Quiz 1 Flashcards
(112 cards)
1
Q
What is the definition of radiation?
A
It is the transmission of energy through space and matter.
It can be ionizing or non-ionizing depending on the amount of energy in the radiation.
2
Q
Which type of radiation is considered ionizing?
A
UV rays, x-rays, and gamma rays
3
Q
What is the definition of ionizing radiation?
A
Radiation with sufficient energy to displace atomic electrons. It can lead to cell death and molecular alteration
4
Q
What constitutes the largest percentage of natural radiation?
A
Radon radiation at 37%
5
Q
What constitutes the largest percentage of man-made radiation?
A
CT scans 24%, medical x-rays and nuclear medicine 12%
6
Q
What are the two types of ionizing radiation? And what kind of cells/particles belong in them?
A
Particulate Radiation - Alpha, beta particles, and neutrons Electromagnetic radiation (photons) - gamma and x-rays
7
Q
! Which of the following is not a form of ionizing radiation? ! A) xrays ! B) microwaves ! C) gamma rays ! D) ultraviolet wavelength light
A
B
8
Q
In terms of units of measurement for radiation, which type is used on boards?
A
SI units
besides SI units, there are traditional units and you can convert between the two
9
Q
What are the units for radiation exposure?
A
Coulomb/kilogram (C/kg)
10
Q
What are the units for absorbed dose?
A
Gray (Gy)
11
Q
What are the units for equivalent dose, and effective dose?
A
Sieverts (Sv)
12
Q
What are the units for radioactivity?
A
Becquerel (Bq)
13
Q
What does the measurement of radioactivity tell us?
A
It tells us the decay rate of a radioactive material. Measured in Bq
14
Q
What is the definition of radiation exposure?
A
It is a measurement of radioactive kinetic energy emitted from a source, and is quantified generally by its capacity to ionize air. It’s measured in C/kg
15
Q
What is the definition of air kerma?
A
The amount of electrical charge produced by ionizing radiation per mass of air. Has to do with radiation exposure because it is measured in C/kg
16
Q
What is absorbed dose?
A
It is the energy absorbed by any type of matter, and is derived by calculating the imparted energy divided by the mass absorbing it. Units are Gy, or greys
17
Q
What is equivalent dose?
A
It is used to compare the biologic effect on a tissue from different types of radiation. Units are Sieverts (Sv). Equivalent dose is dependent on Linear Energy Transfer (LET), which varies depending on the type of radioactive energy. Particulate radiation has higher LET than photons, thus a greater biologic effect.
18
Q
What is effective dose?
A
It is used to measure the estimated risk to humans. Units are Sieverts (Sv). It takes into account the effects of different types of radiation and radiosensitivity of different tissues.
19
Q
Which tissues are most sensitive, or in other words, which tissues have the highest weighting factor, which is used to calculative effective dose?
A
Bone marrow Breast Colon Lung Stomach
20
Q
The reason we may wish to cover the reproductive organs of a patient when taking radiographs can best be explained by the concept of: A) Equivalent Dose B) Linear Energy Transfer (LET) C) Effective Dose D) Radioactivity
A
C
21
Q
What is the definition of radiobiology?
A
The study of the effects of ionizing radiation on living systems
22
Q
When it comes to radiation chemistry, what is a direct effect?
A
When a photon or secondary electron ionizes biologic macromolecules.
Photon + RH = R* + H* + e-
The free radicals can then go on to cause havoc
Direct Effect accounts for 1/3 of biologic damage from x-rays. (more common effect with particulate radiation)
Altered molecules have different chemical and biologic properties that may lead to cell death, mutation or carcinogenesis
23
Q
When it comes to radiation chemistry, what is the radiolysis of water?
A
It is a photon absorbed by water in an organism, which ionizes water molecules into free radicals.
Photon + H20 = H* + OH*
And these free radicals can join O2 to form hydrogen peroxide and hydroperoxyl and cause damage
24
Q
When it comes to radiation chemistry, what is an indirect effect?
A
This is free radicals and toxins produced through the intermediate step of water radiolysis that interact with biologic macromolecules to cause changes. For example, Hydrogen and hydroxyl free radicals are formed from radiolysis of water, which then interact with organic molecules
RH + OH. = R. + H2O
Indirect Effect involves radiolysis of water as precursor to biologic damage, and accounts for 2/3 of biologic damage from x-rays.
25
What is the primary cause of radiation-induced cell death?
Damage to the DNA. This happens due to breakage of one or both DNA strands, cross-linking, change or loss of base
26
```
The presence of which of the following does not contribute to the indirect effect of ionizing radiation on altering DNA?
! A) water (H2O)
! B) oxygen (O2)
! C) photons
! D) hydrogen peroxide (H2O2)
```
D
27
When it comes to classification of cellular changes, what is the deterministic effect?
Radiation injury is dependent on the dose.
Requires higher level of exposure to produce clinically observable effect.
There is an exposure threshold below which the effect does not occur or is not observable.
Deterministic effects are generally tissue-related.
Fibrosis and hematopoietic damage are clinical manifestations.
28
Where are short term effects of radiation seen?
In tissues that have rapidly dividing cells, like the mouth, GI tract, and bone marrow.
29
Where are long-term effects of radiation seen?
Loss of parenchymal cells and replacement by fibrous connective tissue. Loss of capillary function so loss of oxygen transport, waste removal, and nutrient transfer
30
What are some of the modifying factors of the deterministic effect?
Dose, dose rate, oxygen levels, and LET. As all of them increase, damage increases.
31
Which organs have high, medium, and low radiosensitivity?
High - lymphoid organs, bone marrow, GI tract
Medium - vasculature, salivary glands, kidney, liver
Low - Optic lens, muscle
32
What are the oral manifestations of irradiation?
Loss of taste, mucositis, hyposalivation, radiation caries, trismus, osteoradionicrosis
33
When it comes to classification of cellular changes, what is the stochastic effect?
Radiation injury based on the probability of occurrence.
The probability of the effect occurring increases with dose.
There is no threshold level, and there is no level of exposure at which there is no risk.
Sublethal damage to DNA
34
When taking a single periapical radiograph on a patient you can assure them that the exposure is so low that there is absolutely no risk of long term damage.
! A) True
! B) False
B
35
What is the average annual effective dose of ionizing radiation - Natural?
2.4 microsieverts
36
What is the average annual effective dose of ionizing radiation - Man-Made?
2.5 microsieverts
37
How many dental x-rays does it take to reach the level of radiation given off by one chest CT scan?
1400
38
! You are preparing to take a digital panoramic radiograph on a patient, but the patient is concerned about the amount of radiation they might be receiving and the long term risk. You try to allay their fear by comparing it to which of the following:
! A) 3 days of exposure to normal background radiation (exposure)
! B) Flying round trip from SLC to New York (risk)
! C) Driving to Saint George (risk)
! D) All of the above
D
39
What does ALARA stand for?
As low as reasonably achievable
40
There are no dose limits in diagnostic and therapeutic radiology? True or False?
True. Dose limits are used to limit exposure in industrial and occupational settings.
41
We should never take radiographs on pregnant patients. True or False?
False. We should never take routine radiographs on them, but if it is necessary, then we can take precaution while doing it.
42
What type of film speed should we use and why?
Use E and F film speed. High film speed requires less radiation to expose. D is an old one that requires more. Digital is best though.
43
What is an intensifying screen?
It is a screen that contains rare earth elements that give off light photons when struck by xrays. These light photons then act to expose the underlying film, rendering a properly exposed film with less radiation.
44
Does a shorter or longer distance reduce exposure?
Longer distances reduce exposure. Going from 8" to 16" reduces exposure by 10-25%
45
How much do rectangular collimators reduce area of exposure by in comparison with circular?
60%
46
What does the xray beam filter do?
It removes lower energy, easily absorbed photons from the beam.
47
How far away should you stand from the radiation source?
At least 2 meters, or 6 feet.
48
At what degree should we be positioned from the primary xray beam?
90-135 degrees
49
What are some things that comprise the tube head?
Metal housing, power supply (transformers), oil, filter, collimator, xray tube, and aiming cylinder
50
What is safer, high or low energy x-rays?
Higher, because the lower ones are the ones that are absorbed into our skin.
51
What is bremsstrahlung radiation?
Most dental x-rays are bremsstrahlung. The negative electron coming in is attracted to the positive nucleus. You want higher protons and neutrons in the nucleus when dealing with x-rays. Bremsstrahlung radiation is Created when high-speed electrons interact with tungsten nuclei in the target, resulting in a spectrum of x-rays with different energies. This accounts for the bulk of x-ray photons produced.
- High Energy – Some electrons directly collide with a nucleus, producing a high energy photon (in keV) that is equal in energy to the incident electron.
- Medium Energy – Produced by electrons passing close to the nucleus causing deflection and deceleration of the electron. This deceleration causes the electron to lose some of its energy in the form of photon radiation.
- Low Energy – Produced when electrons pass at a distance from the nucleus. They are deflected and slowed somewhat, producing a low energy photon.
- Resulting x-ray energy spectrum will have a maximum equivalent to the energy being applied to the x-ray tube. So a 70kVp tube head will produce x-rays with a maximum of 70keV of energy.
52
What is characteristic radiation?
- This is when a high speed electron collides with an orbiting inner ring electron in the tungsten target, ejecting it from the orbit.
- An electron from the next energy ring jumps rings to fill the void, giving up a photon of energy equal to the difference in binding energy between the rings.
- The energy given up is “characteristic” for that target atom
- Accounts for only a small fraction of x-ray photons generated.
53
An incident electron directly striking a tungsten nucleus produces:
a. characteristic radiation
b. maximum energy Bremsstrahlung radiation
c. low energy Bremsstrahlung radiation
d. free electron
B
54
Is the cathode in an x-ray tube negative or positive?
It is negative
55
What does the cathode do in an x-ray tube?
A tungsten filament and molybdenum focusing cup provide the source and direction of electrons of the cathode ray. Low voltage is applied to heat the filament, producing a cloud of electrons through thermionic emission. The molybdenum focusing cup electrostatically focuses the electrons into a narrow beam.
56
What does the anode do in an x-ray tube?
The anode is +. The tungsten target and copper stem convert the kinetic energy of the electron stream of photons to x-rays and heat here.
57
How does the x-ray tube work?
Electrons come in through the cathode and hit the tungsten target. Tungsten is great because it fulfills a lot of requirements, like high atomic number, high melting point, high thermal conductivity, and low vapor pressure. The tube is a vacuum for several reasons. The focal spot is the point on the target where the stream of x-ray photons originates. Should be as small as possible for the best radiographs yet must be large enough to dissipate heat. Placing target at an angle provides a smaller effective focal spot for sharp images while maintaining a larger actual focal spot for heat dissipation.
58
A molybdenum focusing cup in an x- ray tube
a. narrows the beam of electrons
b. is located in the cathode
c. directs electrons toward the tungsten target
d. all of the above
D
59
What is the function of the low voltage tube current?
It heats the tube filament generating a stream of electrons between the cathode and anode.
60
What is the function of the high tube voltage?
Between the cathode and anode, it accelerates the electron stream to a level that x-rays can be produced
61
What are the three types of transformers and what do they do?
1. Step-down filament transformer. It reduces incoming voltage (110V) to approximately 3-5 volts needed to heat the filament.
2. Step-up transformer. It provides a large electrical force needed to propel electrons from cathode to anode. Increases voltage from 110V to 60-100kV
3. Auto transformer. It is controlled by the kVp dial on the control panel, this transformer varies the voltage to the step-up transformer to achieve the desired high energy kVp to the tube.
62
What is the most frequent source of malfunction in the x-ray tube?
It is filament burnout. The X-ray machine should be left ON during the day. Increased strain is put on the filament when it is repeatedly warmed and cooled, as occurs when it is turned OFF and ON continuously.
63
If you wish to increase the energy of the emitted x-ray beam, you would:
a. increase power to the high voltage step up transformer
b. increase power to the low voltage tube current
c. increase the size of the focal spot
d. all of the above
A
(B wouldn’t work because if you did that, it would increase the number of electrons, not necessarily their energy though)
64
The quantity of radiation is inversely proportional to the tube current (mA)?
False. It is directly proportional. As tube current (mA) is increased, more electrons are released to collide with the target. More collisions equals more radiation.
65
What will an increase in tube voltage (kVp) do?
It will increase the x-ray penetration of matter. Increasing the potential between the anode and cathode increases the energy of each electron when it strikes the target.
This increases efficiency of the conversion of electron energy into x-ray photons.
66
What is the function of filtration when it comes to x-rays?
Filtration absorbs low energy photons that would not reach the image receptor. Aluminum filters are used to absorb these low energy photons.
67
What is the function of a collimator?
It is a metal barrier used to reduce the size of an x-ray beam. It is located over the port of the x-ray head and is lined with lead to absorb stray photons. The collimator reduces some of the scatter radiation and the patient surface that is exposed.
68
The intensity of the x-ray beam is inversely proportional to the square of the distance between the source and the target. True or False?
True. This is called the inverse square law. The x-ray shoots out like a cone, and the farther away, the larger the cone is so the larger the area, and so the smaller the exposure. If the area is 9, then it would be 1/9th the exposure had it been 1 and 1.
69
You expose an x-ray and it comes out underexposed. How do you try to correct the exposure on a retake?
a. move tubehead back to increase focal distance
b. increase kVp on the control panel
c. increase exposure area by using a round collimator
d. increase exposure time
B and D would both work. With C, you would just increase the exposure area, but you wouldn't get more exposure.
70
What is coherent scattering?
It occurs when low-energy photons are deflected by outer ring electrons. Accounts for only about 7% of interactions in dental, so contributes very little to film fog on image.
71
What is photoelectric absorption?
This is the process in which incident photons are absorbed by an atom by interacting with inner shell electrons. This is what makes the lighter areas on the film, making radiographic imaging possible. These photons are absorbed in denser areas like metal and dentin, which end up opaque because they are absorbing!
72
What is compton scattering?
This occurs when a photon interacts with an outer orbital electron. This accounts for 49% of interactions in dental radiography. Scattered photons darken and degrade the image while carrying no useful information.
73
Which of the following photon interactions make it possible to produce radiographic images:
a. coherent scattering
b. photoelectric absorption
c. Compton scattering
d. all of the above
B
74
What does an X through a tooth mean when charting?
Black means it was congenitally missing and blue means that it was extracted.
75
How do you chart a composite filling, an amalgam filling, a gold restoration, and a porcelain crown?
Outline surfaces in blue
Fill in surfaces in blue
Cross hatch surfaces in blue
Outline tooth in blue
76
What are the 3 ways you can maximize sharpness and resolution (image clarity) with an x-ray?
1. Use as small an effective focal spot as practical (built into tube head)
2. Increase distance from focal spot to object with long open-ended cylinder (aiming cylinder)
3. Minimize the distance from the object (tooth) to the image receptor (the film)
77
What are the 2 ways you can minimize the image size distortion (magnification)?
1. Increase the distance from the focal spot to the image receptor.
2. Decrease the distance from the object (tooth) to the image receptor.
78
What are the 2 ways you can minimize the image shape distortion?
1. Position the image receptor (the film) parallel to the long axis of the object (tooth)
2. Orient the central ray (cone) perpendicular to the object and image receptor.
Image shape distortion can have the effect of foreshortening or elongation.
79
When does foreshortening (image shape distortion) take place?
This happens when the central beam is perpendicular to the image receptor, but not to the tooth.
80
When does elongation (image shape distortion) take place?
This happens when the central beam is perpendicular to the tooth, but not to the image receptor.
81
What is and what is the outcome of the bisecting-angle technique?
This is when the image receptor is flat against the lingual surface of the tooth, and the bisecting line that goes in between the long axis of the tooth and the image receptor is where you would but the central beam perpendicular to. The outcome is an image of the correct length, but with distortions of tooth and height of alveolar crest.
82
What does the SLOB rule stand for and when would we use it?
Same Lingual Opposite Buccal. This is used for determining if an object found on a radiograph is located
buccal, lingual or in the same plane as the teeth. You take a second x-ray but more medially and whichever way the object goes will tell you if the object is lingual or buccal to the tooth.
83
How can you increase periapical coverage on an x-ray if you need to?
Just tilt the head of the x-ray forward to increase the angulation a little bit.
84
How can you taken a proper x-ray on a patient who has a low palate?
You can shove a cotton roll below and above the biteblock to give some more height to work with.
85
To lessen distortion in a radiograph you can:
A) Increase distance between focal spot and image receptor
B) Decrease distance between object and image receptor
C) Use paralleling technique
D) All of the above
D
86
What does a full mouth series of radiographs consist of?
FMX = 18 films, 14 PA's, 4 BW's - #2 sensor for all radiographs
FMX = 21 films, 17 PA's, 4 BW's - #1 sensor for anteriors, #2 for everything else
- 2 bicuspid bitewing, 2 molar bitewing, 2 central incisors, 4 cuspids, 4 bicuspids, 4 molars = 18
87
When taking periapical radiographs of the upper bicuspids you do which of the following:
A) Position the cone parallel to the occlusal plane
B) Position the sensor such that it captures the cuspid back
to the first molar
C) Angle the cone from the mesial in order to project the
cuspid onto the sensor
D) Tip the patient back in the chair, mouth open, until the
mandible is parallel with the floor
B
88
What is the definition of radiolucent?
Any substance that permits the transmission of x-rays
89
What is the definition of radiopaque?
Any substance that blocks the transmission of x-rays
90
Is the lamina dura wider with people with heavy occlusion or soft occlusion?
With heavy occlusion. It is very thin in people with teeth not subject to function. The lamina dura is radiopaque, just like dentin and enamel.
91
With anterior teeth, is the alveolar crest flat or pointed?
It is pointed with anterior teeth and with posterior teeth it is flat and parallel to a line connecting the CEJ's of adjacent teeth. The alveolar crest is radiopaque.
92
The pulp and the periodontal ligament are both radiopaque. True or false?
False. They are radiolucent.
93
Which type of restorative materials are radiolucent?
Silicate cements, some composite resins, and porcelain.
94
```
This portion of the tooth makes up the bulk of the structure of the tooth and is about the same opacity as bone:
A) Enamel
B) Dentin
C) Cementum
D) Pulp
```
B
95
When looking at the posterior jaw, label in order the three things from top to bottom that you could see on an x-ray.
Mylohyoid ridge
Submandibular gland fossa
External oblique ridge
96
What is the largest source of natural radiation?
a. cosmic radiation
b. radon
c. xrays
d. solar radiation
B
97
For a given amount of radiation exposure to each organ, which organ would receive the greatest effective dose?
a. breast
b. bladder
c. skin
d. brain
A
98
When considering the stochastic effects of radiation exposure, which of the following is not true?
A. The risk of injury is based on probability.
B. The greater the dose, the greater the chance of injury.
C. There is a threshold level above which injury will certainly occur.
D. Injuries primarily due to DNA damage
C
99
When taking intraoral radiographs with conventional tube heads the operator should stand at least how far from the X-ray source?
A. 2 meters
B. 3 feet
C. 15 feet
D. It doesn't matter
A
100
When trying to reduce radiation exposure to both patients and operators which of the following does not reduce necessary exposure?
A. rectangular collimation
B. ALARA
C. thyroid collars
D. slow speed film
D
101
Characteristic radiation is produced when an incident electron:
A. collides with a tungsten nucleus
B. passes near a tungsten nucleus
C. collides with an orbiting inner ring electron
D. all of the above
C
102
In an X-ray tube the cathode
A. is positively (+) charged
B. contains the tungsten filament
C. contains the tungsten target
D. is copper
B
103
The most frequent source of malfunction in an X-ray tube is
A. filament burnout
B. easily avoided by turning the machine off between patients
C. degradation of the tungsten target
D. shorting of low voltage transformer
A
104
Increasing tube current (mA) to the X-ray tube head does which of the following:
A. increases energy of the incident electrons
B. decreases the radiation dose to the patient
C. Increases the number of incident electrons
D. none of the above
C
105
An incident photon is absorbed while interacting with inner shell electrons of an atom resulting in:
A. Bremsstrahlung radiation
B. Compton scattering
C. Coherent scattering
D. Photoelectric absorption
D
106
When charting dental restorations, existing composite resin fillings are depicted how?
A. Surfaces outlined in blue
B. Surfaces outlined in red
C. Surfaces outlined then colored solid blue
D. Surfaces outlined and then crosshatched in red
A
107
A foreign object is observed at the apex of tooth #29. You retake the radiograph by angling the tube head from the mesial. The resulting radiograph shows the object moved mesial to its former location. Which of the following is true regarding the position of the foreign object?
A. The object is in the same plane as the root of #29.
B. The object is buccal to #29.
C. The object is lingual to #29.
D. None of the above.
C
108
In a full mouth series of X-rays, a diagnostic quality radiograph of the maxillary bicuspids must include all but which of the following?
A. Distal of the cuspid.
B. Apex of both bicuspids
C. Mesial of first molar
D. Mesial of second molar
D
109
When examining a radiograph you would expect which of the following to show up as the lightest material on the radiograph?
A. Enamel
B. Cortical bone
C. Amalgam
D. Composite resin
C
110
On a maxillary molar periapical radiograph it is common to see which of following?
A. maxillary sinus
B. nasal cavity
C. mental foramen
D. genial tubercle
A
111
What are the two names for the hole in the chin?
Genial tubercle and lingual foramen. The mental foramen is off to the sides. You can also see the mandibular canal where the nerves run from the far sides.
112
What are the three guiding principles to radiation safety?
1. Justification
2. ALARA
3. Dose limitation
