X ray beam rest

Provide tha information about X ray beam restrictors

1. X-RAY BEAM RESTRICTORS BIKASH BHANDARI Bsc.MIT 2 017

2. X-RAY BEAM RESTRICTORS An x-ray beam restrictor is a device that is attached to the opening in the x-ray tube housing to regulate the size and shape of an x-ray beam. Basically,there are three types of beam restrictor devices; 1.Aperature diaphragm 2.Cones and cylinders 3.Collimators

3. Aperature diaphragm Simplest type of X-ray beam restrictor attached to the x-ray tube head. It is basicalllly lead or lead lined metal diaphagm with a hole in the center ,the size and shape of the hole determine the size and shape of the x-ray beam. Principal advantage- simplicity, but produces large penumbra . Lead closed to focal spot. Fixed image receptor size ,Constant SID. The width of the penbra can be reduced by positioning the appratur diaphragm as far away from the x-ray target as possible . Usually possible by attaching the diaphragm to the end of a cone

4. Cones and cylinder Are the modification of aperture diaphragm. In both an extend metal structure restricts the useful beam to the required size. Most commonly used type is cylinder. Difficulty with using cone is alignment. (cone cutting). The flated shape of the cone would seem to be ideal geometric configuration for an x-ray beamrestrictor but flared of cone is greater the flared of x-ray beam.

5. Figure;Aprature(A), diaphragm (B), and cone(c)

6. Collimators Collimators adjust the size and shape of the x-ray field emerging from the tube port. Collimators assembly typically attached to the tube housing at the tube port with swivel joint. It has two advantage's over other types: Has two sets of shutters i.e longittudinal and trnsverse. Sets may actually have two pairs of shutters operating together. The shutters functions as to adjustable Aprature diaphragm provide adjustable rectangular field. Light beam indicate x-ray field.

7. Collimators COLLIMATOR Figure; Alignment of the collimator shutters

8. Collimators generally includes filter and light bulb Fig; alignment of light and x-ray beam

9. X-ray fields is illuminated by light beam from the bulb in the collimator,which is deflected by a mirror mounted in the path of the X ray beam at an angle of 45°. The target of the X ray tube and bulb should be exactly the same distance from the center of the mirror. Have back up system for identifying field size in case the bulb should burn out. Indicated by a calibrated scale on the front of the collimator. Today, positive beam limiting (automatic collimator) are used,which are same as other collimators except that their shutters are motor driven.

10. When casstes is loaded in to the Bucky sensor in the tray sense the cassette size and alignment. Which relay information to the collimator toanupulates the x ray field size.

11. Senses the film size , orientation &SID. Limits x-ray field to size of the film.But it doesn't insure tube &bucket are aligned. PBL must be accurate to with in 2% of the SID Light field and x-ray field aligned so that the sum of the misalignment,along either the length or width of the field,with in 2%of the SID.

12. Testing X-ray Beam and Light beam The alignment of the x-ray beam and light beam should be checked periodically. Equipment; Make an exposurey to mark the position of the X-ray field on the film(40 in.,3.3mAS, 40kVp). Then, enlarge the field size to 12×12in. and expose the film again as same exposure. 4L shaped wires X-RAY film with cassette Small lead letter R

13. Room no.3 Room no. 4 Room no.1

14. Functions Of Restrictors Collimators and others x-ray beam restrictors two basic functions. Decrease off focus radiation. Smaller the x-ray field ,smaller the volume of the patient that is irradiated. Patient protection is principal reason for using collimator. Patient protection Decrease scatter radiation

15. Transmitted photon Field size (cm²) Figure; Transmitted radiation for various sizes of x-ray field Transmitted photon (Arbitrary Units)

16. Reference Christenson's Physics of Diagnostic Radiology Stewart Carlyle Bushong

17. Thank you