Beam restriction device ppt , bmrit course second year

BEAM RESTRICTION DEVICE

1. TRIPURA INSTITUTE OF PARAMEDICAL SCIENCES BMRIT 2nd Year Anirban Bhattacharjee Sourab Basu Nibedita Saha Udit kumar sutradhar Sagarika debnath Rupak shil BEAM RESTRICTION DEVICE

2. BEAM RESTRICTED DEVICE A device that is attached to the opening in the xray tube housing to allow the primary beam to pass through the patient and this device regulate size and shape of xray beam. Reduce scattered radiation Reduce patient dose Improve image contrast

3. PENUMBRA Area of the film that represent the image of an object is called umbra and the area around the umbra is known as penumbra. DEPENDS ON Apparent focal spot ↑ = Penumbra↑ =Image contrast↓ SOD ↑ = Penumbra↓ =Image contrast ↑ OFD↑ = Penumbra ↑ =Image contrast↓

4. TYPES OF BEAM RESTRICTOR DEVICE cone and cylinder collimator

5. APERTURE DIAPHRAGM Simplest type Made up of sheet of lead with a hole at its centre Advantage Simplicity Disadvantage Large penumbra

6. Radiographic image unsharpness using an aperture diaphragm

7. Advantage Modification of the aperture Heavy metal base like lead Better restriction to the xray field Less Penumbra then aperture Round image on a rectangular feild Reduce scattered radiation CONE AND CYLINDER

8. A cylinder (A) is better at limiting unsharpness than a cone (B)

9. COLLIMATOR Collimators is the best xray beam restrictor and it used in linear accelerators used for radiotherapy treatments. They help to shape the beam of radiation emerging from the machine and can limit the maximum field size of a beam. Two sets of shutters moving in opposite pairs Light field provided by light source and mirror mounted at 45degree with in path of beam reflected light source.

10. Beam restrictions process also known as collimation because of this : Collimation↑= field size↓ Volume of area irradiated↓ Scattered radiation↓ Patient dose↓ Image contrast↑ Image quality↑ Density↓ Collimation↓= field size↑ Volume of area irradiated↑ Scattered radiation↑ Patient dose↑ Images contrast↓ Image quality↓ Density↑ COLLIMATION

11. Ultimately, it is the responsibility of the radiographar to use the proper collimation and under no circumstance should exceed the exposure field the size of the image receptor. The radiographer should always limit the field to the part being examined thereby improving the image quality and minimizing the patient dose.