CASSETTE, TYPES OF CASSETTE AND INTENSIFYING SCREEN.pptx

Cassette and type

1. CASSETTE, TYPES OF CASSETTE AND INTENSIFYING SCREEN

2. CASSETTE Cassette is a flat, light-tight metal container which is designed to hold the X-ray film and intensifying screen. Cassette is used in conventional and computed radiography for the screen film system and imaging plate respectively

3. CONSTRUCTION OF CASSETTE

4. Cassette consist of front and back hinged at one edge. The front side of the cassette also referred to as Cassette wall. It contains front intensifying screen and short lead blocker used for patient identification. The front side is made up of low atomic number material. Eg : Plastic or Carbon.

5. The front side absorbs only 50% of X-rays compared to aluminium. The back side of the Cassette is made up of high atomic number. Eg:Lead It minimize the back scatter. Thin sheet of lead foil is attached on the backside which is further attached to a plastic foam pad and an intensifying screen

6. FEATURES OF CASSETTE Lightweight to facilitate easy handling and caring. Easy to open and close under low light condition. Uniform contact and between film and screen by the use of foam sponges Availabilty in various types with respect to film size.

7. FUNCTIONS OF CASSETTE Cassette helps to hold intensifying screen and protect them from damage. It exclude all light from entering the Cassette. It maintains a close and uniform contact between the film and screen.

8. TYPES OF CASSETTE Single screen cassette Double screen cassette Curved cassette Gridded cassette Multisection cassette Vaccuum cassette Formatter cassette Angiography cassette Computed radiography cassette

9. SINGLE SCREEN CASSETTE It have a single intensifying screen. These cassettes are designed to be used with single sided emulsion film The principle application of this cassette is mammography

10. DOUBLE SCREEN CASSETTE Double screen cassette have screen both sides It used with double sided emulsion film It is used in general radiogrphy

11. CURVED CASSETE Curved cassette is Internally constructed as conventional cassette with double sided intensifying screen. The shape of the cassette is curved to provide good contact between object and cassette. This cassette is used in panoramic views of mandible (OPG)

12. GRIDDED CASSETTE Gridded cassette have a secondary radiation grid between the front intensifying screen and the front side of cassette. It is used for radiography where conventional bucky system unavailable. Eg:wardradiography

13. MULTISECTION CASSETTE Multisection cassette is designed to hold 3-7 films with their respective intensifying screen and spacers of about 5or10mm in thickness. ADVANTAGE OF USING SPACERS Films which are separated by 5mm spacers will produce images of body sections 5mm apart and like wise 10mm spacers Multisection cassette is used in multiple radiography

14. VACUUM CASSETTE Vacuum cassette is made up of flexible vinyl material. Have a valve,attached at one end. Inside the cassette is removable plastic folder containing single intensifying screen. Single sided emulsion film is inserted inside the folder. The entire fold is placed inside the cassetteand sealed. Vacuum pump is attached to the valve and air expelled thus bringing the intensifying screen and film in close contact It is used in jointradiography

15. FORMATTER CASSETTE Formatter cassette is designed to hold two single sided emulsion films by their edges Also consists of two removable slides whichprotect the film from light exposure when not in use. Do not contain intensifying screens. Formatter cassette is used in CT,MRI,DSA.

16. ANGIOGRAPHY CASSETTE Can hold upto 30 sheets of film size 35*35 cm each positioned with metal spacers. After loading and sliding the two panels the cassette can be inserted into the AOT equipment. Exposed films will have been transferred via exposure areas of AOT apparatus to the take up cassette. A button on the front is pressed closing the sliding lid. Take up cassette then be taken to darkroom and processed.

17. COMPUTED RADIOGRAPHY CASSETTE Imaging plates in place of film and screen. The plates are coated with europium activated by Barium Fluoro Halide. Information is stored in the imaging plates as electrons. Image information is acquired by scanning the plate by laser beam.

18. INTENSIFYING SCREEN

19. What is an intensifying screen? It is a part of cassette which converts xray energy into visible light. It reduces patient dose and also increases the radiographic contrast. Itensifying screen consists of four layers namely BASE REFLECTING LAYER PHOSPHOR PROTECTIVE COAT

20. BASE The base is made up of polyester of 1mm thickness. The base serves as a support on which the reflecting layer, phosphor, protectivelayer are mounted. The base material should be moisture free ,resistance to radiation damage,flexible .

21. REFLECTING LAYER The reflecting layer is in between the phosphor and the base. It is made up of white substance such as titanium dioxide or magnesium oxide. Thickness of 25 Reflects the light towards the phosphor and also increases the efficiency of screen.

22. PHOSPHOR Active layer of screen. Which emits light when exposed by xrays . Thickness of the phosphor 150-300 Commonly used phosphors are calcium tungstate, zinc cadmium sulfide , cesium iodide. Rare earth phosphors are gadolinium oxysulfide,lanthanum oxysulfide,lanthanum oxybromide,yuttrium tantalate. Their absorption and conversion efficiencyis high.

23. PROTECTIVE COAT This is the closest layer of intensifying screen to the film. Considered to be transparent layer. Thickness of layer is 15-25 It is resistant to abrasion and damage caused by handling. Thickness of the intensifying screen is about 1.15-1.3mm.