Week 2 Flashcards
What is the relationship between electromagnetic frequency and wavelength?
Inverse; as wavelength increases, frequency decreases.
What is the relationship between electromagnetic energy and wavelength?
Inverse; as energy increases, wavelength decreases.
How fast do electromagnetic waves travel?
Electromagnetic waves travel at the speed of light.
What is Bremsstrahlung x-rays?
It causes a change in directionality of the electron when it contacts an atom, releasing energy in the form of an x-ray photon.
What are characteristic x-rays?
Characteristic is the 69 keV energy x-ray photon band with a tungsten anode.
What happens when an electron interacts with an atom in characteristic x-rays?
It knocks out an inner or outer shell electron, causing electrons to move shell valencies and release energy to balance system charge.
IN a characteristic x-ray what type of electron loss causes diagnostic level x-rays?
Only the inner shell electron loss causes diagnostic level x-rays.
How much energy deposited by the electron is turned into an x-ray?
Approximately 0.5%.
How is 99.5% of the energy deposited by an electron lost?
Heat.
How does target material affect the x-ray beam?
Higher atomic number results in a better quality x-ray beam.
What effect will doubling the mAs have?
Double the number of x-rays produced; no impact on the quality of the image.
What effect does increasing the kVp have?
Increases the penetration quality of the x-ray beam, demonstrating dense/high atomic tissue on images.
What is coherent scatter?
Coherent scatter is a low energy interaction that excites the atom. When it returns to ground state, it releases a very low energy X-ray photon. The energy is too low to reach the receptor, therefore it does NOT contribute to the image, besides a small amount of noise.
What happens during Compton scatter?
In Compton scatter, a photon interacts with an outer shell electron. When the electron is ionized, the energy of the scatter photon is equivalent to the entering photon energy minus the binding energy of the ejected electron. It can be chaotic and have many interactions.
Why is Compton scatter considered negative?
Compton scatter is considered to be the more negative scatter because of reduced energy, and it is a major factor in reduced image quality (IQ).
What is the photoelectric effect?
The photoelectric effect is similar to Compton scatter but involves the inner shell. Rather than being emitted as a photon, it travels a short distance and is absorbed, contributing to biological changes.
What occurs with the outer shell electron during the photoelectric effect?
The outer shell electron drops to balance the energy, and the energy difference in the valence releases a photon (considered secondary radiation), but this photon lacks energy to reach the receptor.
