Chapter 7

Question 1

What are the 5 interactions w/ matter?

Answer 1

-Classical scattering
-Compton scattering
-Photoelectric effect
-Pair production
-Photodisintegration

Question 2

What is classical scattering?

Answer 2

-It is known as coherent or Thomson scattering
-It has low energy generally less than 10keV
-it does not ionize
-its usually absorbed in the body or mostly filtered
-contribute to patient dose

Question 3

What is Compton scattering?

Answer 3

-Occurs throughout diagnostic range
-interacts w/ an outer orbital electron & removes it from its shell
-ionizes matter
-results in image fog
-major source of occupational exposure
-photon energy increases, photon penetrating w/ out interaction increases

Question 4

What is Photoelectric events?

Answer 4

-occurs throughout the diagnostic range between 20kVp - 120kVp
-interacts w/ the inner shell orbital electron
-x-ray photon energy must be equal to or greater than the orbital shell binding energy
-source of patient dose

Question 5

What is pair production?

Answer 5

-occurs when the incident photon has enough energy to escape interaction w/ the orbital electrons
-occurs only w/very high photons of 1.02MeV
-interacts w/ the nucleus of the atom
-two particles are produced: POSITRON
-each particle must have the energy of 0.51MeV

Question 6

What is a positron?

Answer 6

Its an unnatural particle that can cause an annihilation event

Question 7

what is photodidintegration?

Answer 7

-occurs when photons w/ extremely high energy of more than 10 MeV
-it interacts with the nucleus making the atom unstable
-to regain stability, the atom ejects a nuclear particle such as a proton, neutron, electron or an alpha particle
-it is used in radiation therapy

Question 8

what is differential absorption?

Answer 8

-its the difference between x-ray photons that are absorbed photoelectrically versus those that penetrate the body
-higher atomic #, brighter the image
-appears different shades of gray
-air having an atomic # of zero, will appear the darkest

Question 9

What is radiolucent?

Answer 9

Permits the x-ray beams to pass

Question 10

What is radiopaque?

Answer 10

Resists the passage of x-ray beams

Question 11

What is an annihilation event?

Answer 11

is when an electron and a positron interact and both get destroyed. Which is then converted into 2 x-ray photons