RDG 306 Radiographic imaging- Lec UG3.pptx

A guide for Radiography students on an introductory notes on basic imaging

1. RADIOGRAPHIC IMAGING 1 PHOTOGRAPHIC FILMS Photographic principle of X-ray film materials and structures X-RAY FILM CASSETTE Structure, Care, and functional test.

2. Photographic principle of X-ray film materials and structures. X-ray film composition X-ray film are made of different layers, this layers include Supercoat (The outer layer) Emulsion layer Adhesive layer Film base

3. Photographic principle of X-ray film materials and structures.

4. Photographic principle of X-ray film materials and structures. Supercoat :- This is the outer layer of an X-ray film, Its a durable protective layer, that protect the sensitive emulsion layer underneath it.

5. Photographic principle of X-ray film materials and structures. 2. Emulsion layer:- This is the radiation and light-sensitive layer of the film. This emulsion layer consist of Silver halide crystals suspended in gelatin . NOTE: This Silver Halide is the material that is sensitive to radiation and light.

6. Photographic principle of X-ray film materials and structures. It is believed that the Silver halide was derived from a combination of Silver bromide ( AgBr ) and Silver iodide ( AgI ). This makes up the emulsion layer of an x-ray film, with Silver bromide ( AgBr ) constituting 90% - 99% of the Silver halide, while Silver iodide ( AgI ) makes up the remaining 1% - 10%

7. Photographic principle of X-ray film materials and structures. In recent time, a new material called the Tabular grain or (T-grain) technology has been used and accepted for the manufacturing x-rays film emulsion. Difference between T-grain and Silver halide Films T-grain films Silver halide films Uses flat silver halide crystals that can be dispersed more evenly in the emulsion layer gelatin . Increase in the speed of recorded detail of radiographs. Uses Random shaped silver halide crystals in the emulsion layer. Slow recording of radiographic details.

8. Photographic principle of X-ray film materials and structures. (A) T-grain (B) Silver halide

9. Photographic principle of X-ray film materials and structures. 3. Adhesive layer:- This is the layer that holds or bind the emulsion layer to the last film layer called the base layer. 4. Base Layer:- This is a polyester material (Plastic), which gives the film its physical stability, so that the film can be handled and processed Usually, Blue dye or tint is added to the base layer, to decrease eye strain when viewing the finished radiograph.

10. Photographic principle of X-ray film materials and structures. Types of Photographic Films Direct-exposure films (non-screen films) Screen films. Direct-exposure films :- This are usually called non-screen films, it has a single emulsion layer that is significantly thicker than that of screen film and requires more exposure (20 -400times more radiation) and development time It is used for intraoral dental radiography.

11. Photographic principle of X-ray film materials and structures. Screen films:- This are films intended to be used with one or two intensifying screens. They are more sensitive to light and less sensitive to X-rays (When compared to direct-exposure films) The emulsion layer is thinner, and requires less exposure and less development time Screen film can have either single or double emulsion layer.

12. Photographic principle of X-ray film materials and structures. Double-emulsion films layers.

13. Photographic principle of X-ray film materials and structures. Difference between Single and Double-emulsion films Single emulsion films Double-emulsion films It has one emulsion layer It is used with a single intensifying screen It is used for duplication and subtraction processes. Also in CT, MRI, Ultrasound, Nuclear medicine, Mammography, and in Laser printing. It has an anticurl or antihalation layer Emulsion are coated on both sides of the base layer It has two Suppercoat layer on top of each emulsion layer. It is used with two intensifying screens Absence of an anticurl or antihalation layer

14. Photographic principle of X-ray film materials and structures. Anticurl / Antihalation layer This is a coloured backing on single emulsion film that prevent film from curling and prevents halation. Halation This refers to an image being recorded on the film by light that has been reflected back to expose the emulsion a second time. This light source comes from the intensifying screen used.

15. X-ray films and image formation The production of an image requires 2 steps, Exposure to radiation. For example light, which activate the emulsion material but produce no visible changes. This exposure creates a latent image.

16. X-ray films and image formation 2. Processing of the exposed film The exposed film is processed in a series of chemical solution that convert the invisible latent image into an image that is visible as different optical densities or shades of gray. The darkness or density of the film increases as the exposure is increased.

17. X-ray films and image formation

18. X-ray films and image formation

19. X-RAY FILM CASSETTE Structure, Care and functional test. Cassette: A film cassette is a container for exposed or un-exposed film. The size and shape of the cassette depends on the film

20. X-RAY FILM CASSETTE

21. X-RAY FILM CASSETTE Structure of the X-ray Cassette A typical X-ray cassette consist of a front and a back, hinged at one side. The front is a shallow box cavity, of which is often called the cassette well , and contains the front intensifying screen and the lead blocker

22. X-RAY FILM CASSETTE

23. X-RAY FILM CASSETTE The back of the cassette form a support for the pressure pad, use for maintaining good film-intensifying screen contact. And may be made of steel or Aluminium, lined with lead ( Pb ) foil. The back intensifying screen adhere to the surface of the pressure pad when loaded and closed.

24. X-RAY FILM CASSETTE Back of an X-ray cassette

25. X-RAY FILM CASSETTE The cassette front is either plastic or metal of low radio-opacity to the photon energies transmitted by the patient. Aluminium (Al) is commonly used. The front should be uniform in thickness and density

26. X-RAY FILM CASSETTE

27. X-RAY FILM CASSETTE Qualities of an X-ray film cassette Its should be light enough for the ease of transportation. Be strong to withstand the considerable mechanical stress and strain through normal handling. Be easy to open and close for the purpose of film loading and unloading

28. X-RAY FILM CASSETTE Qualities of an X-ray film cassette 4.Have rounded corners and edges to avoid injuries. 5. From economic point of view, it should be durable and of low cost.

29. X-RAY FILM CASSETTE Care of X-ray film cassette Avoid rough handling of the cassette Screen out any cassette with radiographic fault, e.g crack in intensifying screen or light leaks Clean the cassette once they are stained in the dark room with developing or fixer chemicals

30. X-RAY FILM CASSETTE Function of an X-ray film cassette It protects the films from exposure to light It protects the films from bending and scratching during use. It contains intensifying screens, keeps film in close contact to the screen during exposure.

31. X-RAY FILM CASSETTE Function test of x-ray film cassette Investigating suspected poor screen film contact in xray cassette. 2. Testing the cassette for light leakage 3. Checking for the relative speed of the intensifying screen in each of the cassette.