CHAPTER 3 HDR104 RADIOGRAPHIC EQUIPMENT AND IMAGE RECORDING 1 RADIOGRAPHIC FILMS SCHOOL OF MEDICAL IMAGING FACULTY OF HEALTH SCIENCES

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1 HDR104 RADIOGRAPHIC EQUIPMENT AND IMAGE RECORDING 1 CHAPTER 3 RADIOGRAPHIC FILMS PREPARED BY: MR KAMARUL AMIN BIN ABDULLAH SCHOOL OF MEDICAL IMAGING FACULTY OF HEALTH SCIENCES

2 LEARNING OUTCOMES At the end of the lesson, student should be able to:- Describe types of medical imaging films Describe the usage and difference of films Define of monochromatic, orthochromatic and panchromatic Explain the process of identifying emulsion side for a single emulsion film Explain the emulsion formation process and film packing Describe the type of grains in emulsion Explain problems associated with films and methods of overcoming them Explain Quality Assurance (QA) test Compare the relative speed of two films

3 What is X-ray Film? X-ray film is a photographic receptor consisting of photographically active or radiation sensitive emulsion coated on a thin sheet like material. It is responsible to record the physical impression of an object by which we can get detail about the object. 3

4 Classification of the Films MEDICAL X-RAY FILM double-coated single-coated screen type non-screen type screen type non-screen type 1. General radiographic film 1. Dental film 2. Kidney surgery film 3. Radiation monitoring film 1. Mammograp hic film 1. CRT film 2. Copying film 3. Laser film 4. Subtraction film 5. Drystar Flm 6. Dryview film 4

5 Direct Exposure Film Used without intensifying screens. Used mainly for extremities, previously for mammography. Requires times more the exposure dose. The emulsion is thicker than screen film. Renders excellent detail. 5

6 Indirect Exposure Film These films are used in conjunction with pairs of I.S. The latent image being produced mainly by light emission from screen phosphors. A wide range of different films are available both the blue- sensitive and green - sensitive. 6

7 Difference B/W Non Screen & Screen Film CHARACTERISTICS DIRECT EXPOSURE FILM INDIRECT EXPOSURE FILM Exposed with Only by x-rays Mainly by vissible light Used Without Screen With screen Emulsion layer Thick Thin Image formation In deep superficialy Processing time more less Resolution more less Characteristic curve No apparent shoulder region in useful density range Screen artifact no May possible Exposure dose more less Used in Orbit and extremities radiography. Also in Industrial Radiography Shoulder region within useful density range General radiography

8 Type Of Direct Exposure Film 1. Dental Film 2. Kidney Surgery Film 3. Radiation Monitoring Film 4. Industrial Film 8

9 Dental Film 1. Periapical Dental Film: Used for single or group of teeth 2. Occlusal Dental Film: Imaging mandibles or maxillae 3. Bitewing Dental Film: Demonstrating the crown 9

10 Kidney Surgery 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. 10 CM 13 CM FOR RENAL VESSELS 10

11 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. 11

12 Films Used With Cathode Ray Tube OR TV Monitor 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 following modalities: 1. Ultrasound 2. Computerized tomography 3. Magnetic resonance imaging 4. Nuclear medicine 5. Digital subtraction imaging 12

13 Substraction 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. Duplicating 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 a copy. 13

14 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. 14

15 The Dry View Film High quality silver based material coated. The heat /laser light sensitive layer contains silver halide /silver behnate crystal. DRYVIEW Film also a type of laser film having high-resolution, It is infra red sensitive photothermographic film that needs no wet film processor. 15

16 The Drystar Film Direct thermal printing Drystar dry imaging films are designed to produce the highest diagnostic grayscale hardcopies. These images can represent the same "look and feel" as conventional x-ray film. Blue base Maximum optical density > 3.5 Daylight film loading (films are insensitive to light) Shelf life: to be used min. 18 months from packaging date Storage temperature: 5-25 C Relative humidity: 30-60% Extended term storage: minimum 20 years 16

17 Spectral Sensitivity Spectral sensitivity is the range of wavelength of the electromagnetic radiation that the film will respond. PEAK SENSITIVITY is the range of wavelength in which the film will exhibit its highest response CUT-OFF SENSITIVITY is the range of wavelength beyond which the film is no longer sensitive.

18 Types Of Film According To Sensitivity MONOCHROMATIC - blue sensitive films

19 ORTHOCHROMATIC - green sensitive film

20 PANCHROMATIC - sensitive to all colors of the visible spectrum

21 Layers Of Radiographic Film 1. Base 2. Subbing layer (Adhesive) 3. Emulsion layer 4. Supercoat 21

22 Film Construction Double sided emulsion film TOTAL FILM THICKNESS =0.008 INCH 22

23 Single sided emulsion film Anti Halation /non curl backing 23 23

24 Difference b/w Single Coated And Double Coated X-ray Film Characteristic Single coated Double coated Emulsion layer One side Both side Patient Radiation dose More Less Noncurl back layer Present Absent Radiographic detail More Less Average gradient (G) Very less more Parallax effect No yes Contrast Less more

25 Radiographic Film Base Initially X-RAY were taken on glass plates. In 1918 cellulose nitrate bases film replaced glass,but discarded because of highly inflammable. In 1920 cellulose tricetate or safety base was introduced. Polyester base replaced cellulose tricetate in the 1960 s, Now a days POLYETHYLENE TEREPHTHLATE RESIN are used..007 Film Base 25

26 Character of Good Base Material structural support for fragile emulsion low light absorption flexible, thick, & strong processing handling viewbox insertion / removal abuse dimensional stability in processing For archival varying humidity NON -FLAMMABLE 26

27 Function of Base Provide support for emulsion layer. To transmit light. 27

28 Subbing Layer (Adhesive Layer) Also called Adhesive layer or Substratum layer. Made of mixture of gelatin solution and solvent of film base. It keeps emulsion layer and base adhered to each other during coating stage and processing. When dye is added, it counteracts cross over effect. Provides uniform surface over which the emulsion can be coated uniformly. 28

29 Emulsion Layer Emulsion is the heart of radiographic film. The X-RAY or Light from I.S. interact with the emulsion and transfer information to the film. It consists of a very homogeneous mixture of gelatin and silver crystal. In typical emulsion 90 to 99% is AgBr and about 1 to 10% AgI. NOTE: The presence of AgI produce an emulsion of much sensitivity than a pure AgBr emulsion. It also contains traces of sulfur(allylthiourea). Emulsion Layers 29

30 Silver halide in a emulsion is in the form of small crystals. Silver halide crystals may be tabular,globular,polyhedral,or irregular in shape. Crystal size might vary from microns in dimeter with about 6.3 x grains per centimeter of emulsion. 30

31 Grain Technology Globular Grain:spherical in shape and has a bigger volume.use for blue sensitive film. Tabular Grain:Has a table top like structure that provides bigger surface but smaller volume. 31

32 Advantages of Tabular Grain Increased RESOLUTION due to reduction in cross- over. Reduction in silver coating weight. Suitable for 45 s processing. 32

33 Grain Size And Distribution GRAIN SIZE and DISTRIBUTION affects the following: SPEED: The bigger the average grain size, the higher the speed of the film. CONTRAST: Affected by size distribution. The more available in the film, the lower the contrast. GRAININESS: Graininess is the apparent clumping of the crystal as seen on the radiograph. The bigger the crystal,the higher the graininess o f the film. 33

34 Binder A binder is an ingredient used to bind together two or more other materials in mixtures. The common type of a binder which we can use is Gelatin. 34

35 Gelatin Gelatin is used as the suspending medium and binding agent for the silver halide particles. It comes collagen fiber in which primary source are the cartilage, skin and the protein matrix (ossein) of bone of animals. 35

36 Why We Use Gelatin As Binder? It is a medium in which SILVER NITRATE and SODIUM BROMIDE can react and the resulting AgBr get finely and evenly dispersed and remain suspended. In warm state it can be easily spread on the film base. On cooling, it sets firmly on the base as gel. 36

37 Why We Use Gelatin As Binder? It is flexible and does not crack easily on bending. It is optically transparent. Gelatin does not react chemically with the silver halide. It is porous so the processing chemicals can penetrate to the silver halide crystals. Some of the constituents in gelatin enhances the activity of Silver bromide and some act as antifoggant. 37

38 Why We Use Gelatin As Binder? It is the great advantage of the gelatin in which it can set its intermolecular space a/c to the condition of the environment, While processing, gelatin swells up in contact with water, allows processing chemicals to enter the layer and react with the grains of emulsion, & On drying it regains its former state. It is believed that gelatin reduces the tendency of reversal of reaction of Silver bromide after exposure 38

39 Making of The Film Emulsion The light sensitive layer of a film is termed the Emulsion. The preparation of emulsion is carried out in four stages: 1. Emulsification 2. Ripening 3. Washing 4. Digestion 39

40 Emulsification Aqueous solution of Silver nitrate and Potassium bromide is mixed with warm solution of gelatin. AgNO 3 + KBr AgBr + KNO 3 Insoluble Silver bromide (AgBr) remains suspended in viscous gelatin. More rapid process of mixing results small grain size, that results narrow grain size distribution hence there is low graininess & better resolution. Note: More bromide is used to increase the negative charge barrier that helps in development process. 40

41 Ripening Emulsion is placed in certain temperature and more gelatin is mixed. Size of the grains and their even distribution is determined at this stage Slow mixing with long ripening at high temp. => Fast emulsion (with large grains) Rapid mixing with short ripening at low temp. => Slow emulsion (with fine grains) Slow mixing with NH 3 at low temp. => Fast emulsion (with large grains) 41

42 Washing After ripening, emulsion is chilled to form thick gel. This gel is shredded. It is washed with water that remove KNO 3 and excess KBr by diffusion process. 42

43 Digestion Shredded and washed emulsion is re-heated to further increase its sensitivity. Re-heating also make the emulsion liquid and suitable to spread on the film base. 43

44 Supercoat (Overcoat) Protective layer of gelatin Provides sturdiness to unexposed radiographic film. Antistatic Reduces damage from scratches, pressure, or contamination during storage, handling and processing. Supercoating 44

45 Few Additives Preservative Phenol as bacteriocide Silver iodide To extend sensitivity towards blue range. Some dyes may extend Colour sensitivity further Glycerin to make the emulsion pliable Saponin To make the emulsion receptive to the processing chemicals Alcohol To prevent frothing during coating 45

46 Coating The Film Different layers of film are coated on the base material with rollers and squeezers. The film lengths are then passed over chilled rollers so that liquefied gelatinous layers settle and harden. Then The film lengths are hung like festoons in an air conditioned room to dry. Mechanical cutters cut The film lengths in sheets of desirable sizes. 46

47 Anti- Halation Layer Halation : it is a phenomenon characterized by formation of a diffuse image or halo around the proper image. This occurs mainly in the single sided film. 47

48 Methods To Prevent Halation Adding a dye to base Adding a dye to non-curling layer. 48

49 Non-curling Layer Preferred for single sided emulsion film. This layer is not removed during development. 49

50 Adding A Dye To Base These dyes cannot be removed during development. Dye introduced in the base is carefully controlled because it increase the density and may interrupt the transparency of the film. Note-dye used in this should be complementary to the exposing light. e.g.,red dye is used for greeen sensitive film,yellow dye is used for blue sensitive film. 50

51 Cross Over Effect It is a type of halation which occurs when film is used with intensifying screen. Occurs only with double emulsion films and two screens. Light from one screen expands in the form of a cone as it passes through the screen and emulsion where a slightly enlarged, less sharp image is formed. 51

52 Cross Over Effect (Cont d) Special dyes incorporated in the emulsion Colored subbing layer is used. Addition of magenta dye also reduces cross over effect. 52

53 Irradiation It is the sideway scattering of light within the crystal of emulsion. This contributes to unsharpness (blurring) of image. 53

54 How Film Records An Image There are three steps:- 1. Formation of subject contrast (Optical image) 2. Recording of latent image 3. Conversion of latent image into permanent image (processing) 54

55 The Latent Image The latent image is the invisible change in the silver halide crystals. The interaction between the photons and the silver halide crystals produces the latent image or manifest image on the emulsion layer. This interaction is sometimes referred to as the photographic effect. 55

56 Formation Of Subject Contrast Subject contrast:- the variation in intensity of x-ray beam after passing the absorber. Subject contrast depends upon atomic No., density, thickness of absorber and the energy of the x-ray beam. Different intensity of beam react differently with the photographic material of the film. 56

57 Sensitivity Speck The shape and lattice structure of silver halide are not perfect. It causes some imperfection which results in imaging property of crystals. So the sensitivity specks is that low energy centre of the crystal which acts as rest house for the 1º electron and development centre for the 2º electron. 57

58 Sensitivity Speck (Cont d) For the formation of sensitivity specks impurity, usually a Silver-gold Sulfide is introduced by chemical sensitization at or near the surface. 58

59 Sensitivity Speck (Cont d) The image forming x-rays deposit energy by photoelectric interaction with atoms of silver halide crystals. Formation of latent image is given by Gurney-Mott theory 59

60 SILVER HALIDE CRYSTAL Photon Absorption INTERSTITIAL Ag ION - SENSITIVITY SPECK + 6. Ag Ion Migration 2. Electron Trapping Electron Trapping Ag Ion Migration 4. Photon Absorption

61 Producing the Latent Image Radiation interaction releases electrons. Electrons migrate to the sensitivity center. At the sensitivity center, atomic silver is formed by attracting an interstitial silver ion. The process is repeated many times resulting in the build up of silver atoms. The remaining silver halide is converted to silver during processing. The resulting silver grain is formed. Silver halide that is not irradiated remain inactive. The irradiated and non-irradiated silver halide produces the latent image. 61

62 Conversion Of Latent Image Into Visible Image This step is also known as processing. There are 4 steps in this processing: 1. Development 2. Fixing 3. Washing 4. Drying 62

63 Characteristics To Be Considered While Selecting Film: Contrast Speed Crossover Spectral matching Bulk of purchase Time of purchase 63

64 Care And Protection Of Film Films should be protected from:- 1. Physical damage 2. Light 3. High temperature 4. High relative humidity 5. Harmful gases and fumes 6. X-rays and radioactive source 7. Fire and theft 64

65 Resolving Power of Films Ability of a photographic emulsion to record fine details It is expressed as the number of line pairs per millimeter which can be distinguished in the image as separate entities Factors affecting the resolution of an image are Grain size, Processing, Diffusion of light inside the emulsion layer and Modular transfer function 65

66 Line Pairs Per Millimeter A black and a white line make a line pair A test pattern of slits cut on a metal plate with gradual fineness is exposed, processed and evaluated under magnification. Radiographic emulsions show 8 20 LP/mm Photographic Fast emulsions show LP/mm Medium emulsions show LP/mm Slow emulsions show over 1000 LP/mm 66

67 Storage Of Film STORAGE AREAS :- The hospital or x-ray department The dark room The imaging room 67

68 Handling And Storage Of Radiographic Film X-ray film is a sensitive radiation detector and it must be handled in an area free of radiation. Film storage must be shielded. The darkroom adjacent to the x-ray room must be shielded. If film use is low more shielding may be required. 68

69 Handling and Storage of Radiographic Film Improper handling of the film will result in poor image quality due to artifacts. Avoid bending, creasing or otherwise rough handling the film. Avoid sharp objects contacting the film. Hands must be clean and dry. Avoid hand creams, lotions or water free hand cleaners. Static electricity or a dirty processor can cause artifacts. Artifacts must be avoided. 69

70 Handling And Storage Of Radiographic Film Heat and Humidity must be controlled. Film is sensitive to heat and humidity from the time it is manufactured until the time it is viewed. Heat and humidity causes fog or a loss of contrast. Film should be stored at 20º C (68º F). Humidity should be between 40% and 60%. 70

71 Handling And Storage Of Radiographic Film Light will expose the film. Film must be handled and stored in dark. If low level diffuse light exposes the film, fog is increased. Luminous watches, cell phone and darkroom light leaks should be avoided. Bright light causes gross exposure. 71

72 Handling And Storage Of Radiographic Film Shelf life. All film is supplied in boxes with an expiration date. Most film is supplied in boxes of 100 sheets. The oldest film in stock should always be used first. Rotation is important. Expired will loose speed and contrast and have increased fog. 72

73 FILM BIN - STORAGE KAAB (C)

74 KAAB (C)

75 KAAB (C)

76 X-RAY FILMS Standard Sizes Inches 14 X X X X 12 8 X 10 Metric 18cm x 24cm 24cm x 30cm 30cm x 40cm 35cm x 40cm 35cm x 43cm

77 EXAMPLES OF POOR STORAGE AND HANDLING KAAB (C)

78 FILM FOG!!!! Unintended uniform optical density on a radiograph because of x-rays, light, or chemical contamination that reduces contrast & affects density KAAB (C)

79 KAAB (C)

80 POOR SCREEN CONTACT FOAM BACKING HELPS TO PLACE INTENSIFYING SCREENS IN DIRECT CONTACT WITH THE FILM NO GAPS IF GAPS MORE LIGHT CAN BE EMITTED IN SPACE, CAUSING THE IMAGE TO BE OF POOR DETAIL KAAB (C)

81 KAAB (C)

82 KAAB (C)

83 References No. 1 REFERENCES Richard R. Carlton, Arlene McKenna Adler (2005) Principles of Radiographic Imaging, Delmar 2 Bushong, S. C. (2008). Radiologic science for technologists. Canada: Elsevier.