Concepts of Dose Calculations Pt. 1

Question 1

Ionizing Radiation

Answer 1

Electromagnetic/particular radiation capable of producing ion pairs by interacting with matter

Question 2

What are 6 examples of ionizing radiation?

Answer 2

X-rays, Gamma Rays, Alpha, Beta, Neutrons and Charged nuclei

Question 3

What are the three IR interactions in radiotherapy?

Answer 3

Photoelectric, Compton and Pair Production

Question 4

What is the unit of activity?

Answer 4

Ci and Bq

Question 5

What is the unit of ionization in air?

Answer 5

R

Question 6

What does KERMA stand for?

Answer 6

Kinetic Energy released in medium

Question 7

What is the unit for absorbed dose?

Answer 7

Rad/Gy

Question 8

What is the unit for dose equivalent?

Answer 8

Rem/Sv

Question 9

1 Curie = ? Bq

Answer 9

3.7e10 dps

Question 10

What is exposure? Unit?

Answer 10

the measure of ionization in the air. Roentgen

Question 11

What is the equation for exposure?

Answer 11

exposure (X)= Charge(Q)/Mass (M)

Question 12

What are 3 things exposure is defined by?

Answer 12

For photons, ionization of dry air, ionization at elect equilibrium

Question 13

what is the SI for exposure?

Answer 13

2.58e-4 C/Kg

Question 14

What is charge particle equilibrium

Answer 14

If a leaving charged particle is leaving, and replaced by another charged particle of the same type and same energy, then there is charged particle equilibrium (If a negative 21 keV electron leaves and another 21 keV neg electron comes in then its “normal”

Question 15

What is the equation for KERMA?

Answer 15

KERMA= Kcol+Krad

Question 16

What is Kcol?

Answer 16

part of energy lost due to collision with atoms, resulting in excitation or ionization

Question 17

What is Krad?

Answer 17

energy lost in producing Bremsstrahlung photons

Question 18

What is the greater component of KERMA?

Answer 18

Kcol

Question 19

What is the equation of dose components?

Answer 19

Primary Beam + Sum of all scatterings

Question 20

What is radiation absorbed dose?

Answer 20

Amount of radiation absorbed within a material

Question 21

What are the units of Radiation absorbed dose?

Answer 21

1 Rad= 100 ergs/gram

Question 22

1 Gy = ?,?

Answer 22

100 cGy/Rad, 1 J/kg

Question 23

1 cGy =?

Answer 23

1 Rad

Question 24

The equation for absorbed dose?

Answer 24

Dose= Energy absorbed (directly or indirectly)/ mass of material

Question 25

f factor?

Answer 25

Conversion factor from Roentgen to cGy

Question 26

What are the two factors that affect the f Factor?

Answer 26

Density of the matter and the Beam energy

Question 27

Absorbed = ____ x Exposure?

Answer 27

f Factor

Question 28

What is the f Factor for dose in the air?

Answer 28

0.876

Question 29

What is the f Factor for dose in a medium?

Answer 29

0.956

Question 30

fmed= ?/?

Answer 30

Mass attenuation coeff in medium/mass attenuation coeff in air

Question 31

Dose equivalent equation?

Answer 31

H= Absorbed dose x quality factor

Question 32

What is the significance of H in the dose equivalent equation?

Answer 32

Takes into account the radiobiological effectiveness and depends on the dose and type of radiation

Question 33

What is the quality factor?

Answer 33

factor that compares biological effectiveness of a particulate form of radiation to a standard x-ray radiation

Question 34

H(?)=D(rad)x Quality factor

Answer 34

Rem and Rad

Question 35

What is the quality factor for photons, gamma ray, electrons?

Answer 35

1

Question 36

What is the quality factor for alpha particles?

Answer 36

20

Question 37

What is the quality factor for neutrons/protons?

Answer 37

10

Question 38

What is the 1st type of photon interaction?

Answer 38

The photon can penetrate through the matter without interacting

Question 39

What is the 2nd type of photon interaction?

Answer 39

The photon can be completely absorbed into matter and deposit its energy

Question 40

What is the 3rd type of photon interaction?

Answer 40

The photon can be scatters or deflect from original path and deposit some of its energy

Question 41

What is the electron build up region?

Answer 41

The region in which small deposits of the dose are made and built up until the point of maximum deposition of dose, known as Dmax

Question 42

What is Dmax?

Answer 42

Depth of maximum ionization, max absorbed dose occurring for a single photon fields

Question 43

What affects Dmax?

Answer 43

Beam Energy

Question 44

As BE increases, what occurs to Dmax?

Answer 44

Depth of Dmax increases

Question 45

Where does Dmax occur for LE? HE?

Answer 45

LE is on the surface of the skin and HE is beneath the skin

Question 46

What is the Dmax for Co-60, 4, 6, 10, 15, 18MV?

Answer 46

1. 0.5 2. 1.2 3. 1.5 4. 2.5 5. 3.0 6. 3.3