Physics Final Fall 2009 Flashcards For New Material

Front 1

characteristic radiation occurs when...?

Back 1

e- interact with inner orbital e- instead of nucleus
incident e- knock out inner orbital e-
atom left in ionized state

Front 2

incident e- leaves with energy (equation)

Back 2

Ef=Eo-Et

Et=energy imparted to orbital e-

Front 3

orbital e- leavew ith energy (equation)

Back 3

Ee=Ef-Ek

Ek=binding energy

Front 4

ionized atom then has lower level e- which ________and creates a __________

Back 4

loses energy

creates a photon

Front 5

photon created from lower level e- moving up and losing energy is called

Back 5

characteristic radiation

Front 6

equation for characteristic radiation (photon equation)

Back 6

hv= Ek-El

Ek=binding energy of inner orbit

El=binding energy of outer orbit

Front 7

characteristic radiation is .....

Back 7

characteristic of where it takes place

L radiation = L shell knocked out
K radiation = K shell knocked out

Front 8

as energy increases, characteristic radiation

Back 8

decreases

Front 9

relationship between energy and characteristic radiation is

Back 9

indirectly proportional

Front 10

relationship between characteristic radiation and megavoltabe x-ray machines?

Back 10

none, characteristic radiation is not seen in megavoltage x-ray machines just bremsstralung

Front 11

3 methods photons and e- interact

Back 11

photoelectric interaction

compton interaction

pair production

Front 12

as energy increases teh % of initial energy retained in photoelectric interaction__________

Back 12

decreases at all angels except 0 degrees

Front 13

what provides diagnostic contrast

Back 13

photoelectric interaction

Front 14

what is a photoelectron

Back 14

an ejected e- from the inner shell knocked out by a photon

Front 15

characteristic radiation aka

Back 15

florescent radiation

Front 16

electromagnetic radiation that causes 2nd e- called ______ to be ejected

Back 16

auger e-

Front 17

energy given to photoelectric e- (equation)

Back 17

Ek= hv-Eb

Front 18

k shell binding energy

Back 18

.5 kev or 500 ev photon/electron=low

Front 19

characteristic radiation is emitted w/an energy of

Back 19

.5kev with little to no Bremstralung

Front 20

with increasing Z materials

Back 20

e- is held tighter
= increasing binding energy

Front 21

greatest angle e- can be scattered

Back 21

90 degrees

Front 22

characteristic radiation
adv
dis

Back 22

adv= mono energetic

dis= bremstrullungs are greater in # than characteristic radiation

Front 23

absorbtion edges are associated with

Back 23

photoelectric attenuation

Front 24

at photon increases

Back 24

photoelectric attenuation decreases

Front 25

photoelectric attenuation coefficient increases abruptly when

Back 25

energy of photon equals binding energy of shell

Front 26

when photon energy =binding energy

Back 26

produces discontinuities in attenuation curve= absorption edges

Front 27

discontinuities in attenuation curve

Back 27

absorption edges

Front 28

photoelectric effects predominate in

Back 28

H20 < 50kev (max 200kvp or 66kev)

Pb <500kev

Front 29

photoelectric attenuation varies as

Back 29

1/E3 of the photon

Z3 of the absorber- more probable in bone than tissue

Front 30

Our friend

Back 30

compton interaction

Front 31

ther are more ___interaction than______

Back 31

photoelectric interactions than compton interactiosn

Front 32

interaction of photon w/unbound e- (outer e- with low binding energy)

Back 32

compton effect

Front 33

unbound e-

Back 33

binding energy is low so considered free e-

Front 34

type of interacition in compton effect

Back 34

elastic

Front 35

______composed of low atomic #

Back 35

free electrons (soft tissue)

Front 36

in _____ photon ejects e- and e- receives part of energy, photon receds from collison with reduced energy

Back 36

compton effect

Front 37

equation for compton effect

Back 37

hv-hv1 + Ee

Front 38

photon direct hit with e-

what angle?

Back 38

e-travels straight forward
photon straight back
e= max energy
photon =minimum

degree angle= 180

Front 39

photon grazes e-

what angle

Back 39

photon straight forward
photon maintains all energy
e- receives non form photon

angle 90

Front 40

Compton wavelength

Back 40

change in wavelength of photon

Front 41

Compton
low energy photon

Back 41

e aquires little energy phon gets most energy

Front 42

Compton
high energy photon

Back 42

recoil e- gets most energy

Front 43

how does Z affect comtpton effect?

Back 43

it doesn't because Compton is independent of Z (atomic number)

Front 44

as energy ____ probablity of compton interaction______

Back 44

increases probability of compton decreases (indirectly related)

Front 45

in soft tissue the range 60kev-20mev, ________ is more important than _____or ____________

Back 45

compton is more important than pair production or photoelectic

Front 46

soft tissue ranges for compton

Back 46

60kev-20mev

Front 47

does pair production occur in diagnostic range?

Back 47

no! starts at 1.02 Mev

Front 48

what is pair production

Back 48

when a photon passes near the nucleus of atom and is subjected to the field of the nucleus. photon may disappear and become e- or e+

Front 49

pair production relationship to E=mc2

Back 49

energy of photon turned into mass (e- and e+

Front 50

probability of pair production ___as photon energy ____

Back 50

increases
increases
(directly related)

Front 51

pair production relationship with Z

Back 51

vaires as Z2

Front 52

What is triplet production

Back 52

same as pair production except interactons occurs with electron fields

Front 53

what results from triplet production

Back 53

e- e+ and initial e-

Front 54

threshold for triplet production

Back 54

2.04Mev

Front 55

probability of triplet production

Back 55

1-10% as often as pair production

Front 56

above 20Mev-

Back 56

pair production is the most important process by which energy is absorbed

Front 57

fem heads get great dose with?

Back 57

pair production and there is shadowing of the prostate

Front 58

T/F
Can a 10Mev electron have a compton interaction in tissue

Back 58

FALSE because its an e- and not a photon

Front 59

types of interactions with e- and photons

e- =
photon=

Back 59

e= collisions an bremstrulung

photon= photoelectic, compton, pair production

Front 60

bone absorbs 6 times as much energy gm for gm as tissue

Back 60

photoelectric

Front 61

bone and tissue absorb the same amount gm for gm

Back 61

compton

Front 62

bone absorbs 2times as much energy gm for gm

Back 62

pair production

Front 63

why we treat with photons

Back 63

skin sparing
goes deeper
carry energy deeper because they have no charge or mass when they interact they produce electrons= dose=biological changes

Front 64

T/F photons don't give does, they carry energy which is released by electrons (production of an interaction)

Back 64

true

Front 65

compton
as energy of photon____ scattering angle___ for photon and e-

Back 65

increases, decreases
(indirectly proportional)

Front 66

compton
as energy of photon___, more energy is given to e-

Back 66

increases

Front 67

if photon is scattered at 90 degrees

Back 67

max energy it can have is .511mev
e- scattered directly forward

Front 68

if photon is scattered at 180 degrees

Back 68

e- given max amount of energy and
photon gets minimum

Front 69

if photon is scattered at 0 degrees

Back 69

photon gets max amount
e is deftected at 90 degree angle
e gets no energy from incident photon

Front 70

form of Co60

Back 70

disk, cylinder, pellet, encapsulated in stainless steel capsule

Front 71

type of capsule

Back 71

dbl stainless steel to prevent leakage

Front 72

use waffers to

Back 72

fill inner capsule for varying amount of co60

Front 73

housing around capsule

Back 73

lead for shielding purposes

Front 74

source of "on" "off" mechanism

Back 74

1 rotation wheel
2. horizontally driven drawer
3. mercury switch

Front 75

how are mechanisms "fail safe"

Back 75

must have power for motor to keep open, when power goes off it closes

Front 76

2 sets of collimators for co60

Back 76

primary
secondary

Front 77

primary is

Back 77

stationary
close to the source
defined larges filed size possible

Front 78

secondary is

Back 78

variable collimators
fld size used to treat

multiplane, made of depleted uranium
inner surface always parallel to beam , diverge with source/beam

Front 79

how do you avoid e- contamination in co60

Back 79

have secondary collimators at least 15-20 cm away from patient

Front 80

source diameter for co60

Back 80

1-2cm in diameter

Front 81

increase diameter of source=

Back 81

stronger source
BUT
larger source diameter=large pneumbra

Front 82

pneumbra equation

Back 82

w=s ((SSD-SCD)/
SCD)

pneumbra= source diameter ((skin to source distance- source to collimator distance) / source to collimator distance)

Front 83

other isotopes used for teletherapy in teh past

Back 83

Ra Cs

Front 84

Co60 developed in

Back 84

1952

Front 85

standard source strength

Back 85

4000-10,000 RHM

Front 86

1RHM=

Back 86

1Ci

Front 87

# of photons=

Back 87

dose rate created

Front 88

probability of making x-rays is

Back 88

1%, the rest is heat

Front 89

probability of making x-rays for linear accelerator

Back 89

50%

Front 90

type of x-ray used in both diagnostic and radiation therapy

Back 90

bremsstrulung