (non-screen films)
 Dental films
1. Periapical
2. Occlusal
3. Bitewing
 Kidney surgery films
 Radiation monitoring films
a. Screen type films
• Monochromatic/ Orthochromatic films

11. Duplitized films

12. Duplitized films
• Advantages
1. Increased sensitivity
2. Increase image contrast
3. Low machine load
4. Low radiation dose to staff and patients
5. No curling effect

13. Duplitized films
• Disadvantages
1. Loss of image quality
a. Crossover effect
b. Parallax effect
2. Economic reasons

14. Dental films
• Periapical Film: 31 x 41 mm for single or group of Teeth
• Occlusal Film: 57 x 76 mm film - mandibles or maxillae
• Bitewing film: 31 x 41 - Demonstrating the crown

15. Kidney film
• This duplitized film non screen film is designed to
enable to radiographic exposure of kidney .
• Each packet contains two films ,one with a fast
emulsion, the other slow.

16. Radiation Monitoring Film
• Similar to the dental film in appearance but very
important.
• Different one side of the base is high speed of
emulsion and another for wide used of exposure level
to be recorded.

17. Screen Type Film
• Pair intensifying screen
• The lateral image being produce by light emission
from the screen and phosphor.
• Wide range of different manufactures film are
available.
1)Blue light sensitive- monochromatic
2) Green light sensitive – orthochromatic

18. Single emulsion film
1. Screen type –
a. Mammography
2. Non-screen type
a. Photofluorography type – cine films
b. Cathode ray tube (CRT) type –
 USG, CT, MRI, DSA, Nuclear Medicine
a. Duplication films – copy radiograph
b. Subtraction films
c. Polaroid films – Old USG films
d. Laser imaging films

19. Single emulsion film
• To help identify the
emulsion side of single
coated film in darkroom,
the manufacturer cuts a
small notch into one
edge of each film

20. Single emulsion film
• Advantages
1. Good image quality
2. Less expensive
• Disadvantages
1. Curling problem

21. FILM FORMATS AND PACKAGING
• Standard Sizes
– 8x10 in.
– 10x12
– 11x14
– 14x14
– 14x17
Other Sizes
 8x12 in.
 12x14
 4x4
 70 mm roll/sheet film
 35 mm roll film
Packaging
 Available in 25 50, 100, and 500 sheets
 AFW (Alternate folded wrapped)
 NIF ( non-interleaved films)

22. Screen type film
• Used in conjunction with a cassette fitted with
a single intensifying screen.
• Particular application mammography.
• The film speed is medium to high contrast.
• It is capable of demonstrating micro
calcification in soft tissue.

23. Non-screen type film
a) Photofluorography film: cine film, roll film
These are films used to record the image produce at
i)The output phosphor of an image intensifier tube.
ii) The fluorescent screen of a camera system.

24. b) Cathode ray tube (CRT)
• These films are used with cathode ray tube camera
and multi-formatter.
• The emulsions are orthochromatic of medium to
high contrast and made to match a wide variety of
CRT phosphor.
• The film sizes commonly used are 8” x 10”, 11”x14”
and 14”x17” .
• Used in- USG, CT, MRI, Nuclear medicine, Digital
subtraction imaging

25. c) Subtraction film
 A type of single emulsion film used with
angiography
 One type prepares a positive copy of the image
 The other type enhances subject contrast and
detail
d) Duplication film
 It is used to duplicate the pre-existing film.
 Duplicating film is a single emulsion film that is
exposed to ultraviolet light or Visible light through
existing radiograph to produce copy.

26. e) Polaroid film
• It is made up of positive and negative film sheets
with a pod of jellified processing chemistry.
• Used particularly in ultrasound imaging.
• The latent image is formed in the silver halide
emulsion of the negative sheet. And the positive
image formed due to migration of Ag ions from the
negative sheet.

27. f) Laser film
• A laser printer uses digital electronic signal from an
imaging device.
• It is high-contrast single-emulsion film with
extremely fine grain, also known as IR film.
• Laser film is a silver halide film sensitized red light
(Panchromatic) or laser light, e.g., HN Laser Film, IR
Laser Film.

28. Non-curl backing
• Present in single sided emulsion
films only.
• As emulsion swells during
processing film tends to curl.
• Prevented by adding subbing
and gelatin layer on opposite
side of emulsion

29. Halation ?
• The ghost image produced out side the proper image,
by the light transmitted through the base and reflected
back from the base-air interface is called halation.

30. Anti-halation layer
• Depending upon angle at which the light strikes it may
– Pass completely out of base.
– Get reflected back producing halo around the proper image.
• Halation causes un-sharpness of image.
• Methods to prevent Halation
1. Adding dye to non-curl backing
2. Adding dye to base

31. Anti-halation layer
• When a colour dye is added to the anti-curl
layer to prevent the effect of halation, it is
called an anti-halation layer

32. Halation
Light from screen
emulsion
base
True image
Halation

33. Crossover effect
• Type of halation occurring in films used with
intensifying screens.
• Prevented by adding dye which effectively
absorbs incident light e.g. Magenta dye in
Kodak x-ray films.
• Dye is removed during processing.

34. Crossover effect

35. Irradiation
• Sideways scattering of light within the emulsion
due to striking of light on halides present in
emulsion.
• Causes un-sharpness of image.
• Can be prevented by thinly coated emulsion.

36. Irradiation
• This is the sideways scattering of light within the
emulsion itself as a result of the light striking the
grains of silver halide
• This light contributes nothing to the image proper but
becomes a source of image unsharpness.
• The use of thin emulsion layers produce less
irradiation.

37. Parallax Effect
• When double emulsion film exposure light the image
is formed in different position same object.
• More common in double emulsion film.