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Biological Systems II > Radiation Physics > Flashcards

Radiation Physics Flashcards

1
Q

An x-ray is an ____ beam or photon of energy. ____

A

invisible

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2
Q

Image receptor is the material on which the ____ is created. This may be a film, fluoroscope, or a digital receptor. The receptor is processed (chemically or digitally), and a radiograph is made.

A

latent image

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3
Q

X-Ray Machine
X-Ray tube is positioned within the tube head with some components of the power supply

Tube may be ____ within the tube head to ____ the radiographic image quality

A

recessed

improve

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4
Q

Coolidge Tubes
Basic design introduced in ____ Composed of
-Anode
-Cathode – source of ____
-____ glass tube
Electrons from cathode strike ____, producing x-ray photons

A

1913
electrons
evacuated
anode

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5
Q

Coolidge Tubes
􏰀 Requires power supply to:
Heat the ____ to generate electrons

Establish a ____ potential between the anode and the cathode to ____ the electrons

A

filament
high-voltage
accelerate

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6
Q

Cathode Features

􏰀 ____ – source of electrons within the x-ray tube

A

filament

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7
Q

Cathode
􏰀 Filament (source of electrons)
Coil of ____ wire ____ long and ____
in diameter
Mounted on 2 ____ for support and carrying electric current
Wires connect to ____ and ____ voltage electric sources
____ of the wire causes the release of electrons (boiling off of electrons)

A 
tungsten
1 cm
0.2 cm
stiff wires
high
low
incandescence
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8
Q

Focusing cup – ____ charged concave reflector (charge repels electrons)

A

negatively

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9
Q

Cathode
____ or ____ focusing cup – directs the electrons produced by the filament toward the ____ on the anode

Electrons travel from cathode to anode
by repellent forces on the ____ cathode and attractive forces on the ____ anode

A

nickel
molybdenum
focal spot

negatively charge
positively charged

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10
Q

Anode
____ embedded in ____ stem
Converts the kinetic energy of electrons from the filament into ____
Inefficient process – ____ of energy is lost as heat

A

tungsten target
copper stem
photon energy (x-rays)
99%

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11
Q

Tungsten (W)
High ____ (____)
Most efficient in producing x-rays

High \_\_\_\_ (\_\_\_\_0oC)
Helps withstand the high temperatures produced during the generation of photons

High ____
Dissipates heat into the copper stem

Highest melting point of any ____

Low ____
Helps maintain the vacuum in the tube at high operating temperatures

A 
atomic number
74
melting point
337
thermal conductivity
metal
vapor pressure
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12
Q

Tungsten Target
Embedded in a large block of ____ (a good thermal conductor)
􏰘 Dissipates heat from the tungsten – reduces risk of target ____

____ surrounds the x-ray tube
Stationary anode

A

copper
melting
insulating oil

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13
Q

Focal Spot
Area on target where focusing cup ____ electrons from the filament

Sharpness of radiographic image ____ as the size of the focal spot ____

A

directs
increase
decreases

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14
Q

Focal Spot
Heat generated ____ as the size of the focal spot ____

Target is angled to ____ effective focal spot size while ____ distribution of electrons over a large target

Projection of focal spot is ____ to the electron beam (effective focal spot is ____ than the actual focal spot)

A

increases
decreases

decrease
maximizing

90 degrees
smaller

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15
Q

Production of X-rays
____ heats the filament of the cathode, releasing electrons – ____

Higher temperatures produce more ____

Electrons ____ from the cathode to the tungsten target on the anode

X-rays are produced as the electrons ____ or ____

A 
current
thermionic emission
free electrons (electron cloud)
accelerate
decelerate
stop
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16
Q

Electric Circuits
􏰘 Electric current is the ____ of electrons through a conductor
􏰘 Rate of flow (electrons/second past a set point) is measured in ____
􏰘 Depends on ____ and ____ of the conductor to flow, measured in____
􏰘 Ohm’s law: V = IR, V=potential, I=current, R=resistance

A 
movement
amperes
voltage
resistance
ohms
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17
Q

Power Supply
􏰘 Heats the filament using ____ current to generate electrons

􏰘 Establishes a ____ between the anode and the cathode to ____ the electrons

A

low-voltage
high-voltage potential
accelerate

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18
Q

Power Supply(Electric Circuits)
􏰘 Tube ____ (mA) -Amperes are capitalized
􏰘 Tube ____ (kVp) -Volts are capitalized
􏰘 Together, mA and kVp determine the ____ of the x ray beam, along with the ____ and the ____ used

A 
current
voltage
intensity
target material
filtration
19
Q

Tube Current (mA)
􏰘 Determines the ____ produced
􏰘 The higher the mA, the greater the number of ____ generated, and consequently, more x rays produced
􏰘 ____ is the flow of electrons from the filament to the anode, then ____ to the filament through wiring of the power supply

A

number of electrons
electrons
tube current
back

20
Q

Tube Current (mA)
􏰘 Filament step-down transformer reduces voltage of the ____ to ~ ____
􏰘 Controlled by the ____ , adjusting ____ and ____ through the low- voltage circuit
􏰘 Regulates ____ of the filament and number of electrons ____

A 
alternating current (AC)
10V
mA switch
resistance
current
temperature
emitted
21
Q

Tube Voltage (kVp)
􏰘 Requires ____ between the anode and the cathode to generate x rays
􏰘 ____ converts the primary voltage from the input source to the ____ voltage
􏰘 ____ provides the high voltage required by the x-ray tube to accelerate electrons from the cathode to the anode

A

high voltage
autotransformer
secondary
high voltage transformer

22
Q

Tube Voltage (kVp)
􏰘 Peak voltage of the incoming line current is boosted to ____ kV
􏰘 Boosts peak energy of the electrons to 60 to 100 keV
􏰘 Line voltage is ____(alternating current), so intensity is greatest at peak of each ____ of the cycle
􏰘 No x-rays are generated during the ____ portion

A

60 to 100
variable
positive portion
negative

23
Q

Tube Voltage (kVp)
􏰘 kVp determines the ____ of the electrons that generate the ____ from the target
􏰘 kVp determines the ____ (quality) of the x rays produced
􏰘 For tungsten targets, at least ____ must be used to produce the
􏰘 ____radiation

A 
energy
photons
maximum energy
70 kVp
k-characteristic
24
Q 
Half-Wave Rectification
􏰘 AKA \_\_\_\_
􏰘 Limits x-ray production to \_\_\_\_ of the AC
cycle
􏰘 Almost all dental x-ray units are \_\_\_\_
A

self-rectification
half
self-rectified

25
Q

Filtration
􏰘 Removes ____ photons (____ wavelength)
􏰘 Accomplished with an ____ filter placed in the path of beam
􏰘 Preferentially removes ____ photons

A

low energy
long
aluminum
low energy

26
Q

Inherent Filtration
􏰘 Consists of materials in ____ of the photon beam from the ____ to the point of ____ the x-ray head
􏰘 These include
____ of the tube
____
____ surrounding oil
􏰘 Ranges from ____ mm aluminum equivalent

A 
path
focal spot
exiting
glass wall
insulating oil
barrier
0.5 to 2.0 mm
27
Q

Total Filtration
􏰘 Sum of ____ and added ____ filtration
􏰘 External filtration consists of ____ discs placed over the exit port of the tube head
􏰘 Federal regulations require ____ aluminum equivalent for beams up to 70 kVp and ____ for beams over 70 kVp

A 
inherent filtration
external
aluminum
1.5 mm
2.5mm
28
Q

kV

increase >80
decrease 60-70

A

density:
increased (darker)
decreased (lighter)

contrast
low
hight

29
Q

mA

increase
decrease

A

density:
increased (darker)
decreased (lighter)

contrast:
no effect

30
Q

exposure time

increase
decrease

A

density:
increased (darker)
decreased (lighter)

contrast:
no effect

31
Q

filter thickness

increase (thicker)
decrease (thinner)

A

density:
decreased
increased

contrast:
decreased
increased

32
Q

target-detector distance

increase
decrease

A

density:
decreased
increased

contrast:
no effect

33
Q 
Control Panel
􏰘 Controls power supply to the tube head
􏰘 Controls number of \_\_\_\_ generated (the exposure time)
􏰘 Controls the \_\_\_\_
􏰘 Controls the \_\_\_\_
A

impulses
kVp
mA

34
Q

Tube rating and Duty Cycle
Tube rating: Maximum exposure time the tube can be energized without risk of damage to the target from ____.This should be posted at the ____
Duty Cycle: Frequency with which ____ can be made.
heat units(HU)= kVp x mA x sec dental diagnostic tubes < ____

A

overheating
machine

successive exposures
20 KHU

35
Q 
COHERENT SCATTERING (Classic/Thompson scatter)
May occur when a low-energy incident photon (less than \_\_\_\_) passes near an outer electron of an atom (which has a low binding energy). The incident photon interacts with the electron by causing it to become momentarily excited at the same frequency as the incoming photon The incident photon ceases to exist. The excited electron then returns to the ground state and generates another x- ray photon with the same frequency and energy as in the incident beam. This interaction accounts for only about \_\_\_\_of the total number of interactions (per exposure) in a dental examination.
A

10 keV

8%

36
Q

PHOTOELECTRIC ABSORPTION
Photoelectric absorption is critical in diagnostic imaging. This process occurs when an ____ photon collides with a ____ electron in an atom of the ____ medium. At this point the incident photon ceases to exist. The electron is ejected from its shell and becomes a ____ About ____ of the photons that are absorbed from a dental x-ray beam are absorbed by this process

A 
incident
bound
absorbing
recoil electron (photoelectron)
30%
37
Q

COMPTON SCATTERING
Compton scattering occurs when a photon interacts with an ____ electron About ____ of the photons that are absorbed from a dental x-ray beam are absorbed by this process. In this interaction the incident photon collides with an ____, which receives kinetic energy and recoils from the point of impact. The path of the incident photon is deflected by its interaction and is scattered from the ____ of the collision.

A

outer orbital
62%
site

38
Q

Roentgen [ Air Kerma=expressed as ____ that replaced ____]
Rad [ Absorbed dose 1 rad = 100 ergs/gram, 1 Gy = ____]
Rem [ Equivalent dose is absorbed dose averaged over tissue or organs and the radiation weighting factor]
Gray [ 1 Gy = ____]
Sievert [ 1 Sv = ____]
Kerma = ____ released in matter

A 
Gy
roentgen
100 rads
100 rads
100 rems
kinetic energy
39
Q

Effective dose (E) is used to estimate the risk in humans. It is the sum of the products of equivalent dose to each ____ or ____ and the ____:

E sum(WT X HT)

Unit of effective dose is the ____)

The tissue weighting factors include gonads, ____; red bone marrow, ____; esophagus, ____; thyroid, ____; skin, ____; and bone surface, ____

A

organ
tissue (Ht)
tissue weighting factor (Wt)

sievert (Sv)

  1. 20
  2. 12
  3. 05
  4. 05
  5. 01
  6. 01
40
Q

Heat the filament longer > produce more e- > stronger ______

A

beam

41
Q

two _____; three _____

A

circuits

transformers

42
Q

If mA and kVp are fixed, you can alter the __________

A

exposure timing

43
Q

HVL = _______ = _______

A

half value layer

aluminum

44
Q

Collimators are usually made of ______

A

lead

Biological Systems II (5 decks)

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