Ch 12 - X-Ray Interactions

Front 1

Target interactions occur between ...

Back 1

with incident electrons interacting with the anode target creating a photon as part of the primary beam

Front 2

what are the two types of target interactions?

Back 2

bremsstrahlung and characteristic interactions

Front 3

electrons are drawn as ...

Back 3

lines

Front 4

photons are drawn as ...

Back 4

waves

Front 5

define attenuation

Back 5

when x-ray photons pass through matter, the beam undergoes a reduction in the number of photons and subsequent loss of energy

Front 6

what percentage of photons are attenutated? what percent actually hits the IR?

Back 6

99.27%

.73% hit IR

Front 7

True/False:

the higher the atomic number the less energy required to remove a k-shell energy

Back 7

false.

the higher the atomic number the HIGHER energy required

Front 8

what is the mass #

Back 8

protons and neutrons

Front 9

what is the atomic number?

Back 9

protons

Front 10

What shell has the highest binding energy

Back 10

k shell

Front 11

Define scattering

Back 11

x-ray photons can interact and change directions

Front 12

x-ray photons can interact and change directions is termed as

Back 12

scattering

Front 13

x-ray photons can interact and transfer ALL the energy to the matter is termed as

Back 13

absorption

Front 14

define absorption

Back 14

x-ray photons can interact and transfer ALL the energy to the matter

Front 15

What are the 5 interactions between x-rays and matter?

Back 15

photoelectric absorption

coherent scattering

compton scattering

pair production

photodisintegration

Front 16

which interactions do we use for x-ray

Back 16

photoelectric absorption

compton scattering

Front 17

what is photoelectric absorption

Back 17

similar to characteristic interactions

..

result of a photon interacting with an inner-shell e-

e- ejected = ionized, positive charge

Front 18

when is photoelectric absorption most likely to occur?

Back 18

when the incident photon has slightly more energy than the binding energy of the inner shell electron

Front 19

ionized atom + ejected e- is called ...

Back 19

photoelectron

Front 20

True/False:
Photoelectrons can travel far within tissue

Back 20

false.

usually absorbed within 1-2 mm of tissue

Front 21

what happens after e- is ejected in the photoelectric absorption

Back 21

characteristic cascade.

when electron drops from outer shell into the opening and releases excess energy in the form of a ..

chacteristic photon which is also called ..

secondary radiation

Front 22

what is secondary radiation

Back 22

primary radiationw hen created from target ineractions, secondary when its created outside of the target.

Front 23

what are the 3 basic rules for the possibliity of photoelectric absorption?

Back 23

1. incident x-ray photon energy must be greter than the binding energy of the inner-shell electron

2. a photoelectric interaction is more likely to occur when the xray photon energy and the electron binding energies are near to one another

3. a photoelectric interaction is more likely to occur with an electron that is more tightly bound in its orbit.

... higher atomic number higher binding energy

Front 24

what is coherent scattering

Back 24

occurs between very low energy photons and matter.

Front 25

what happens in coherent scattering.

Back 25

phtoon interacts with 1 or all the electrons in atom. electrons vibrate at same frequency as the photon.

excited atom immediately releases the excess energy as a secondary photon.

this secondary photon has the same energy and wavelength as the incident photon but travels in a different direction.

Front 26

true/false

there is no transferring of energy occuring during coherent scattering

Back 26

true

Front 27

why dont we use coherent scattering in diagnostic xray

Back 27

energy is too low

Front 28

what is compton scattering?

Back 28

results when xray photon interacts with an outer shell

Front 29

what happens during the compton scattering interaction

Back 29

incident photon interacts with loosely bound outer shell electron, removing it from its shell.

this free electron is called a compton or recoil electron

incident photon continues in a different direction as a scatter photon

Front 30

what is the free electron called in the compton scattering?

Back 30

recoil or compton

Front 31

true/false:

compton scattering

the scattered photon has less energy than the incident photon had, but retains a majority of it

Back 31

true ..

loose bond so it didnt take much energy to remove

Front 32

what is the angle of deflection and which interaction does it pertain to?

Back 32

compton scattering

how deflected will depend on how much loss of energy.

Front 33

angle of deflection:

deflection on 0 degrees = how much energy loss

Back 33

no loss of energy. photon continues in same dirction

Front 34

angle of deflection:

angle increases = how much energy loss

Back 34

more engery is given up to recoil e- and less energy remains with scattered photon

Front 35

what is it called when the photon deflects back towards the source

Back 35

backscatter radiation

Front 36

comtpon photons contain enough energy to do what

Back 36

create biologic damage to tissues

image quality

scatter photons add unwanted exposure to IR

Front 37

what is radiation fog?

Back 37

scatter photons adding unwanted exposure to IR

Front 38

what is used to absorb these phtons and remove the excess before it gets to the IR

Back 38

grids

Front 39

what is pair production?

Back 39

energy of the xray photons is converted to matter in the form of two electrons

Front 40

why dont we use pair production for diagnostic xray

Back 40

too high energy needed: 1.02 MeV

Front 41

what happens during pair production..

Back 41

photon interacts with nuclear field, loses all its energy to the interaction and creates 2 e-

Front 42

what is photodisintegration

Back 42

occurs at extremely high energy: +10 MeV

Front 43

what happens during photodisintegration

Back 43

photon interacts with nucleus and all its energy is absorbed

Front 44

as kVp increases, the total number of photons transmitted _________ interaction increases

Back 44

without

Front 45

the probability of an interaction (PE/comptons) ______(increases or decreases) with the increase of kVp

Back 45

decreases

Front 46

As kVp increases:

the percentage of PE interactions ________ (increases or decrease)

the percentage of compton _____________ (increase or decrease)

Back 46

PE - decrease

compton - increase

Front 47

Define attenuation

Back 47

reduction in number and loss of energy of xray photons.