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Oral Radiology > Final Exam > Flashcards

Final Exam Flashcards

(183 cards)

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1
Q

Stochastic effects

A

Cell DNA injury
No threshold
-All or non response

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2
Q

In stochastic effects the greater the does

A

Increases the probability of occurrence

Any amount of radiation

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3
Q

Deterministic effect

A

High amount of radiation

  • Increased cell death
  • Threshold does
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4
Q

Threshold dose

A

(Deterministic effect)

Clinical symptoms apparent at any dose above threshold

Severity is PROPORTIONAL to dose

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5
Q

2 types of effects from formation of free radicals

A

Direct effects

Indirect Effects

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6
Q

Law of Bergonie and Tribondeau

A

Radiosensitivity of different tissues

  • Amount of undifferentiated cells
  • Mitosis activity
  • Length of active proliferation

Oocytes and lymphocytes

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7
Q

What cells have the highest radiosensitivity

A 
Lymphoid tissues
Bone marrow
Testes
Ovaries
Small intestines
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8
Q

The more undifferentiated the more

A

Mitosis and more radiosensitive tissue that is

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9
Q

Oocytes and lymphocytes are highly _______ but very _____

A

Differentiated

Sensitive

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10
Q

Linear Energy Transfer

A

The rate at which energy from photons is imparted as they travel through matter

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11
Q

High LET

A

Densely ionizing

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12
Q

Low LET

A

Sparsely ionizing

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13
Q

As energy is given off

A

Different damage is done

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14
Q

Absorbed Dose

A

Measure of the total energy transferred from any type of radiation to matter

rad or Gy

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15
Q

100 rads =

A

1 Gy

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16
Q

Equivalent Dose

A

Measure of how different types of radiation affect various tissues
-Sv

Radiation sighting factor (Wr)

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17
Q

1 Sv=

A

1 Gy

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18
Q

Effective Dose

A

Measure of estimated risk in humans
-Sv

Tissue weighting factor (Wt)

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19
Q

Acute Radiation Syndrome

A

Whole Body irradiation

Onset is ore rapid and severity increases with greater dose

Management depends on stage

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20
Q

Mucositis

A

Second week of therapy

Erythematous mucosa
Sloughing of the irradiated tissue
Painful
Secondary infection
Difficulty consuming food
Heals within 2 months after completion of radiotherapy
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21
Q

Xerostomia

A

Parenchuymal cells of salivary glands are radiosensitive

Reduced salivary flow

Pain/tenderness
Difficulty chewing and swallowing
May resolve in 6-12 months

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22
Q

Taste Loss

A

Second/third week of therapy
Reduced salivary flow my a contributing factor

Reversible

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23
Q

Trips us

A

Inflammation and fibrosis of musculature

Limited opening 2 months after completion of radiation therapy

PT

MOM affected

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24
Q

Radiation Caries

A

Rampant tooth decay
-mostly due to salivary gland changes

Maintenance and compliance
-daily fluoride varnish

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25
Impeded Tooth Development
``` Children receiving radiotherapy -Incompletely formed teeth —root development -Malformed teeth -Tooth bud destruction -Microdontia ``` Restorative procedures
26
Osteoradionecrosis
50-60 Gy Reduction of blood supply bone remolding capacity and mineralization breakdown of oral mucosa Mandible>maxilla Debridemtn Resection Restorative procedures Pre-Radiotherapy clearance when possible
27
Is radiation induced cancer a stochastic effect of radiation?
True; even one does of radiation can cause cancer. More doses increase risk but the end result does not change
28
All electromagnetic radiation can cause carcinogneis
False
29
The closer to the nucleus the higher the
Bonding energy
30
Highest bonding energy shell
K
31
Lowest bonding energy shell layer
P
32
Z number
(Atomic number) of protons Same number of electrons in a neutral atom
33
A number (Atomic mass #)
of P+N
34
The binding energy of electrons in a specific end shell is higher in an element with
A high Z number
35
T/F Radaiton induced cancer is a stochastic effect of radiation
True No threshold increase amount increases risk
36
T/F All electromagnetic radiation can cause carcinogenesis
False Not all is the same
37
Which electrons have highest bonding energy
Closer to nucleus
38
Which shell is closet to nucleus
K shell Klmnopq
39
Z number
The number of neutrons protons in a neutral atom
40
Higher atomic number (z number)
Higher the bonding energy
41
Z number is the same as # of
Electrons in a neutral atom
42
A number:
of Protons + neutrons
43
Radiation is energy in
Motion
44
Radiation moves
In a straight line from a central point It diverges
45
If the radiation beam is further away
More face face would be exposed because it is divergent
46
Radiation can be ___ or ___
Electromagnetic (waves) or particulate (particles )
47
Radiation can be _____ or ____ radiation
Ionizing | Nonionizing
48
Ionization
Reaction that has sufficient energy to remove electrons from atoms it encounters in its path
49
Wave theory
Radiation is propagated as waves Electric and magnetic fields are in planes at right angles Travel at speed low light
50
How far from source do you have to be away
6 feet
51
_____ wavelength has higher energy
Shorter
52
Frequency and wavelength are _____related
Inversely
53
Wavelengths
Distance between 2 succcesive crests or troughs Measured in meters or angstroms (X-rays)
54
Frequency
of oscillations vibrations or cycles per second
55
Electromagnetic radiation
Transfers of energy through space as a combination of electrical and magnetic fields
56
Quantum theory
Electromagnetic radiation is considered as bundles of energy called photons
57
Higher frequency _______ energy
Higher
58
Longer wavelength
Lower energy | Lower frequency
59
Ionization
Gaining or losing an electron | y
60
Ionization occurs when
Occurs when particulate or electromagnetic radiation energy is greater than binding energ
61
Threshold for ionization
10e
62
Types of ionizing good radiation
Gamma rays x rays and some UV rays
63
In ionization the ejected particle
Is a negative ion The remainder of atom is positive
64
X rays are produced when
velocity electrons are suddenly declarations when they pass close to the nuclei of high Z# absorbing material
65
3 requirements for X-ray production
Electrons High velocity of electrons High Z number absorbing material (tungsten )
66
2 mechanism of X ray production
Electron to nucleus Electron to electron interaction
67
Electron to nucleus interaction
Bermesstrahlung radiation -the fast voting electrons either slow down or stop when they come close to the nucleus of the atoms and part of their energy is transferred as X rays
68
Electron to Electron interaction
Characteristic radiation Few electrons interact with tungsten target originated electrons imparting enough energy to ionize the tungsten target When electrons displace inner shell electrons, characteristic radiation is produced
69
Electrons have different kinetic energies
True
70
Homogenous radiation
AC converted to DC All cathode electrons will have similar KE and the resulting radiation is more homogenous
71
Which is less radiation to patient homogenous or heterogenous radiation
Homogenous
72
Long wavelength radiation have more energy compared to short wavelength T/F
False
73
Which shell of an atom has the greatest binding energy
K shell
74
X rays are produced when high velocity atoms are suddenly decelerated when they pass close to the nuclei of high Z # absorbing material
False ELECTRONS not atoms
75
PID
Position indicating device | In the tube head
76
4 conditions to produce X-rays
1) Production of high speed electrons 2) Separation of electrons from tungsten filament at cathode 3) concentration of electrons: electrons are negatively charged and repel each other. We need to focus them on a small region on the anode known as the target 4) Sudden stoppage of electron stream
77
How to form electron cloud
The cathode is the source for electrons made of tungsten filament. The filament is heated at low volatile and electrons are separated from the filament -thermionic emission
78
Focusing cap
Focuses the negative electrons to the positive anode which then results in characteristic bremstahlngasads radiation
79
Anode
Tungsten target covered in copper
80
Tungsten target
High atomic number High melting point Low vapor pressure Good thermal conductivity
81
X ray tube
A glass bulb with vacuum inside it. A metal housing surrounds the tube and protects the tube from accidental damage and prevents overheating of the tube by providing a space filled with oil
82
Filtering the beam
Beam exiting the tube has different wavelengths Removes lower energy X ray photons
83
Inherent filtration
The glass covering and oil in the tube contribute to stopping low energy
84
Total filtration
Aluminum + inherent filtration
85
At 50-70 kVP
At least 1.5 mm total filtration must be used
86
Above 70 kVP
At least 2.5 mm total filtration is required X ray machines rated below 60kVp should not be used
87
Filtration reduces patient skin exposure
TRUE
88
Factors controlling X-ray beam
``` Tube voltage Exposure time Tube current Filtration Collimating Distance ```
89
KVP affects
Both quality and quantity of radiation
90
Higher kVP
1) Increase amount of radiation | 2) determine the maximum energy of x rays produced
91
An increase of 15% kVP should be accompanied by
A reduction of on half in mAs
92
An increase of 15 kVP
Would require having the exposure time Decrease of 15kVp doubling the exposure time
93
Low kVp leas to X-rays with
Longer wavelength and lower energy and so they do not penetrate much in matter
94
Higher kVp
Increases the energy of the X-ray photons which can now travel deep in tissues/matter
95
The mA or tube current of an X-ray tube affects
Quantity of the X-rays produced
96
Exposure time of an X-ray tube affects the
Quantity of X-rays produced
97
____ and ____ both control the quantity of X-rays produced
Exposure time, mA
98
MAs determine
The total number of X-ray photons produced in the beam
99
Most effective beam limiting devices
Collimating Lead
100
Collimating
To minimize the amount of radiation to patients and reduce scatter radiation
101
Collimating should restrict the beam diameter to no more than
7 cm (2.75 in)
102
The intensity of radiation varies
Inversely as the square of the source film distance
103
X-rays that pass all the way through
Dark or radioluscent
104
X rays that are absorbed completely
Radiopaque or white
105
Three means of beam attentuation
Coherent scattering Photoelectric absorption Comptons scattering
106
Scattering interaction
Photons interact with absorber atoms but then are scattered in another direction This allows us to see the different between enamel dentin bone and soft tissues
107
Coherent scattering
Low energy photons interact with outer electrons The incident photons interacts with he electron in the outer shell causing it to vibrate momentarily at the same frequency as the incoming photon
108
Photoelectric absorption
Incident photon interacts with inner e usually k Overcomes binding energy and ejects electron Ejected electron acquires the remainer KE The empty spot is usually filled
109
Photoelctron/recoil electron
Overcomes binding energy and ejects electron
110
The frequency of photoelectric interaction is inversely proportional to
Cube of photon energy Higher energy photons are less likely to undergo absorption
111
The frequency of photoelectric interaction varies directly with the third power of
The atomic number of the absorber more likely with inner shells As z number increases there is more photoelectric absorption
112
The probability that a photon will be absorbed by a photoelectric interaction in bone is approximately
6.5 times greater than in an equal thickness of soft tissue
113
Comptons scattering
Incident photon interacts with an outer electron Overcomes binding energy ejects election; ejected electron acquires part of KE Remainder of energy given off as scattered photon Major source of scatter radiation
114
Compton probability greater in
Bone than soft tissue
115
Secondary electrons give up energy by 2 processes
Collisional interaction -resulting in ionization of atom Radiatiavie interactions -Bremsstrahlung
116
% of scattering
Coherent 7% Photoelectric 27% Compton 57%
117
HVL
Half value layer Thickness of an absorber such as aluminum required to reduce by one half the number of x ray photons passing through it
118
Beam Attenuation: Monochromatic beam
A constant fraction of the beam in attenuated as the beam moves through each unit thickness of an absorber
119
The absorption of the beam depends primarily on the
Thickness and mass of the absorber and energy of beam
120
In reality beams are
Polychromatic beams not monochromatic
121
Polychromatic beams
Absorption of individual photons depends on their energy Low energy photons are much more likely to be absorbed than high energy photons
122
Beam hardening
As an X-ray beam passes through matter the intensity of the beam decreases as quantity decreases but the mean energy of the resultant beam increases
123
Collimator size
Round 2.75 Retrunagler 2 inches
124
Best collimator
Rectangular collimator
125
A digital image
Is a representation of two dimensional image as a finite set of digital values called picture elements or pixels
126
Pixel values
Typically represent gray levels colors heights opacities etc
127
Do digital save from radiation
Reduction compared with current standard of F speed film Increase in number of radiographs made Increase in the number and ease of remakes
128
Digital Imaging Chain
Image Acquistion Image processing Image Dispaly
129
Why go digital
Efficient work flow Image enhancement Better case acceptance Co-diagnosis
130
Wired systems
CCD CMOS (Phosphors uses plates)
131
Sensors are made of
Silicone
132
CMOS each pixel
Has its own transistor does not go from one well to another
133
Phosphor wireless sensor
Sensor is made from a plastic plate coated with a phosphor material sensitive to X-ray PSP sensor is exposed to X-ray The image is then digitized with a special scanner Plate must be cleared by light exposure
134
Digital Detector characteristics
Contrast resolution Spatial resolution Detector latitude Detector sensitivity
135
Contrast resolution
Ability to distinguish different desensities in the image
136
8 bit
2^8=256
137
Spatial resolution
Capacity to distinguish fine detail
138
Detector latitude
Ability of a receptor to capture a range of exposure Full range of human tissues from Gingiva to enamel
139
Detector sensitivity
Ability to respond to small amts of radiation No classification standards for dental detectors yet
140
Detector Quantum effeciency
DQE is the measure of noise and contrast expressed as a function of object detail
141
Bit depth at least
12
142
Image processing
To restor enhance or analyze -image restoration -image enhancement —brightness contrast —sharpening and smoothing —-color —Digital subtraction
143
Digital subtraction
Two radiographs are taken with identical exposure geometry over a timer interval and superimposed
144
Monitor contrast
1000:1
145
Maxillary central incisor
Receptor selection: Size 1 Sensor vertical Entire length of bite block should be used to position the sensor back in the palate
146
Mandibular anterior
Place the sensor flat on top of the tongue. Insert hero tally to the lower first molar region Root he sensor into an upright position making sure the bend in the metal bar is even with the center of the nostrils
147
Maxillary Posteriors
Retract the cheek and guide the sensor into the mouth between teeth 8 9 this is where the vault is in the palate and will give you plenty of room Push sensor back until it is level with the desired teeth
148
Mandibular Posterior
Retract place sensor into mouth between tongue and teeth at a 45 degree downward angle for comfort Slide sensor back toward themolar area centering the premolar/second molar on the center of the bite tab
149
Mandibular molar receptor
Size 2 Sensor horizontal
150
Premolar or molar Bitewing
Size 2 Horizontal or vertical
151
Overlap erro
Incorrect horizontal angulation
152
Incisal edge not visible
Incorrect sensor placement
153
Elongation error
Decreased vertical angulation
154
Foreshortening error
Increased vertical angulation
155
Cone cut error
X ray beam not centered on the receptor
156
Blooming
Each pixel cell of a ccd device converts photons to electrons during exposure Electrons oversaturate the wells
157
Auto firing
White blank images Caused by static
158
T/F photoelectric absorption is the primary contributor to the formation of a radiopgraphic image
True
159
It is recommend that na indivula operating a handheld x ray deveined wear a lead apron T/F
True
160
X ray tube length
Increasing the X-ray source to skin distance leads to a dose reduction of 10-25%
161
Reducing personal exposure
6 feet away at an angle of 90-135 Inverse square law
162
Effective dose
Occupational: 20 mSv Public: 1 mSv
163
Effective dose: lens of eye
20 mSV 15 mSv
164
Effective dose skin hands and feet
500 mSv 50 mSv
165
Which image best visualizes periodontal bone levels
Bitewing
166
The greater the object receptor distance, the less magnification there will be
False Because the beam is diverging the further away you are the larger the image will be
167
Broad radiographic examinations of the maxillofacial region
Images lack fine detail Less invasive Rapid scan time Relatively low radiation dose
168
Panoramic indications
``` Osseous components of TMJs Impacted teeth Eruption abnormalities Pathology Trauma ```
169
Focal trough
Where beam is centered (mandible)
170
Closer to the panoramic beam means the image projects
Higher due to slight tilt
171
Ghost images
Always on opposite side and blurry
172
Head rotation
Whatever side the patient head is turned toward is more magnified The focal trough goes to the left
173
If too far forward
Anteriors blurred
174
Too far back
Too much mandible
175
Overexposed
KVP to high black image
176
Underexposed
KVP too low brigh white
177
Lateral cephalmoteric skull projection
Evaluations of craniofacial skeletal morphology developmental growth occlusal relationships and treatment progress
178
PA cephalometric
Evaluation of facial asymmetry and orthographic surgery
179
Tongue not on palate
Radiolucent cant see
180
Too forward
Blurring of anterior teeth A lot more spine
181
To far back
Anterior look too large No spine Huge mandible
182
Chin tilted down
Exaggerated smile line Mandibular anterior teeth look too small
183
Chin elevated
Flat smile line

Oral Radiology (1 decks)

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