X-ray interaction with matter

Question 1

What are the 5 different X-ray interactions with matter?

Answer 1

• Classic
• Compton
• Photoelectric
• Pair production
• Photodisintegration

Question 2

What is Classic, coherent/Thompson scattering?

Answer 2

-change in direction of scatter X-rays without any change in energy; X-rays of 10 KeV predominate

Question 3

What is the Compton effect?

Answer 3

-incident photon interacts with outer shell electron which results with ejection of “Compton” or secondary electron

Question 4

What is the equation for Compton scattered X-ray energy?

Answer 4

Compton scattered X-ray energy = incident X-ray photon energy - ejection electron energy

Question 5

What does Compton Scatter do to its energy?

Answer 5

Compton Scatter retains all of its energy and causes more ionizing events before losing all of its energy

Question 6

What happens to Compton Scatter probability when X-ray energy increases?

Answer 6

Compton Scatter probability decreases

Question 7

What happens to Compton’s frequency in comparison to photoelectric frequency?

Answer 7

increases with increase energy of X-photons

Question 8

What is a form of interaction of X-rays when a relatively lower energy photon interacts with the electron in the atom and removes it from its shell

Answer 8

-Photoelectric effect

Question 9

How will the photoelectric effect probability be at maximum?

Answer 9

When the Incident photon’s energy is equal to or just greater than the binding energy of the electron in its shell and when the electron is tightly bound

Question 10

What happens with the Photoelectric effect when the atomic number (Z) of the medium increases? What if the X-ray photon energy increases or doubles?

Answer 10

• Photoelectric effect will increase

- Photoelectric effect will decrease

Question 11

What kind of changes in atomic number (Z) can be responsible for significant change in photoelectric absorption?

Answer 11

-Small changes in Z

Question 12

What is it when an incident x-photon has sufficient energy it may come too closely to interact with the nucleus of the atom. Such interaction will cause x-photon to disappear and in its place a pair of positron(+) and (-) charged electron are produced by the nucleus

Answer 12

Pair-Production

Question 13

How many MeV is required for Pair-Production

Answer 13

1 million MeV

Question 14

What is it when x-photons possess energies above approx 10 MeV. They will escape any interaction with the electrons and be completely absorbed (disintegrated) by the nucleus.

Answer 14

Photodisintegration

Question 15

What is differential absorption a composite of?

Answer 15

X-ray transmission, Compton Scatter, and Photoelectric effect

Question 16

In regards to differential absorption what happens to Compton, PE, and X-ray transmission when X-ray energy increases? Atomic Number? Tissue mass density?

Answer 16

• X-Ray energy increases: decrease in Compton and PE
• Atomic # increases: Increase PE, decrease X-ray transmission
• Tissue mass density increases: proportional increase in Compton and PE, proportional decrease in X-ray transmission