interactions of ionizing radiation

what 3 things can X or Y rays impinging on a material may be

transmission, scatter, absorption

what is primary radiation

radiation transmitted through a material without interaction

what is secondary radiation

radiation scattered in the material

what is ionization

removal of an orbital electron that leaves the atom positively charged

what does ionization result in

ion pair

what charge is the stripped electron in ionization

negative ion

what is the charge of the residual atom in ionization

positive ion

what two things that are uncharged particles are indirectly ionizing radiation

neutrons and photons

the term analogous to half-life is the _

half value layer

what is the half value layer

material that cuts beam in half

what is the unit of the linear attenuation coefficient

cm^-1 or cm or 1/cm

why does it depend on the energy of the photons and the nature of the material

it is the percent of intensity lost per unit thickness crossed

what makes up the combination of attenuation

absorption and scatter

what does the overall process of attenuation result from

several different physical interactions of photons with atoms

what happens to the photons that are not interacted with

they are transmitted

what are other names for coherent interactions

classical, thompston, rayleigh

list what happens in a coherent interactions

an incoming photon interacts with an outer shell electron. the photon gets absorbed by the electron. an identical photon ejects, but not the same one

does the outgoing photon lose energy in a coherent interaction

no

who figured out the photoelectric effect

einstein

what is the cascade effect

each electron fills in and makes characteristic radiation

what interaction has the cascade effect

photoelectric

what is characteristic radiation

when there is a vacancy left in the K shell, so the L shell fills the hole and it releases waves of energy

describe what happens in the photoelectric interaction

a photon interacts with an inner shell electron and it has enough energy to overcome the binding energy to overcome k shell electrons and release a photo electron

what is ejected from photoelectric interactions

photo electron

explain the compton interaction

incoming photon interacts with an outer shell electron. it has enough energy to kick out electron

what is released during the compton interaction

scattered photon and a compton electron

what is different about the scattered photon in the compton interaction compared to the incident electron

it has a longer wavelength and it loses energy and frequency

in coherent scattering, describe the photon that is ejected

different direction, same energy

coherent scattering is _ for high-energy photons interacting in relatively low Z tissues, such as those in the body

nonfactor

what percent of photoelectric interactions involve the K shell

80%

how is the ejected electron in the photoelectric effect ejected

kinetic energy

what two things is photoelectric dependent on

photon energy and the atomic number Z for the absorbing material

where can the scattered xrays be deflected in compton scatter

any direction

what is back scatter

when xrays are scattered back in the direction of the beam

what does some MPs refer to 

peak scatter factor

what is the Zeff of muscle or water

7.4 for all

what does the incoming photon in pair production have

1.02Mev

what does the photon interact so strongly with in pair production

EM field of an atomic nucleus

where does all the energy go in pair production

it is given up by creating a pair of electrons (negative and positive)

what direction do the particles from pair production emitted to

forward

what interaction is an example of energy being converted to mass

pair production

when does the reverse process take place

when a positron combines with an electron to produce two photons

what is annihilation radiation

when two photons are created from reverse process

t/f: pair production is a significant interaction in diagnostic radiology

false

what percent of all pair production event occur near an electron

10%

what happens to the positron that is created from pair production

loses its energy as it cross matter

what does the positron combine with 

one of the free electrons in its vicinity

what happens next once the positron combines with one of the electrons

converts the particles into two annihilation photons

how much energy do each annihilation photons have

0.51Mev

what direction do the photons in pair production get ejected to

opposite directions

PET operates based on the detection of _

annihilation radiation

when does photodisintegration occur

when photons have enough energy to eject a nuclear particle when they are absorbed by a nucleus