Radiation Therapy Board Review

Front 1

Ionization

Back 1

neutral atom acquires a positive or negative charge

Front 2

Direct Ionization

Back 2

charged particles ie. electron, proton, alpha particle that have enough kinetic energy to produce ionization through collision as they penetrate matter

Front 3

Indirect Ionization

Back 3

uncharged particles... neutrons and photons... that liberate directly ionizing particles from matter when they interact with matter

Front 4

The two basic sources of ionizing radiation

Back 4

1. Natural or Background
2. Man-made radiation or X-rays

Front 5

Sources of background radiation

Back 5

1. Cosmic radiation
2. Terrestrial
3. Internal

Front 6

Examples of electromagnetic radiation

Back 6

radio waves
microwaves
visible light
x-rays
ultrasound

Front 7

X-rays

Back 7

electromagnetic radiation traveling at the speed of light in energy bundles moving through space as waves depositing energy randomly

Front 8

3 things need to create x-rays

Back 8

1. a source of electrons
2. a force to move them rapidly
3. something to stop them very rapidly

Front 9

Wavelength

Back 9

the physical distance between peaks of the wave in meters

Front 10

Amplitude

Back 10

one half the range from the crest to the valley over which the sine wave varies

Front 11

Frequency

Back 11

the number of wavelengths that pass a point of observation per second

Front 12

Velocity

Back 12

speed of a photon as it travels through space

Front 13

3 x 10^8 m/s

Back 13

The speed of all electromagnetic radiation

Front 14

Attenuation

Back 14

the reduction in x-ray intensity that results from absorption and scattering

Front 15

Inverse Square Law

Back 15

decrease in intensity is inversely proportional to the square of the distance of the object from the source

Double the distance quarter the dose

I1/I2 = (d2/d1)^2

Front 16

X-ray quality

Back 16

the penetrating ability of the radiation

Front 17

Half Value Layer (HVL)

Back 17

the thickness of an absorber of specified composition required to attenuate the intensity of the beam to half its original value

Front 18

T/F All X-ray beams produced by radiation generators are heterogenous in energy

Back 18

True

Front 19

Quality is described by peak energy at which energy level?

Back 19

Megavoltage

Front 20

HVL=

Back 20

0.693/u

Front 21

Photon interactions

Back 21

Photoelectric effect
Compton scattering
Pair Production
Photodisintegration
Coherent scattering

Front 22

Photoelectric effect energy range

Back 22

< or = 1 MeV like in diagnostic x-ray

Front 23

Photoelectric effect

Back 23

incoming photon interacts with an inner shell electron and transfers ALL its energy to that electron.

If energy absorbed is greater than the binding energy of the electron it is ejected.

Energy of ejected electron is = to the energy of the incoming photon - the binding energy

The inner shell electron is replaced by an outer shell electron and a Characteristic X-ray is produced.

Front 24

Auger Electron

Back 24

a electron that is ejected by a characteristic X-ray in the photoelectric effect.

Front 25

The most common interaction that occurs in radiation therapy?

Back 25

Compton scattering

Front 26

Compton scattering

Back 26

Incoming photon interacts with an outer shell electron whose binding energy is much less than the energy of the incoming electron.

The electron is ejected and the photon is scattered at an angle

Front 27

The 3 Types of interactions with Compton

Back 27

Direct hit- Electron forward...photon backward
Grazing hit- Photon forward... electron emitted at a 90 degree angle
90 degree scatter- Photon scatters at 90 degrees from original direction

Front 28

Pair Production

Back 28

High energy photons interacting with the electromagnetic field of the nucleus.

Energy is absorbed and an is ejected as an electron and positron

Front 29

Pair Production energy level

Back 29

> 1.022 MeV

Front 30

Annihilation radiation

Back 30

In pair production the positron produced can recombine with an electron and create 2 photons that are ejected in opposite directions with an energy of .511 MeV respectably.

Front 31

Photodisintegration energy

Back 31

> 10 MeV and have a high Z material

Front 32

Photodisintegration

Back 32

Incoming photon is absorbed by the nucleus and a neutron is emitted as a gamma ray

Front 33

Thomas scattering

Back 33

Also known as coherent scattering

Front 34

Coherent scattering

Back 34

A low energy incident photon is absorbed by an electron and emitted in a new direction with the exact same energy

Front 35

How do electrons interact with matter?

Back 35

Through inelastic and elastic collisions

Front 36

Elastic collisions

Back 36

redistribute energy among particles emerging from the collision

High energy electrons decrease in energy at a rate of 2 MeV.cm in soft tissue

Front 37

Inelastic collisions

Back 37

Kinetic energy is lost in production of ionization or is converted to other forms of energy

Front 38

Heavy charged particles

Back 38

Have an electric charge and an amu of at least 1

Front 39

Heavy charged particle interaction

Back 39

interact with atoms through coulomb forces between the electrical field of the particle and the atom

Front 40

Stopping power (S)

Back 40

The rate of kinetic energy loss per unit path length of the particle

Front 41

Bragg peak

Back 41

The peaking dose near the end of the particle range

Front 42

Electron Interactions

Back 42

Very similar to heavy particle interactions but because of small mass the electrons suffer greater multiple scattering and change of direction and as a result there is no Bragg peak

Front 43

Neutron interactions

Back 43

Interact by ejecting recoil protons or producing nuclear disintegration

Front 44

Law of Bergonie & Tribonideau

Back 44

Cells are most sensitive to radiation when they are actively proliferating and undifferentiated

Front 45

LET

Back 45

Linear Energy Transfer

The rate at which energy is deposited as a charged particle travels through matter

Front 46

RBE

Back 46

Relative Biological Effectiveness

RBE = Dose of standard radiation necessary to produce a given effect / dose of test radiation necessary to produce the same effect

Front 47

LET and RBE

Back 47

As LET increases so does the RBE

Front 48

OER

Back 48

Oxygen Enhancement Ratio

THe ratio of dose required for equivalent cell killing in the absence as compared to the presence of oxygen

Oxygen is a radiosensitzer

Front 49

Deterministic radiation response

Back 49

Threshold dose where the severity increases with increasing dose

example: radiation skin burns

Front 50

Stochastic radiation response

Back 50

Severity independent of dose but probability increases with dose so NO threshold dose

example: cancer

Front 51

Somatic effects

Back 51

Are late effects of radiation exposure to cells but are not transferred to future generation

example carcinogenesis

Front 52

Genetic effects

Back 52

appear in the future generations of the exposed person as a result of radiation damage to the reproductive cells.

Front 53

Radiation and the cell cycle

Back 53

M phase is most sensitive to radiation
S phase is most resistant to radiation

Front 54

The 4 R's of radiobiology

Back 54

Repair
Re-oxygenation
Reassortment/Redistribution
Repopulation

Front 55

Hemopoietic System

Back 55

Blood, marrow and lymph

Front 56

Radiation and bone barrow

Back 56

Decreases the number of stem cells in marrow

Erythroblasts are the most radiation sensitive cells in marrow

Megakaryocytes are the most radiation resistant cells in marrow

Front 57

Radiation and blood

Back 57

Lymphocytes are the most radiosensitive
Decreased WBC increased infection risk
Decreased RBC = anemia
Decreased platelets increased hemorrhage risk

Front 58

Early responding tissues

Back 58

Days- weeks
Epithelial cells e.g. skin reddening
uncomfortable but rarely lethal and usually recoverable
Tumors behave as an early reacting tissue

Front 59

Late responding tissues

Back 59

months to years - fibrosis and organ failure
e.g. lung, spine, heart, kidney failure

Front 60

Acute skin reactions

Back 60

inflammation
erythema (2000 cGy)
dry desquamation (2000 cGy - 4000 cGy)
moist desquamation (> 4000 cGy)

Front 61

Chronic skin reactions

Back 61

Atrophy
fibrosis
Hyper/hypo pigmentation
necrosis

Front 62

Male permanent sterility

Back 62

5-6 Gy

Front 63

Male temporary sterility

Back 63

2.5 Gy

Front 64

Male reproduction and radiation

Back 64

immature spermatagonia are very radiosensitive

possible genetic damage that could affect future generations

Front 65

Female sterility

Back 65

6.25 Gy

Front 66

Female reproduction and radiation

Back 66

possible genetic damage that could affect future generations

Ovaries very radiosensitive

Front 67

The GI system and radiation

Back 67

small bowel = most radiosensitive
Rectum and esophagus most radio resistant

Front 68

Most radio-resistant system in the body?

Back 68

CNS

Front 69

White and gray matter and radiation

Back 69

Gray matter is more radio-resistant than white matter

Front 70

TBI acute effects

Back 70

Hematopoietic syndrome
Gastrointestinal syndrome
Cerebrovascular syndrome

Front 71

Hematopoietic syndrom

Back 71

2.5-5 Gy
Death in within a matter of weeks to months from a lack of immune system

Front 72

Gastrointestinal syndrome

Back 72

5-12 Gy
Death within a matter of days due to destruction o gastrointestinal mucosa leading to intestinal failure

Front 73

Cerebrovascular syndrome

Back 73

100 Gy
death in a matter of a day or two due to neurologic and cardiovascular breakdown

Front 74

Fetus and radiation

Back 74

0-9 days = spontaneous abortion
10 days - 6 weeks (organogenesis) = congenital anomalies and growth retardation
6-40 weeks = growth and cognitive problems

Front 75

Carcinogenesis

Back 75

The process by which normal cells are transformed into cancer cells

Front 76

USA unit of exposure

Back 76

Roentgen (R)

Front 77

USA unit of absorbed dose

Back 77

Rad (radiation absorbed dose)

Front 78

USA biological equivalent dose

Back 78

Rem (radiation equivalent man)

Front 79

USA Unit of activity

Back 79

Curie (Ci)

Front 80

SI unit of absorbed dose

Back 80

Gray (Gy)

Front 81

SI unit of biological equivalent dose

Back 81

Sievert (Sv)

Front 82

SI unit of activity

Back 82

Becquerel (Bq)

Front 83

Absorbed dose (Gy)

Back 83

one Gy = one joule of energy deposited in on kg of a material

1 Gy = 100 rads

Front 84

Exposure measurement (R)

Back 84

Describes an amount of gamma and X-rays only in air
No equivalent unit in SI system
Not used very often

Front 85

Equivalent dose (rem)

Back 85

Relates absorbed dose in human tissue to effective biological damage

Not all radiation types have same biological effect

1 Sv = 100 rem

Front 86

Kerma (kinetic energy released per unit mass... of air)

Back 86

Measure of amount of radiation energy in joules (J) actually deposited in or absorbed in a unit mass (kg) of air

expressed as J/kg which is the same as the gray (Gy)

Front 87

Personnel monitoring devices

Back 87

Film badge dosimeter
TLD
OSL
pocket ionization chamber

Front 88

TLD (Thermoluminescent Dosimeter)

Back 88

Traps electrons in their crystal when exposed to radiation

light is given off when heated -> amount of light determines radiation exposure

more expensive than film badges

less sensitive to heat and humidity

sent out to be read

Front 89

OSL (optically stimulated luminescence) dosimeter

Back 89

electrons trapped in the aluminum oxide when it is exposed to radiation

more sensitive than film

can estimate dose at depths

accurate within 1 mrem

Front 90

Geiger-Muller Counter

Back 90

very sensitive and strongly energy dependent

can detect very small amounts of radiation

Front 91

Ionization chamber

Back 91

composed of 2 electrodes, electronics and a meter that amplifies and measures the electrical signal

Should be run at a high voltage so the all the ion pair are collected and no recombine

The sensitivity depends on the mass of gas in the chamber

accurate within 2 %

used to measure output of therapy equipment

Front 92

Diodes

Back 92

composed of an anode and a cathode

used for relative dosimetry... output consistency checks and in vivo patient dose monitoring

Front 93

Neutron detector

Back 93

used to detect neutron radiation

example: Scintillation neutron detector

Front 94

ALARA

Back 94

As Low As Reasonably Achievable

Front 95

Basic methods of protection for radiation exposure

Back 95

Time
Distance
Shielding

Front 96

CFR 10, parts 20 and 35

Back 96

Facility and regulation guidelines

Front 97

Shielding parameters

Back 97

Use factor (U)
Workload (W)
Occupancy factor (T)
Effective dose (P)

Front 98

Use Factor (U)

Back 98

the number of time in a day the radiation beam is directed toward a particular barrier

Front 99

Workload (W)

Back 99

the amount of patients per week multiplied by the amount of radiation for each person

Front 100

Occupancy factor (T)

Back 100

refers to the amount of time the rooms next to the treatment room are occupied

Front 101

Effective dose (P)

Back 101

The radiation limit for the occupied area

Front 102

Use factors for primary barriers

Back 102

Floor = 1
Walls = 1/4
Ceiling = 1/4-1/2

Front 103

Primary barriers

Back 103

protect against DIRECT exposure from the primary beam

Front 104

Secondary barriers

Back 104

Protect against leakage and scatter radiation

Front 105

Occupational Exposure (stochastic)

Back 105

Annual: 50 mSv or 5 rem
Cumulative: 10mSv x age / 1rem x age

Front 106

Occupational exposure (non-stochastic)

Back 106

Lens of eye: 150 mSv or 15 rem
Skin, hands, feet: 500 mSv or 50 rem

Front 107

Annual public exposure

Back 107

Effective dose for infrequent exposure: 1mSv or 100mrem

Effective dose for tissues: 5mSv or 500mrem

Lens of eye: 15mSv or 50 mrem

Skin and extremities: 50mSv or 5 rem

Front 108

18 or younger exposure

Back 108

annual effect dose limit: 1mSv or 100mrem

Front 109

Emryo/Fetus

Back 109

total effective dose: 5mSv or 500mrem

Monthly effective dose: .05mSv or 50mrem

Front 110

Uncontrolled/unrestricted area

Back 110

0.02 mSv/ week or 1mSv/year

areas occupied by the general public

Front 111

Controlled/restricted area

Back 111

1 mSV or 100mrem/wk

barriers and engineering controls in place to reduce exposure

Front 112

Caution radiation area sign

Back 112

exposure of more than 5mrem/ hr or 100 mrem in 5 days

Front 113

Caution High radiation sign

Back 113

greater than 100 mrem/hr

Front 114

Radiation symbol colors

Back 114

three-bladed symbol in magenta and a yellow background

Front 115

Caution Radioactive material

Back 115

when the quantity of the nucleotide exceeds the activity specified by local law

eg HDR room

Front 116

MSDS

Back 116

Material Safety Data Sheets

intended to provide workers and emergency personnel with procedures for handling or working with that substance in a safe manner, and includes information such as physical data (melting point, boiling point, flash point, etc.), toxicity, health effects, first aid, reactivity, storage, disposal, protective equipment, and spill-handling procedures

Front 117

Shielding blocks

Back 117

Composed of cerrobend

BLT w/ Cheese

50% Bismuth
26.7% Lead
13.3% Tin
10% Cadmium - Toxic!

Front 118

Radium 226

Back 118

1622 yrs half life

.830 MeV

Front 119

Cobalt 60

Back 119

5.27 yrs half life

1.25 MeV

Front 120

Cesium 137

Back 120

30.0 yrs half life

.662 MeV

Front 121

Iridium 192

Back 121

73.83 days half life

.380 MeV

Front 122

Iodine 125

Back 122

59.4 days half life

.028 MeV

Front 123

Palladium 103

Back 123

16.99 days half life

.021 MeV

Front 124

Gold 198

Back 124

2.7 days half life

.412 MeV

Front 125

Radon 222

Back 125

3.82 days

.78 MeV

Front 126

Back 126

Front 127

Back 127

Front 128

Back 128

Front 129

Back 129

Front 130

Photons

Back 130

Front 131

Electrons

Back 131

Front 132

5 main components of accelerator?

Back 132

Drive stand
patient support assembly (PSA)
Electronic cabinet
Console

Front 133

Two types of bending magnets used?

Back 133

90 or 270 degree bending magnet

Front 134

___________ ______ _______________ keep track of dose rate and field symmetry

Back 134

Monitoring ion chambers

Front 135

_______________ _________________ are used to localize the target volume using fluoroscopy and/or static two-D radiographic imaging

Back 135

Conventional simulators

Front 136

Name to advantages to CT simulators compared to conventional simulators?

Back 136

visualize 3-D data

easily see different tissue densities

Front 137

How often do the interlocks on the linear accelerator need to be checked?

Back 137

Daily

Front 138

T/F? A beam on indicator light is mandatory?

Back 138

True

Front 139

T/F? The emergency off switch is required to be tested daily?

Back 139

False

Front 140

Localizing lasers on simulators must be within_______________ of isocenter.

Back 140

2mm

Front 141

Full calibration and overhaul of treatment equipment must be carried out how often?

Back 141

Annually

Front 142

The components of a linear accelerator revolve around isocenter on their respective axes. What is the tolerance for locating the isocenter in these rotation is a sphere of?

Back 142

2mm in diameter

Front 143

How often do the electron and photon beams need to be checked on a linear accelerator?

Back 143

Daily

Front 144

What is the tolerance for the localizing laser on the ODI?

Back 144

2mm

Front 145

How does the linear accelerator generate a high energy photon or electron?

Back 145

By accelerating charged particles in a linear path

Front 146

T/F? as the distance from the source increases the penumbra decreases

Back 146

False

Front 147

What is the target in the linear accelerator made of?

Back 147

Tungsten

Front 148

What is the tolerance for the scan and couch vertical positioning accuracy for CT planning?

Back 148

2mm

Front 149

Door interlocks must be checked __________

Back 149

Daily

Front 150

Gantry and collimator angles must be accurate within how many degrees?

Back 150

1 degree