Radiology Radiation Physics

Front 1

What are the 4 states of matter?

Back 1

Duh
1. Solid
2. Liquid
3. Gas
4. Plasma

Front 2

T/F
Matter occupies space.

Back 2

True

Front 3

T/F
Each shell of the Bohr model of an atom has random energy level.

Back 3

False
Each shell has a Specific energy level

Front 4

What occurs when an atom loses an electron?

Back 4

Ionization

Front 5

What happens to the atom when it is ionized?

Back 5

1. Loses Electron
2. Nucleus becomes + ion
3. Electron becomes - ion
4. Formation of ion pair

Front 6

Ionizing an atom requires sufficient energy to overcome the ___________ binding the electrons to the nucleus.

Back 6

electrostatic force

Front 7

T/F
Within a given atom, electrons in the outer shells are more tightly bound than the more distant outer shells

Back 7

False
The inner shells are more tightly bound than outer shells

Front 8

What effect on the binding energy does having a Large Atomic Number (high Z), which has more protons in its nucleus?

Back 8

They bind electrons in any given shell more tightly than do smaller-Z elements

Front 9

T/F
Non-ionizing radiation, such as visible light, infrared, microwave radiation, and radio waves have sufficient energy to remove bound electrons from their shells.

Back 9

False
They DO NOT have sufficient energy to remove bound electrons from their shells

Front 10

What term refers to the particles which are emitted from nuclei as a result of nuclear instability?

Back 10

Radioactivity

Front 11

Name 3 different types of radiation.

Back 11

1. alpha (helium nucleu) two protons + two neutrons
2. beta (electron)
3. gamma (electromagnetic radiation)

Front 12

What type of radiation comes from a Helium nucleus (two protons & two neutrons)?

Back 12

Alpha radiation

Front 13

What type of radiation comes from electrons?

Back 13

Beta radiation

Front 14

What type of radiation comes from electromagnetic radiation?

Back 14

Gamma radiation

Front 15

What are examples of electromagnetic radiation?

Back 15

gamma rays, xrays, visible light, infrared radiation (heat), microwaves, and radio waves

Front 16

When using an xray machine, what percentage of incident energy is converted to heat and xray?

Back 16

99% heat
1% xray

Front 17

What are the 3 main components of an xray machine?

Back 17

Tube head
Arm
Control panel

Front 18

What part of the Tube Head is A?

Back 18

Power Sypply

Front 19

What part of the Tube Head is B?

Back 19

Aluminim Filter

Front 20

What part of the Tube Head is C?

Back 20

Aiming Cylinder

Front 21

What part of the Tube Head is D?

Back 21

Collimator

Front 22

What part of the Tube Head is E?

Back 22

Oil

Front 23

What part of the Tube Head is F?

Back 23

Yoke

Front 24

What part of the Tube Head is G?

Back 24

X-ray Tube

Front 25

What part of the Tube Head is G?

Back 25

X-ray Tube

Front 26

What part of an xray tube is A?

Back 26

Filament and Electron Cloud

Front 27

What part of an xray tube is B?

Back 27

Focal spot on tungsten target

Front 28

What part of an xray tube is C?

Back 28

Glass Envelope

Front 29

What part of an xray tube is D?

Back 29

Vacuum

Front 30

What part of an xray tube is E?

Back 30

Copper stem

Front 31

What part of an xray tube is F?

Back 31

Anode (+)

Front 32

What part of an xray tube is G?

Back 32

Useful xray beam

Front 33

What part of an xray tube is H?

Back 33

Tube Window

Front 34

What part of an xray tube is I?

Back 34

Cathode (-)

Front 35

What part of an xray tube is J?

Back 35

Electronic Focusing Cup

Front 36

What components of the X-ray Tube compose the Cathode?

Back 36

Cathode = Filament + Focusing Cup

Front 37

What components of the X-ray Tube compose the Anode?

Back 37

Tungsten Target Embedded in Copper Stem

Front 38

What are the major components of the X-ray tube?

Back 38

Cathode (filament +focusing cup)
Anode (tungsten target embedded in copper stem)
Casing (housing)
Power supply

Front 39

What is the formula for Photon Energy?

Back 39

E=hc/λ

Front 40

In the formula E=hc/λ, what does E equal?

Back 40

E= Photon energy

Front 41

In the formula E=hc/λ, what does h equal?

Back 41

h = Planck's constant

Front 42

In the formula E=hc/λ, what does c equal?

Back 42

c = speed of light

Front 43

In the formula E=hc/λ, what does λ equal?

Back 43

λ = wavelength

Front 44

What is the Focal Spot?

Back 44

The focal spot is the area on the target to which the focusing cup directs the electrons and from which xrays are produced.

Front 45

What happens to the sharpness of a radiographic image as the size of the focal spot decreases?

Back 45

Sharpnes increases as size of focal spot decreases

Front 46

Where are rotating Anodes used?

Back 46

Used in medical CT

Front 47

How are electrons generated in an xray tube?

Back 47

Heat the cathode filament to generate electrons

Front 48

How are the electrons generated by the heated cathode filament accelerated toward the anode?

Back 48

A high-voltage potential between the anode and cathode is established to accelerate the electrons toward the anode.

Front 49

What is the tube current?

Back 49

Tube current is the flow of electrons through the tube

Front 50

T/F
The mA setting on the filament current control refers to the current in the filament circuit.

Back 50

False
The mA setting on the filament current control actually refers to the tube current, typically about 10 mA. This is not the same as the current in the filament circuit.

Front 51

What amount of voltage is applied to the high voltage?

Back 51

60,000 - 100,000 Volts (or 60-100kV)

Front 52

What does the timer do in the xray tube circuitry?

Back 52

A timer is built into the high voltage circuit to control the duration of the xray exposure.

Front 53

What is the passage of an electron near a nucleus, which results in electrons being deflected and decelerated generating continuous spectrum of energy?

Back 53

Bremsstrahlung radiation (breaking or decelerated radiation)

Front 54

What are the properties of Characteristic Radiation?

Back 54

1. Incident electron ejects an inner electron from the tungsten target and an electron from an outer orbital is quickly attracted to the void in the deficient inner.
2. Subsequently, a photon is emitted with an energy equivalent to the difference in the two orbital binding energies.

Front 55

What property of Characteristic photons is because they represent the difference of the energy levels of electron orbital levels and hence are characteristic of the target atoms?

Back 55

The energies of characteristic photons are discrete

Front 56

What property of Characteristic photons is because they represent the difference of the energy levels of electron orbital levels and hence are characteristic of the target atoms?

Back 56

The energies of characteristic photons are discrete

Front 57

What is the difference in keV between Bremsstrahlung radiation and Characteristic radiation?

Back 57

Characteristic radiation is higher

Front 58

What are the 5 factors that control the x-ray beam?

Back 58

1. Timer (beam exposure duration)
2. Exposure rate (mA)
3. Energy (kVp & filtration)
4. Shape (collimation)
5. Intensity (target-patient distance)

Front 59

What controls the number of photons generated in a radiograph?

Back 59

Exposure time controls the duration of the exposure and thus the number of photons generated

Front 60

What happens the the photons generated when the exposure time is doubled?

Back 60

The number of photons generated at all energies in the x-ray emission spectrum is doubled.

Front 61

What is the quantity of radiation produced by an x-ray tube directly proportional to?

Back 61

Tube Current mA
Time the tube is operated

Front 62

What will increase the potential difference between the cathode and the anode, thus increasing the energy of each electron when it strikes the target?

Back 62

Increasing the Tube Voltage kVp

Front 63

What 3 things will increase when Tube Voltage in increased?

Back 63

1. Number of photons generated
2. Mean Energy
3. Maximal Energy

Front 64

T/F
The higher the kVp and mean energy of the x-ray beam, the greater the penetrability of the beam through matter.

Back 64

True

Front 65

What photons should be removed from the beam to reduce patient dose?

Back 65

Low-energy photons

Front 66

What preferentially removes many of the lower-energy photons with lesser effect on the higher-energy photons that are able to contribute to making an image?

Back 66

Aluminum Filter

Front 67

What is a metallic barrier with an aperture in the middle used to reduce the size of the x-ray beam and thereby the volume of irradiated

Back 67

A collimator

Front 68

What collimators are most frequently used in dentistry?

Back 68

Round and Rectangular Collimators

Front 69

T/F
Use of collimation improves image quality

Back 69

T

Front 70

In collimation the x-ray beam is directed at the patient, the hard and soft tissues absorb about ___ of the photons and about ___ pass through the patient and reach the film

Back 70

90%
10%

Front 71

What is the formula for the Inverse Square Law?

Back 71

For a given beam the intensity is inversely proportional to the square of the distance from the source

Front 72

What are 3 different interactions of X-rays with matter?

Back 72

1. Coherent Scattering
2. Photoelectric
3. Compton Scattering

Front 73

What is Coherent Scattering?

Back 73

1. Low-energy incident photon (<10 keV) passes near an outer electron
2. Photon causes electron to become momentarily excited at the same frequency
3. Photon ceases to exist
4. Excited electron returns to ground state & generates another x-ray photon w/the same energy as the incident beam
5. Secondary photon is emitted at an angle to the path of the incident photon

Front 74

Does Coherent scattering contribute to film fog?

Back 74

Coherent scattering contributes little to film fog because the number of scattered photons is small and their energy is too low for many of them to reach the film or sensor

Front 75

What percentage of the total number of interactions does coherent scattering account for in a dental exposure?

Back 75

Coherent Scattering accounts for 7% of the total number of interactions in a dental exposure

Front 76

What occurs when an incident photon gives up all of its energy to an inner electron ejected from the atom and an electron from a higher energy level fills the vacancy and emits a characteristic radiation?

Back 76

Photoelectric (radiation)

Front 77

How does Photoelectric radiation manifest on dental radiographs?

Back 77

Photoelectric radiation appears as a difference in optical density of the image.

Front 78

What occurs when an incident photon interacts with an outer electron, producing a scattered photon of lower energy than the incident photon and a recoil electron ejected from the target atom?

Back 78

Compton Absorption

Front 79

What percentage of x-ray interactions are compton?

Back 79

49%

Front 80

What effect does compton scattering have on an image?

Back 80

Scattered photons darken and degrade the image while carrying no useful information. Ionization occurs

Front 81

What does the absorption of the beam depend upon primarily?

Back 81

The Thickness & Density of the Absorber and the energy of the beam

Front 82

What is a measure of beam energy describing the amount of an absorber that reduces the beam intensity by half?

Back 82

HVL (Half Value Layer)

Front 83

What are the 2 systems for Disimetry?

Back 83

Traditional and International Systems

Front 84

In Dosimetry, what is the international system for measurements of Radiation?

Back 84

SI

Front 85

What is a measure of radiation quantity, the capacity of radiation to ionize air?

Back 85

Exposure

Front 86

What is the SI unit of exposure?

Back 86

kerma (kinetic energy released in matter)

Front 87

What does Kerma measure?

Back 87

Kerma measures the kinetic energy transferred from photons to electrons and is expressed in units of dose (gray [Gy], where 1 Gy = 1joule/kg

Front 88

What is a measure of the energy absorbed by any type of ionizing radiation per unit of mass of any type of matter?

Back 88

Absorbed dose

Front 89

What is the SI and Traditional units of measurement of Absorbed Dose?

Back 89

Absorbed Dose
SI = Gy (Gy = 1joule/kg)
Traditional = rad (radiation absorbed dose)
note: 1 rad is equivalent to 100 ergs/g of absorber. One gray = 100 rads

Front 90

What is used to compare the biologic effects of different types of radiation on a tissue or organ?

Back 90

HT (Equivalent Dose)

Front 91

What is the equivalent dose formula?

Back 91

HT =WR x DT

Front 92

What does WR represent in the Equivalent Dose Formula?

Back 92

WR represents the relative biologic effectiveness of different types of radiation

Front 93

What does DT represent?

Back 93

DT is the absorbed dose

Front 94

What is the WR of alpha particles and xrays?

Back 94

WR alpha particles = 20
WR x-rays = 1

Front 95

What is the unit of equivalent dose?

Back 95

HT is a sievert (Sv)

Front 96

What is used to estimate the risk in humans by allowing the risk from exposure to one region of the body to be compared with the risk from exposure to another region?

Back 96

Effective Dose

Front 97

What does E represent?

Back 97

E = effective dose

Front 98

What does WT represent?

Back 98

WT = tissue weighting

Front 99

What is the unit of effective dose?

Back 99

Sv

Front 100

In radioactivity, what describes the decay rate of a sample of radioactive material?

Back 100

Measurement of Radioactivity (A)

Front 101

What is the SI unit for Radioactivity?

Back 101

becquerel (Bq); 1 Bq = 1 dissintegration/second

Front 102

What is the traditional unit of radioactivity?

Back 102

Curie (Ci), which corresponds to the activity of 1 g of radium (3.7 x 1010 disintegrations/second)