Calibration of Dose Output/ Radiation measurements

Question 1

Exposure is a measurement in ____

Answer 1

air

Question 2

What are the stipulations for exposure?

Answer 2

Only under 3MeV
Only measured in air

Question 3

The quantity of radiation for all types of ionizing radiation, (charged and uncharged), all materials and all energies

Answer 3

Absorbed dose

Question 4

SI unit for absorbed dose

Answer 4

Gray

Question 5

Traditional unit for absorbed dose

Answer 5

Rads

Question 6

the biological effect of radiation depends on the dose and also type of radiation

Answer 6

Dose equivalent (H)

Question 7

Used to assess risk from radiation and not radiation prescriptions?

Answer 7

Dose equivalent (H)

Question 8

Traditional unit for (H)

Answer 8

rem

Question 9

SI unit for (H)

Answer 9

Sievert (SV)

Question 10

Quality Factor (Q)

Answer 10

accounts for how different radiation types affect cells differently

Question 11

Unit of Q

Answer 11

Unitless

Question 12

Q is similar to using___

Answer 12

RBE

Question 13

Quality factor for xrays, gamma rays and electrons

Answer 13

1

Question 14

Quality factor for neutrons, energy < 10keV

Answer 14

5

Question 15

Quality factor for protons

Answer 15

2 or 1.1

Question 16

Quality factor for alpha particles

Answer 16

20

Question 17

the ratio of the dose of 250 kVp xrays to produce a specified biological effect to the dose of the given radiation to produce the same effect

Answer 17

RBE

Question 18

when a volume is irradiated by photons, energy is given to charged particles by such photons

Answer 18

Collisional Kerma

Question 19

The energy given to irradiation volume is ______ to energy given to charged particles

Answer 19

equal

Question 20

???Kerma is _____ in the buildup region compared to absorbed dose

Answer 20

higher

Question 21

After dmax, what happens to absorbed dose compared to kerma

Answer 21

it is higher than kerma

Question 22

Deeper the buildup region

Answer 22

the greater the skin sparing

Question 23

Look up redmaxing effect

Question 24

F med (F factor) converts?

Answer 24

Roentgen to Rad (exposure to dose)

Question 25

What is the mean energy required to produce an ion pair in dry air (constant for all electron energies)

Answer 25

W= 33.97 eV/ionpair

Question 26

D=X * W/e

Answer 26

33.97 J/C * 2.58 x 10^-4 c/kgR = 0.876 rad/R

Question 27

Transmission factor in air

Answer 27

AQE

Question 28

Factor to take dose in air to dose in other media

Answer 28

Dair = 0.876 * X * A

Question 29

The energy loss by electrons per unit path length of a material

Answer 29

stopping power

Question 30

Two types of stopping power

Answer 30

Collisional and radiative

Question 31

Limitations in calculations from absorbed dose from exposure

Answer 31

derived from exposure in air only valid for photons <3MeV

Question 32

Ratio for the number of photons or particles passing through a cross sectional area of a sphere

Answer 32

Fluence

Question 33

Units of fluence

Answer 33

1/cm^2 or cm^-2

Question 34

the ratio of radiant energy passing through a sphere of cross-sectional area

Answer 34

fluence energy

Question 35

Photons in a fluence can be

Answer 35

monoenergetic or polyenergetic

Question 36

How to find energy fluence

Answer 36

Take the number of photons x the keV of each and add together i.e (photons/cm^2 * keV) + (photons/cm^2 * keV)

Question 37

KERMA

Answer 37

Kinetic energy released in Matter per unit mass

Question 38

energy transfer via radiative photons (bremsstrahlung (g))

Answer 38

Radiative KERMA

Question 39

collisions between photons and charged particles results in electrons which dissipate energy via collisions leading to ionization and excitation

Answer 39

Collisional KERMA

Question 40

KERMA units

Answer 40

Gy

Question 40

Kerma is defined

Answer 40

in any medium and indirectly ionizing radiation (Photons and neutrons)

Question 41

occurs when the number and energy of charged particles (electrons) are equal entering and exiting the measurement volume

Answer 41

Charged particle equilibrium (CPE)

Question 42

CPE is used to measure

Answer 42

Exposure (ion chambers)

Question 43

measure the charged produced in air volum by the electrons liberated by a photon beam

Answer 43

ion chamber (plus electrometer)

Question 44

Electonmeter has what type of voltage

Answer 44

bias

Question 45

pros of bias voltage

Answer 45

-keeps ions from recombining and not being read by ion chamber

Question 46

what is bias voltage

Answer 46

no ground and it isn't held at a neutral voltage

Question 47

what are free air ion chambers used for

Answer 47

primary devices that check clinical devices

Question 48

A free air ion chamber is

Answer 48

an open system to the outside air

Question 49

combined before can be read by collecting device/ charge created by never collected

Answer 49

Ion Recombination

Question 50

Desirable ion chamber characteristics

Answer 50

- minimal variation in sensitivity or exposure calibration factor over wide energy range - minimal dependence with direction of incident radiation -minimal stem leakage -minimal ion recombination -should be calibrated against a primary standare

Question 51

Cons of free-ion chambers

Answer 51

-air density changes, temp, pressure and humdity -Ion recombination -air attenuation of photons -secondary chamber chambers calibrated against free air chamber use expousre calibraion factors

Question 52

Thimble chamber has what surrounding it

Answer 52

solid air shell; material made with equivalent Z as air

Question 53

Wall on thimble chamber has to be as thick as what?

Answer 53

as thick as max electron range, may need buildup cap for higher energies

Question 54

What must a thimble chamber have to measure exposure

Answer 54

-Have a defined cavity volume -be air equivalent -wall thickness to provide electronic equilibrium

Question 55

Thimble chamber must be calibrated at

Answer 55

a national lab that uses a FAC

Question 56

Not really in practice now, example is victoreen R meter

Answer 56

Condenser chamber

Question 57

Farmer chamber measures

Answer 57

photon exposure in the therapeutic energy range

Question 58

Farmer chamber wall is

Answer 58

pure graphite (tissue equivalent)

Question 59

Central electrode of farmer chamber

Answer 59

Pure aluminum

Question 60

Farmer chamber insulator is

Answer 60

polytricholorfluoroethylene

Question 61

Collection volume of farmer chamber

Answer 61

0.6cm^3

Question 62

Farmer chamber has ____ electrodes

Answer 62

Three

Question 63

Bias voltage volts

Answer 63

300