CREED
I solemnly pledge myself before God and to the presence of this assembly, that we may serve humanity with fidelity, honor and objective of the Radiologic Technology profession to the best of one’s ability and render service without any mental reservations to the practice of Radiologic Technology.
Beam- Restricting Devices
Production of Scatter Radiation
There are two kinds of x-rays responsible for the optical density and contrast on a radiograph: those that pass the patient without interaction and those that are scattered in the patient through the Compton interaction.
Remnant x-rays- x-rays that exit the patient.
Image- forming x-rays- those that interact with the image receptor.
Collimation- reduces patient dose and improves contrast resolution.
Primary Factors Influencing the relative intensity of the Scatter Radiation
1. kVp- one of the factor that affect the level of scatter radiation. It is recommended to expose patients in a lowest reasonable kVp to minimize scatter radiation and thus high image contrast radiograph is produced.
2. Field Size- as field size increased, scatter radiation also increases.
3. Patient Thickness- thickness of the body parts determines the amount of scatter radiation, the thicker the part the greater the scatter radiation.
Control of Scatter Radiation
To control the amount of scatter radiation, there are two types of devices are recommended: the beam- restrictors and the grid.
Two Reasons to Restricts x-ray Beam
1. Only the tissue being examined should be exposed.
2. Large x-ray fields result in unnecessary exposure, thus scatter radiation is increased and image contrast is decreased.
Types of Restricting Devices
1. Aperture Diaphragm- the simplest of all the restricting devices. It is basically a lead or a lead- lined metal diaphragm attached to the x-ray tube head. The opening in the diaphragm is usually designed to cover just less than the size of the IR used.
2. Extension Cones and Cylinders- this produces beam in a circular pattern. One difficulty of using cones is the alignment of the x-ray tube, cone and the IR which causes cone cutting; the interference of the cone edge with the x-ray beam.
3. Variable Aperture Diaphragm- the most common beam- restricting device used. This minimizes the amount of off- focus radiation.
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