Radiology Exam 1 Radiation Physics

Front 1

Radiation:

Back 1

Energy in transit

Front 2

Radioactivity:

Back 2

The characteristic of various materials to emit ionizing radiation

Front 3

The removal of electrons from an atom

Back 3

Ionization

Front 4

Alpha, beta and cathode rays

Back 4

Particulate Radiation

Front 5

transmit KE by means of small masses moving at high velocities

Back 5

Particulate radiation

Front 6

Gamma rays, x-rays, visible light

Back 6

EMR

Front 7

Movement of energy through space as a combination of electric and magnetic fields

Back 7

EMR

Front 8

Rate of loss of energy of a particle as it moves along its path in an absorber:

Back 8

Linear Energy Transfer (LET)

Front 9

Directly related to the mass

Back 9

LET

Linear Energy Transfer

Front 10

KE =

Back 10

½ mV^2.

Front 11

Electric and magnetic fields are in planes at right angle T or F?

Back 11

T

Front 12

What is frequency?

Back 12

amount of oscillations or cycles per second

Front 13

wavelength and the frequency are inversely related T or F?

Back 13

T

However the velocities of all EMR is the same

Front 14

What is a wavelength

Back 14

The wavelength is the distance between crest and trough (successive). If the wavelength increases, the number of oscillations will decrease

Front 15

Why shouldn't you hold tube when taking Xrays?

Back 15

There is always leakage radiation

Front 16

EMR travels in all directions from its source T or F?

Back 16

True

Front 17

What produces more ionization short waves or long waves?

Back 17

the shorter the wavelength the more energy it has and the more chances it can cause ionization in the body and be helpful and harmful

Front 18

Why is EMR not harmful to us?

Back 18

because it is non ionizing (not enough energy to ionize)

Front 19

Properties of Xrays

Back 19

-packets of energy
-no electric charge
-travel in straight lines, but always diverging-IMAGE IS ALWAYS MAGNIFIED
-able to ionize
-highly penetrating
-range of wavelengths

Front 20

Principles of X-ray production

Back 20

x-rays are produced when the electrons are moving at very high speeds

-Electrons moving at very high speed either interact with nucleus or another electron to produce radiation

Front 21

What is Characteristic Radiation

Back 21

electrons hit other electrons

the binding energy of different shells are all different

because there are different interactions there is heterogenous x-rays

Front 22

Quantum theory

Back 22

photons

Front 23

Red spectrum

Back 23

low freq but large wavelength

Front 24

Blue spectrum

Back 24

High Freq but low wavelength

Front 25

Xray range of wavelength?

Back 25

.1 TO .5 ANGSTROMS

Front 26

What is Bremsstrahlung radiation?

Back 26

Produced when electrons moving at high speed come close to another material-nucleus with a high Z number

Front 27

X-ray tube-production of x-rays

Back 27

to produce the electron you need to heat the tungsten filament at a low voltage
-the electrons come out from the shells and produce the electron cloud-thermoionic electron cloud formation
-heat with low voltage-because of this you convert a 110 V to a low volt like 8-10 using a step down transformer
-then you have to move the e- at high speed-so you need a high potential difference between the cathode and anode and the electrons will be accelerated to half the speed of light—use a STEP UP transformer

Front 28

What entails electron focusing

Back 28

all negative charged so they all try to repel each other

the smaller the anode the better images, effects the sharpness of the image

more than 99% of the energy is turned into heat only 1% is radiation

Front 29

Electron to nucleus interaction:

Back 29

Bremsstrahlung

Front 30

Electron to electron interaction

Back 30

Characteristic radiation

Front 31

Because so much heat is generated what is used that has a high melting point?

Back 31

Tungsten-ANODE

Front 32

high atomic number, low vapor pressure and low degree of thermal conductivity

Back 32

Tungsten

Tungsten is embedded in a copper shell

Front 33

tungsten disadvantage

Back 33

Not the most efficient conductor

Front 34

How are Xrays produced?

Back 34

When high velocity electrons suddenly decelerate due to high Z # of nuclei in an absorbing material

Front 35

What is the function of filtration?

Back 35

Xrays hit filter first. The filtration removes the low energy radiation

Low energy Xrays get absorbed in the skin and only increase the radiation dose but don’t help in imaging

Front 36

What is the function of aluminum in Filtration?

Back 36

Helps filter low energy radiation. The right amount of aluminum depends on the KvP of the tube

Front 37

Amount of Aluminum needed for 50-70 Kvp:

Back 37

1.5 mm aluminum

Front 38

Amount of Aluminum needed for Kvp above 70:

Back 38

2.5 mm aluminum

Front 39

How does using aluminum filtration help with respect to time of exposure?

Back 39

Aluminum filtration decreases patient skin exposure but compensate b increasing the time of exposure

Front 40

70% of diagnostic x-ray beam is Bremsstrahlung T or F?

Back 40

T

Front 41

total energy that is contained in the beam

Back 41

intensity

Front 42

Amount of Aluminum needed for 50-70 Kvp:

Back 42

1.5 mm aluminum

Front 43

Amount of Aluminum needed for Kvp above 70:

Back 43

2.5 mm aluminum

Front 44

Amount of Aluminum needed for 50-70 Kvp:

Back 44

1.5 mm aluminum

Front 45

Amount of Aluminum needed for Kvp above 70:

Back 45

2.5 mm aluminum

Front 46

Total energy that is contained in the beam?

Back 46

Intensity

Front 47

How is the electron cloud produced?

Back 47

Current heats tungsten filament to Approx. 2200C. Thermal energy causes outer shell e- to form electron cloud

Front 48

Before generating the elctron cloud how many volts go into the primary & secondary coil

Back 48

110 volts = primary

8-12 volts = secondary

Front 49

Exposure time only affects the QUANTITY-amount of photons. T or F?

Back 49

True

Front 50

What will exposure time affect?

Back 50

Quantity of Xrays but not contrast (quality)

Front 51

quantity will be less but the quality will be increased

Back 51

Filtration

Front 52

What shapes the beam because x-rays tend to go different directions, and makes the beam parallel?

Back 52

Collimation

Front 53

When a voltage difference is applied between the cathode and anode what happens?

Back 53

Electrons are accelerated to approx. 0.5 X speed of light

Front 54

Why do you place the tube as close as possible to the patients face?

Back 54

reduce radiation to rest of face

Front 55

inverse square law?

Back 55

-in the intensity of radiation is 8” is 400 then at 16” what is it100

-if it is 9” is 100 then what is it at 3”36 (change the 81 to 100)

Front 56

What is the focusing cup made of?

Back 56

Molybdenum focusing cup is located at the cathode

Front 57

Cathodes and Anodes are found where?

Back 57

Xray tube = site of xray production

Front 58

Inherent filtration?

Back 58

Glass & oil of tube

Front 59

Total filtration =

Back 59

Aluminum + inherent filtration

Front 60

Reduces the intensity of electron beam

Back 60

filtration

Front 61

The thickness of aluminum (in mm) which will give the same filtration as the inherent filtering material (glass and oil) of x-ray tubehead under the same conditions of irradiation

Back 61

Aluminum Equivalent

Front 62

What increases exposure time but decreases patient skin exposure?

Back 62

Total filtration

Front 63

High contrast

Back 63

SHORT GRAY SCALE

Front 64

low contrast

Back 64

LONG GRAY SCALE

Front 65

Although filtration requires as increase in exposure time up to 50% to compensate for loss of intensity, it reduces patient skin exposure by as much as

Back 65

80%

Front 66

why do you have a long gray scale at 100 vs. 40 kvp

Back 66

there is a higher energy so you can get more shades

Front 67

The intensity of radiation varies inversely as the square of what?

Back 67

Source film distance

Front 68

In dentistry, an increase of 15 kVp usually requires halving the exposure time, and a decrease of 15 kVp necessitates doubling the exposure time to maintain the same density (darkness) on the radiograph. T or F

Back 68

T

Front 69

mAs determines what?

Back 69

the total number of x-ray photons produced in the beam

Front 70

Intraoral periapical film have better resolution than panoramic radiographs. T or F

Back 70

T

Front 71

Which type of raqdiograph has better resolution, Intraorals or Pano?`

Back 71

Intraoral: 9-12 line pairs/mm.

Panoramic: 3-5 lp/mm.

Front 72

The ability of a radiograph to define an edge precisely (DEJ)

Back 72

sharpness

Front 73

Where in the Atom are Xrays produced

Back 73

Outside the nucleus of stable atoms

Front 74

Where in an atom are gamma rays produced

Back 74

inside the nucleus of radioactive atoms

Front 75

What 3 shells are important in generating an XRAY?

Back 75

KLM

This are the one most tightly bound

Front 76

What particle ionizes tissue quickly and is low penetrating?

Back 76

Alpha and Beta Particulate EMR

Has enormous electric charge and mass that quickly ionizes tissue.

Front 77

Can an XRAY knock off an orbital eletron?

Back 77

Yes

By doing so it ionizes that atom. This happens at a lower rate that particulate radiation

Front 78

What causes the electrons to be fired from the cloud?

Back 78

high voltage potential

Front 79

What is the Benson Line Focus Principle?

Back 79

20 degree bend in Anode creates a smaller effective focal spot

Front 80

interaction of high speed electrons with the atom of Tungsten is referred to as?

Back 80

Brems Radiation

Can consist of atom stop electron and producing XRAY or by direct collision of the atom with the electron.

Front 81

K shell electron is bumped off by electron. L shell electron slides down producing a weak 59KeV photon. This is called?

Back 81

Characteristic Radiation

Front 82

intensity?

Back 82

number of XRAYs

Front 83

Radiation type that is heterogenous?

Back 83

Brems

This means it produces XRAYS with different KvP

Characteristic tends to produce a 59 and 9 KvP

Front 84

Increasing KvP increases what?

Back 84

number and energy of xrays

Front 85

What is KvP?

Back 85

Max voltage applied across the tube (cathode to anode). The greater the difference AKA 100 the more likely you are to produced a high KeP electron

Front 86

What is KeP?

Back 86

the energy of one electron in the beam

Front 87

Why is KvP not always equal to KeP

Back 87

because the voltage across the tube is variable pulsating at 60 cycles per second (0 Kvp to 100 KvP). When the electron hits the Anode the potential may not necessarily be at 100 Kvp.

Front 88

Qaulity of Xrays is determined by

Back 88

kV

Front 89

Quantity of Xrays is determined by?

Back 89

Exposure Time & mA

Front 90

Shell with weakest binding energy?

Back 90

Q

Front 91

Can xrays be focused to a point?

Back 91

No. We can only try

Front 92

Increasing distance by 2 affects intensity how?

Back 92

decreases it by 4

Intensity = 1/distance ^2

Front 93

high contrast results in

Back 93

short gray scale

Front 94

Low contrast =

Back 94

Long gray scale

Front 95

Refers to the ability to record separate images of small objects which are placed very close together

Back 95

Resolution

Front 96

The ability of a radiograph to define an edge precisely (DEJ)

Back 96

Sharpness

Front 97

What 2 things are affected most by KvP, mA, Time, Distance and Film type?

Back 97

Contrast and Density