Flashcards in Scatter Radiation Study Guide Deck (78)
What characteristics are important to image quality?
contrast and contrast resolution
What is contrast?
differences of light and dark on an x-ray image
What is the number of shades of gray on an image?
scale of contrast
The ability to image adjacent similiar tissues is defined as?
What three factors contribute to the production of scatter radiation?
increased x-ray field size
increased patient thickness
What is designed to minimize the production of scatter by limiting field size to only the anatomy of interest?
Beam restricting devices
The three principle types of beam restricting devices are?
aperture diaphragms, cone or cylinders and collimators
What two types of x-rays are responsible for Optical Density and contrast on an image?
1. those that pass through the patient without interacting (transmitted)
2. those that are compton scatter within the patient
Define Remnant x-rays:
x-rays that exit the patient
Define Image forming x-rays:
x-rays that exit and interact with the image receptor
What does collimation do?
reduces patient dose and improves contrast resolution
As scatter radiation increases what happens to the image?
it loses contrast and becomes gray/dull
If kVp increases what happens to relative amount of scatter?
If kVp decreases what happens to patient dose?
As the thickness of the patient increases what happens to the probability of scatter?
One way to reduce the production of scatter is by imaging a thinner part by using?
constriction bands or compression paddles
If radiation field size increases what happens to the tissue being irradiated? Amount of scatter being produced?
What device helps to minimize the amount of scatter produced?
What device helps clean up the scatter that has been produced?
What type of beam restricting device is the simplest one that consists of a lead plate with a hole cut in it. The size of the opening determines the field size?
X-rays being produced on other parts of the anode than the focal spot is called?
off- focus x-rays
What x-rays increase blur in the image?
off focus x-rays
What does positive beam limitation do?
automatically collimates to the size of the IR used.
Under NO circumstance should the x-ray beam?
exceed the size of the IR
When the beam is restricted the technique should? why?
increase to compensate for the loss of x-rays in the beam reaching the IR
Removing scatter does what to the optical density?
decreases which makes the image lighter therefore mAs must increase
What is designed to transmit only x-rays whose direction is on a straight line to the IR?