Exam 1 (1-4) Flashcards
(171 cards)
1
Q
Dental radiographs:
A
Images or pictures produced by x-rays
Remain the basis for many diagnostic procedures
Play an essential role in oral health care
2
Q
What is Radiography?
A
Making of radiographs by exposing an image receptor,
either film or digital sensor
3
Q
Dental radiography
A
The purpose is to provide oral health care team radiographs of the best possible diagnostic quality.
The goal is to obtain the highest quality radiographs while maintaining the lowest possible radiation exposure risk for the patient.
4
Q
Oral radiology:
A
Study of x-rays and techniques used to produce radiographic images
X-Ray discovered by Professor Wilhelm Conrad Roentgen 1895
5
Q
X-ray:
A
Initially, X represented the unknown.
6
Q
Radiograph:
A
Photo negative and x-ray film are similar.
X-rays resemble radio waves.
Prefix “radio” and suffix “graph” combined.
7
Q
Panoramic radiography
A
Capable of exposing the entire dentition and surrounding structures on a single image
8
Q
Computed tomography scan (CT)
A
Imaging a single selected plane of tissues
Delivers high dosage of radiation
9
Q
Cone-beam computed tomography (CBCT)
A
Lower doses of radiation
* Purported to become the gold standard
10
Q
Early dental x-ray film packets
A
Glass photographic plates wrapped in black paper and rubber
11
Q
Machine-wrapped dental x-ray film packet
A
First available in 1919 from Kodak
12
Q
Emulsion coating:
A
One-sided coating
Required long exposure times
Both sides coated now
Exposure times much shorter
13
Q
Who introduced digital radiography and what does it do?
A
Digital imaging systems replace film as the image receptor with a sensor.
French dentist- Frances Mouyen, 1987
RadioVisioGraphy
14
Q
What are the advantages of digital radiography?
A
Advantages:
Reduction in radiation dosage
Elimination in film and processing chemistry
Elimination of film packaging disposal
15
Q
Bisecting technique:
A
First and earliest method
A. Cieszyński, 1907
Applied the rule of isometry to dental radiology
16
Q
Paralleling technique:
A
Franklin McCormack, 1920
Less-complicated; more practical
17
Q
Uses of Dental Radiographs:
A
Detect, confirm, and classify oral diseases and lesions
Detect and evaluate trauma
Evaluate growth and development
Detect missing and supernumerary (extra) teeth
Document the oral condition of a patient
Educate patients about their oral health
18
Q
Matter:
A
Anything that occupies space and has mass.
19
Q
Energy:
A
The ability to do work and overcome resistance
Examples:
Heat
Light
Electricity
X-radiation
20
Q
Atom:
A
The smallest particle of an element that still retains the properties of the element
21
Q
Molecule:
A
The smallest particle of a substance that retains the properties of that substance
Atoms + Atoms = molecule
22
Q
Atoms are composed of:
A
Electrons (-)
Negative charge
Protons (+)
Positive charge
Neutrons (neutral)
No charge
23
Q
Atoms:
Electrons revolve around a nucleus in paths called shells or energy levels.
Protons and neutrons form the nucleus (center)
A
In the neutral atom, the number of positively charged protons in the nucleus is equal to the number of negatively charged orbiting electrons. The innermost orbit or energy level is the K shell, the next is the L shell, and so on.
24
Q
Binding energy:
A
Electrons are maintained in orbits by positive attraction of protons.
25
Ion:
is an **atom** with **extra (+)** or **missing (-)** electrons
## Footnote
**Charged particle**
26
Positive ion:
**Atom** from which an **electron (-)** has been **removed**
## Footnote
**(more protons than electrons)**
27
Negative ion:
**Negatively** charged electron (-) **separated** from the **atom**
**(-e itself)**
28
Ion pair:
**Positively charged** atom ion and **negatively charged** electron ion
29
Ionization:
Formation of ion pairs
30
What's going on in this picture?
Ionization is the formation of ion pairs. When an atom is struck by an x-ray, an **electron may be dislodged and an ion pair results.**
31
Radiation:
**Emission and movement of energy through space**
Electromagnetic radiation (x and gamma rays)
Particulate radiation (alpha and beta particles)
32
Ionizing radiation:
Any radiation that produces ions
33
Radioactivity:
The process whereby certain **unstable elements** undergo spontaneous disintegration **(decay) i**n an effort to **attain a stable nuclear state.**
## Footnote
**Dental x-rays do not involve the use of radioactivity.**
34
Electromagnetic Radiation:
Movement of **wave-like energy** through space as a combination of electric and magnetic fields.
35
Electromagnetic spectrum:
Consists of an **orderly arrangement** of all known **radiant energies.**
36
X-radiation includes:
Gamma rays
Ultraviolet rays
Visible light
Infrared
Microwave
Radio waves
37
All energies of the electromagnetic spectrum share the following properties:
Travel at the speed of light
**Have no electrical charge**
**Have no mass or weight**
**Pass through space** as particles and in a **wave-like motion**
Give off an electrical field at **right angles** to their path of travel and a magnetic field at right angles to the electric field
**Have energies that are measurable and different**
38
Electromagnetic radiation display two contradictory properties:
Believed to move through space as both a **particle** and a **wave**.
39
Particle or quantum theory:
Assumes **electromagnetic radiations** are particles, or quanta called **photons**
## Footnote
**Photons are bundles of energy that travel through space at the speed of light**
40
Wave theory:
Assumes electromagnetic radiation is propagated (spread) in the form of waves:
Wavelength
Frequency
Velocity
41
Wavelength:
Distance between two similar points on two successive waves
May be measured in the metric system or in **angstrom (Å)** units
**Wavelength is determined by distances between crests.**
42
Frequency:
The measure of the **number of waves** that pass a given point per unit of time
**Hertz (Hz)**
Special unit of frequency
**One hertz equals one cycle per second.**
43
Velocity:
**Speed** of the wave
44
Soft radiation:
Grenz rays
**Limited penetrating power**
Unsuitable for exposing dental radiographs
(**long wavelength**)
45
Hard radiation:
Wavelengths used in diagnostic dental radiography range from about
**0.1 to 0.5 Å**
Great penetrating power
(**Short wavelengths**)
46
Properties of X-rays
X-rays are believed to consist of minute bundles (or quanta) of **pure electromagnetic energy called photons.**
47
Photons:
Photons have **no mass or weight, are invisible,** and cannot be sensed.
**X-ray photons** are often referred to as “**bullets of energy**.”
48
X-rays:
Are invisible
**Travel in straight lines**
Travel at speed of light
Have no mass or weight
**Have no charge**
49
X-ray photons have the ability to penetrate
materials or tissues depends on:
The **wavelength** of the x-ray
and
**thickness and density of the object.**
50
Materials that are extremely dense and have a high atomic weight will absorb more x-rays than thin materials with low atomic numbers.
**Dense** materials such as bones appear **radiopaque** (white/light gray) **(bones/teeth = white/gray)**
**Less dense** materials such as the **pulp chamber** appear **radiolucent** (black/dark gray) **(spaces/foramen = black)**
51
In a dental x-ray tube, the **kinetic energy** of electrons is **converted** to **electromagnetic energy** by the formation of:
**General or bremsstrahlung radiation**
German for “braking”
Characteristic radiation
52
General/bremsstrahlung radiation:
Produced when **high-speed electrons** are **stopped or slowed** down by the **tungsten** atoms of the dental x-ray tube.
53
Characteristic radiation:
**(C)**
Produced when a **high-speed electron** from the tube filament **collides** with an **orbiting K-shell** electron of the tungsten target.
54
Primary radiation:
General and/or characteristic radiation generated at a **target** inside x-ray tube head
Refers to the **useful beam**, or those x-rays generated for the
**purpose of making a radiographic image**
55
Secondary radiation:
Formed as a result of primary radiation striking and interacting with matter
Not as penetrating as primary radiation
**Not useful in the production of a radiographic image**
**Can contribute to a lowered contrast, poor quality image**
56
Scatter radiation:
Form of secondary radiation
Results when x-rays are **deflected in all directions** as a result of interaction with matter
Not useful
**Can cause unnecessary additional exposure to patient tissues and to the careless operator** who does not follow safety protocols
**Lead apron + lead wall = no scatter radiation**
57
Absorption:
Process of **transferring energy of x-rays to atoms** of material through which the x-ray beam passes
The beam of x-rays passing through matter is
**weakened and gradually disappears.**
(**tooth absorbs energy = turns white**)
58
Interaction of X-rays with Matter:
**Four possibilities:**
1. No interaction
2. Coherent scattering
3. Photoelectric effect
4. Compton effect
59
No interaction:
## Footnote
**(A)**
X-ray photon can pass through an atom **unchanged and no interaction** occurs.
In dental radiography, about 9% of the x-rays pass through the patient’s tissues without interaction.
60
Coherent scattering:
**(B)**
Incoming x-ray photon interacts with the electron by causing the **electron to vibrate at the same frequency as the incoming x-ray photon.**
Accounts for about 8% of the interactions of matter with the dental x-ray beam
61
Photoelectric effect:
Incoming x-ray photon **collides with an orbital electron** and imparts **electromagnetic energy** to the electron in the form of **kinetic energy** causing **electron to fly from its orbit, creating an ion pair.**
**All-or-nothing energy loss**
High-speed electron (called a **photoelectron**)
**knocks other electrons from the orbits of other atoms** (forming secondary ion pairs) until all its energy is used up.
Accounts for about **30%** of the interactions of matter with the dental x-ray beam
62
Compton scattering:
Similar to the photoelectric effect
Incoming x-ray photon **collides** with an orbital electron and **ejects it**. But, only a **part of the x-ray energy is transferred** to the electron, and a new, **weaker x-ray photon** is formed and **scattered** in a **new direction**.
Accounts for about **60%** of the interactions of matter with the dental x-ray beam.
63
The International Commission on Radiation Units and Measurements
## Footnote
**(ICRU)**
has established standards that clearly define **radiation units** and **radiation quantities**. The most widely accepted terms used for radiation units of measurement come from the **Système Internationale (SI)**, a modern version of the metric system.
The SI units are:
Coulombs per kilogram (**C/kg**)
Gray (**Gy**)
Sievert (**Sv**)
64
Radiation Measurement Terminology:
**Quantity SI Unit**
Exposure coulombs per kilogram (C/kg)
Absorbed dose gray (Gy)
Dose equivalent Sievert (Sv)
Effective dose equivalent microsievert (µSv)
65
Exposure:
**Measurement of ionization in air produced by** **x- or gamma rays**
Unit for measuring exposure is coulombs per kilogram **(C/kg)**
**Does not** measure the **radiation absorbed by body tissues** or other materials.
**Exposure does not** become a **dose** until the radiation is **absorbed.**
66
Absorbed dose:
**Amount of energy deposited in any form of matter**, such as the tissues of the head and neck of a patient, **by any type of radiation (alpha or beta particles, x- or gamma rays)**
Unit for measuring absorbed dose is the gray **(Gy)**
67
Dose equivalent:
**Used to compare the biological effects of the various types of radiations**
Product of the absorbed dose times a biological-effect qualifying or weighting factor determined by quantum physicists
Unit for measuring dose equivalent is the **sievert (Sv)**
weighing factor for X-ray = 1
**absorbed dose and dose equivalent are equal**
68
Effective dose equivalent:
**Used to compare the risk of radiation exposure producing a biological response**
Expressed using the term microsievert **(μSv)**
Compensates for the differences in area exposed and tissues, **critical or less critical**, that may be in the path of the x-ray beam
69
Background radiation:
**The ionizing radiation that is always present in our environment**
Dental x-rays and other man-made medical applications account for **48%** of total radiation exposure to U.S. population.
70
Who is responsible for the radiation dose the patient occurs at the time of exposure?
the radiographer
71
Which part of the dental x-ray machine contains the master switch and other exposure buttons?
the control panel
72
What enables the tube head to be positioned?
the extension arm or bracket
73
Which part of the dental x-ray machine contains the x-ray tube from which x-rays are generated?
the tube head
74
What do dental x-ray machines require in order to produce x-rays?
an electrical source.
75
What are the different options available for control panel placement?
1. It may be integrated with the extension arm
2. It may be remote from the unit or mounted on a shelf or the wall.
76
What are the five major controls that will be present on dental x-ray machines?
1. the line switch to an electrical outlet
2. the milliampere (**mA**) selector
3. the kilovolt peak (**kVp**) selector
4. the timer
5. the exposure button
77
This switch, located on the control panel, maybe flicked ON or OFF. It features an indicator light that turns on indicating when the machine is operational.
What is it called? Do this first!
Line Switch
78
What measures the **amount of current** passing through the wires of the circuit?
The milliampere selector; **mA**
## Footnote
**determines #free electrodes at cathode (-) → # X-rays produced**
79
How is the mA set?
it is set by turning a selector knob or by pressing the marked push button of touching a keypad.
80
What enables the operator to change the peak kilovoltage?
a kilovolt peak (kV**p**) selector
**(penetrating)**
**kVp** determines the **speed** of electrons traveling toward the **target** on the **anode (+)** and, therefore, the penetrating ability of the x-rays produced.
81
What determines the **speed of electrons traveling toward the target** on the anode and, therefore, is the penetrating ability of the x-ray produced?
kV**p (penetrating)**
82
What sets the timer?
What is the purpose of the timer?
How many impulses are there in a second?
- the selector knob, button or keypad
- it serves to regulate the **duration of the interval** that the current will pass through the x-ray tube.
**60/sec**
83
What is the "dead man" exposure switch?
it is an exposure switch that **automatically terminates** the exposure when the operator's **finger ceases to press on the timer button.**
84
X-ray machines with **digital electronic timers** are accurate to the ______ of a second?
1/100-second intervals
85
How far should the area of protection be from the source of the x-ray beam?
Why is it important to firmly press the timer button for the **full duration** of an exposure?
6 feet
letting go of the results in the formation of an **insufficient number of x-rays** to properly expose the image receptor. There is a **beep that sounds** when this is done. **The beep is required by law.**
86
Why is the extension arm hollow?
to permit the **passage of electrical wires from the control panel to the tube head** from one or both sides at a point where the **tube head attaches to a yoke.**
87
The tube head is attached to the extension arm by means of a _____ that can revolve **360 degrees horizontally** where it is connected?
Yoke
88
What does the tube head's heavy metal, lead-lined housing contain?
x-ray dental tube
insulating oil
step-up and step-down transformers
89
What functions are performed by the tube head metal housing?
1. it protects the x-ray tube from accidental damage.
2. it increases the safety of the x-ray machine by grounding its high voltage components to prevent electrical shock.
3. it prevents overheating of the x-ray tube by providing a space filled with oil, gas, or air to absorb the heat created during the production of x-rays.
4. it is lined with lead to absorb any x-rays produced that do not contribute to the primary beam that exits through the port in the direction of the position indicating device (PID)
90
Identify #1
Tube head
91
Identify #2
Low voltage transformer
92
Identify #3
Primary beam
93
Identify #4
High voltage transformer
94
Identify #5
Window
95
Identify #6
Collimator
96
Identify #7
Central ray
97
Identify #8
Filter
98
Identify #9
PID
99
Identify # 10
X-Rays
100
Identify # 11
Port
101
Identify # 12
Oil
102
Identify #13
Copper stem
103
Identify # 14
Cathode (-)
104
Identify # 15
Focusing cup
105
Identify # 16
Anode (+)
106
Identify # 17
Electron cloud
107
Identify # 18
Filament
108
Identify # 19
Glass envelope
109
Identify # 20
Radiator
110
Identify # 21
Tungsten target
111
Identify # 22
Vacuum
112
How can electricity be defined?
it can be defined as **electrons in motion.**
113
Two electrical circuits are used in producing dental x-rays, what are they?
1. a filament circuit
2. a high voltage circuit
114
What does the filament circuit do?
it provides a low voltage (**3-8 V**) to the filament of the x-ray tube to generate a **source of electrons** needed for the production of x-rays
115
What does a high-voltage circuit provide?
it provides the high voltage (**50-100 kV**) necessary to accelerate the electrons from the **cathode** **filament** to the **anode target.**
116
What is required to decrease (**step down**) or increase (**step-up**) ordinary
110-V or 220-V current that enters the x-ray machine.
a transformer
117
What is the purpose of a step-down transformer?
it **decreases the voltage** from the wall outlet to approximately **5V,** just enough to **heat the filament and form an electron cloud.**
118
What is the purpose of a step-up transformer?
it **increases the voltage** from the wall outlet to approximately **50-100 kV** to propel the electrons toward the target.
119
What measures the **number of electrons** that move through conductor?
the amperage
120
What is the **unit of quantity** of electric current?
ampere
121
What does an increase in amperage result in?
it results in an **increase in the number of electrons available to travel** from the **cathode to the anode** when the tube is activated; thus producing more x-rays.
122
True or False
A small current is required to generate the number of electrons necessary to produce dental x-rays.
True
123
What does the term **milliampere (mA)** denote?
it denotes that **1/1,000** ampere is used.
124
What mA is typically used in dental x-ray machines?
**4-15 mA**
125
# Define voltage?
it is the **electrical pressure between two electrical charges**. It determines the **speed** of the **electrons** traveling from **cathode to anode**.
126
What happens when voltage is increased?
## Footnote
.
the electrons **travel faster** and produce a **harder type of radiation**
127
What is a **polychromatic** beam?
**X-rays of different energies**; containing **high-energy rays** and also **containing soft rays** that have barely enough energy to escape from the tube.
128
What is the kV range that dental x-ray machines can operate within?
**50 kV- 100 kV**
129
What types of current may be used by dental x-ray machines?
alternating current (**AC**) or direct current (**DC**)
130
What is alternating current (AC)?
A flow of electric charge that **alternates between positive and negative phases**. There are **60 direction changes per second.** X-rays are only produced when the current is in the **positive direction** (up).
131
What does alternating current causes the dental x-ray machine to produce?
it causes it to produce x-rays in a **series of bursts, or pulses**, rather than in a **continuous flow**
132
What is direct current (DC)?
**this current flows continuously in one direction**, eliminating the alternating cycles; resulting in a more **constant and even flow** of x-rays.
This is similar to the current produced by battery power.
133
What causes a dental x-ray machine to produce x-rays at a **more consistent wavelength**?
Direct current flow
134
What is a key difference between AC and DC x-ray machines?
Direct current dental x-ray machines produce more consistent exposures at very short exposure times and may **slightly reduce patient radiation exposure**.
135
When are x-rays produced?
they are produced when a stream of **high-speed electrons** is **stopped** or **slowed down** and diverted off course.
136
What three conditions must exist for x-rays to be produced?
1. An available source of **free electrons.**
2. **High voltage** to impart speed to the electrons (**kVp**)
3. A **target** that is capable of **stopping/slowing** the electrons.
137
What is located inside the tube head, is a glass bulb from which the air has been pumped to create a vacuum?
the x-ray tube
138
# Define cathode:
a negative (-) electrode
139
# Define anode:
a positive electrode
140
What is the purpose of the cathode?
To **supply the electrons** necessary to produce x-rays. It contains the tungsten **filament wire**
141
Explain the process of **thermionic emission.**
The tungsten **filament wire**, when **heated to incandescence**, produces **electrons**.
142
True or False
The cathode consists of a thin spiral filament of tungsten wire.
True
143
What is the benefit of Tungsten?
Its **high atomic number** makes it possible to **liberate electrons**, through **thermionic emission**, from their orbital shells when the **metal is heated**. These **released electrons** then form an **electron cloud** around the **wire**.
144
What is the purpose of the focusing cup?
it **directs (focuses)** the electrons toward the **target** on the **anode**.
145
What accurately controls the **thermionic emission** and therefore controls the **quantity** of **free electrons available**?
**mA**
146
What is the purpose of the anode?
the purpose is to provide a **target that stops** or significantly **slows** the **high-velocity electrons, converting their kinetic energy into x-rays** (electromagnetic energy).
147
What does the anode consist of?
a copper bar with a tungsten plate imbedded in the end that faces the focusing cup of the cathode
148
What is set into the copper at an angle of 20 degrees to the cathode?
the tungsten plate (called the target)
149
What does the **20-degree angle** of the **target** (tungsten plate) direct?
it directs most of the x-rays produced in **one direction** to become the **primary beam**.
150
What is the focal spot?
it is a small rectangular area on the **target of the anode** to which the **focusing cup directs the electron beam**.
151
Why is the focal spot size important?
it plays an important role in determining the radiographic image **sharpness**
152
Why is the tungsten plate embedded in the core of a copper bar?
because **copper is highly conductive** and **carries the heat** generated off to the **radiator** which is just **outside the tube**.
153
If the tube head is **properly sealed**, ____ is the only place through which **x-rays can escape.**
the port
154
Why is the **collimator** useful?
it is useful because it further **reduces (funnels)** the x-ray beam to the desired size after it **exits through the port.**
155
How do x-rays travel?
in diverging **straight lines** as they radiate from the focal spot. **This beam** of **x-rays** is called a useful beam or **primary beam**.
156
What is a filter?
it is a **thin sheet** of aluminum **placed in the path** of the x-ray beam.
157
What does the **intensity** of the x-ray beam refer to?
it refers to the **quantity** and **quality** of the x-rays.
158
# Define **quantity.**
this is **the number** of **x-rays** in the **beam = (mA)**
159
# Define **quality.**
this refers to the **energy strength** or **penetrating** ability of the **x-ray beam**. (**kVp**)
160
# Define intensity
the product of the **number of x-rays** and the **energy strength** of the x-rays per unit of area per unit of time. The **intensity** of the x-ray beam is affected by **milliamperage, kilovoltage, exposure time, and distance**.
161
What happens if you **increase the mA**?
there will be an **increase** in the **number of electrons.**
162
What is the ethical responsibility of the radiographer?
to produce the highest diagnostic-quality radiographs for patient who have **given consent.**
163
What are the three basic requirements for an acceptable diagnostic radiograph?
1. All parts of the structures recorded must be imaged as **close to their natural shapes and sizes** as a patient's oral anatomy will permit.
2. The area examined must be imaged completely with enough surrounding tissue to **distinguish between the structures**.
3. The radiograph should be **free of errors** and **show proper density, contrast, and definition**
164
Define radiolucent.
It is the portion of the image that is **dark or black**.
Structures that appear **radiolucent** permit the passage of x-rays with **little or no resistance.**
***transparent to X-rays***
Ex: **pulp chamber, PDL**
165
Define radiopaque.
The portion of the image that is **light or white**. The structures that appear this way are **dense and absorb** or resist the passage of x-rays.
*Not transparent*
Ex: **enamel, dentin and bone**
166
# Define density.
The **degree of darkness or image blackening**.
An image that appears light is said to have little density; whereas an image that **appears dark** is said to have **more density**.
167
\_\_\_\_\_\_ is increased when the **milliamperage** (**mA)** of the exposure time is **increased** and more x-rays are produced to reach the film emulsion or digital sensor.
The degree of darkening of a radiograph
**Increased mA = dark X-rays**
168
# Define contrast.
**many shades of gray that separate the dark and light areas**.
An area with good contrast will contain **black, white, and enough shades of gray** to **differentiate between structures and their conditions**.
169
What type of contrast describes a radiograph in which the density differences between adjacent areas are small?
Low contrast or Long Scale
## Footnote
**Hard to distinguish between colors**
**Higher kVp = low contrast**
170
# Define sharpness
It is a geometric factor that refers to the **detail and clarity** of the **outline** of the **structures** shown on a radiograph
171
What generally causes unsharpness?
**movement** of the patient, image receptor, or the tube head **during the exposure.**
