Chapter One Radiation History ,chapter two radiation physics, chapter 3 radiation characteristics. Flashcards
0
Q
Radiograph
A
A two dimensional representation of a three dimensional object. In practice, often called an X-ray This is not correct.
1
Q
Radiation
A
A form of energy carried by waves or a stream of particles
2
Q
Uses of dental radiographs
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Detect lesions, confirm or classify suspected des ease, localize lesions or foreign object, provide information during dental procedures such as root canal therapy, placement of dental implants, illustrate changes secondary to caries, periodontal disease, and trauma, document the condition of a patient at a specific point in time, aid in development of a clinical treatment plan.
3
Q
The history of dental radiography begins with the?
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Discovery of x ray.
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Who discovered the X-ray and when.
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Wilhelmina Conrad roentgen , on November 8 1895
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Q
Who is credited with the first practical use of radiographs in dentistry? What year?
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C. Edmund Kells 1896. He exposed the first radiograph in the United States using a living person.
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Q
Other pioneers in dental radiography?
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William H Rollins , a Boston dentist who developed the first dental x ray unit.
7
Q
The meaning of the term quality in dental radiography is used to
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Discernible the mean energy or penetrating ability of the x ray beam.
8
Q
Voltage is
A
A measurement of force that refers to the potential differences between two electrical charges.
9
Q
Inside the dental X-ray tube head voltage is
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The measurement of electrical force that causes electrons to move from the negative cathode to the positive anode.
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Q
Voltage determines
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The speed of electrons that travel from cathode to anode.
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Q
When voltage is increased
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The speed of electrons is increased.
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Q
1 kilovolt (kv) is equal to
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1000 volts
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Q
Kilovoltage peak ( kvp )
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Maximum or peak voltage
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Q
Increasing the kilovoltage peak results in
A
A higher energy X-ray beam with increased penetrating ability
15
Q
Density
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The overal blackness of an image.
16
Q
An adjustment in kilovoltage peak results in.
A
Change in the density of the dental radiograph
17
Q
When the kilovoltage peak is increased while other exsposire factors remain constant.
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The result exhibits increased density and appears darker.
18
Q
When low kilovoltage peak settings are used (65- 70)
A
A high contrast image will result.
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Q
A high contrast image
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Lots of light lots of dark few gray
20
Q
A image with high contrast is useful for detection and progression of dental carries.
A
True
21
Q
Exposure time
A
Refers to the interval of time during which X-rays are produced.
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Q
Exposure time is measured in
A
Impulses
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Q
X-rays are created in a series of
A
Burst or pulses rather than a continuous stream.
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One impulse occurs every
1/60 of a second ( 60 impulses a second)
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Amperage determines
The amount of electrons passing through the cathode filament.
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An increase in the number of electrons available to travel from the cathode to the anode results in?
Production of an increases number of X-rays
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The quantity of the X-rays produced is controlled by
Milliamperage
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Both milliamperes and exsposure time have a
Direct influence on the number of electrons produced by the cathode filament.
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The product of milliamperes and exposure time is
Determined milliampere-seconds ( mAs)
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Milliampere x exposure time (seconds) =
Milliampere-seconds
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Intensity
The product of quantity(number of X-ray photons) and quality(energy of each photon) per unit of area per unit of time of exsposure.
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Intensity of yhe X-ray beam is effected by a number of things such as
Kilovoltage peak, milliamperage, exsposure time and distance.
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The inverse square law is used to
Explain how distance effects the intensity of the X-ray beam
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The inverse square law
The intensity of radiation is universally proportional to the square of the distance from the source of radiation
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As one variable increases the other is decreased this is called
Inversely proportional
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Aluminum filters are placed in the path of the beam inside the dental X-ray tub head to ?
Reduce the intensity of the X-ray beam
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Aluminum filters are used to remove
The lowenergy ,less penetrating , longer- wavelength X-rays.
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Aluminum filters increase the
Mean penetrating capability of the X-ray beam while reducing the intensity.
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Matter
Anything that occupies space and hasmass
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When matter is altered
Energy results
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The fundamental unit of matter is
The atom
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Nucleus
Dense core of the atom
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Nucleus is composed of
Protons and neutrons
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Protons and neutrons are also known as
Nucleons
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The number of protons inside the nucleus
Equals the number of electrons outside the nucleus and determines the atomic number of the atom.
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Each atom has an
Atomic number
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Hydrogen the simplistic atom has the atomic number of
1
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Electrons
Are tiny negatively charged particles that have very little mass
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Electrons Tavel around the nucleuse in path mown as
Orbits or shells
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Shells are designed with the letters
K-Q, k being the closest to the nucleus and having the highest energy level.
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Electrons are maintained in there orbits by
Electrostatic force
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Electrostatic force
Attraction between the positive nucleus and negative electrons. This is known as BINDING ENERGY.
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The binding energy is determined by
The distance between the nucleus and the orbiting electron and is different for each shell.
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The strongest binding energy is found
Closest to the nucleus in the k shell.
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If the atom has more electrons than protons and neutrons it has a
Negative charge.
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The atom that loses an electron and has more protons and neutrons has a
Positive charge
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Radioactivity
The process by which certain unstable atoms or elements undergo spontaneous disintegration, or decay , in an effort to attain more balanced nuclear state.
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Particulate radiations
Are tiny particles of matter that posses mass and travel in straight lines at high speeds.
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Particulate radiations transmit kinetic energy by means of
There extremely fast-moving masses.
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Electrons can be classified as
Beta particles or cathode rays
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Cathode rays are
Streams of high-speed electrons that originate in an x-ray tube.
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Electromagnet radiation
Propagation of wavelike energy ( without mass) through space or matter.
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Electromagnet radiations are man made or occurs naturally such as
Cosmic rays, gamma rays, X-rays, ultraviolet rays, visible light, infrared light, radar waves,microwaves, radio waves.
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Velocity
The speed of the wave.
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Wavelength
The distance between the crest of one wave and the crest of the next. And determines the energy and penetrating power of the radiation.
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The shorter the distance between the crest ,
The shorter the wavelength.
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The shorter the wavelength
The higher the energy and ability to penetrate matter.
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Frequency
The number of wavelengths that pass a givin point in a certain amount of time.
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If the frequency of the wave is high
The wavelength will be short.
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If the frequency of the wavelength is low
The wavelength will be long.
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X rays used in dentistry have a wavelength of
0.1 nm or 0.00000000001 m
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Control panel
Contains an on off switch and indicator light.
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Extension arm
Suspends the X-ray tube head and houses the electricle wires. Allowed for movement and possitioning of the tube head.
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Tube head
Tightly sealed heavy metal housing that contains the X-ray tube that produces dental X-rays.
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Insulating oil
Surrounds the X-ray tube and transformers inside the tub head. Prevents over heating.
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Lead collimator
Lead plate with central hoe that cites directly over the opening of the metal housing. Restricts the size of the X-ray beam
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Position indicating device. Pid
Aims and shapes the X-ray beam
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Anode
Positive electrode used to convert electrons into X-ray photons.
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Amperage
Measurement of the number of electrons moving through a conductor.
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Current is measured in
Amperes (A) or milliamperes (mA)
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Voltage is the measurement of
Electr icle force that causes electrons to move from a negative pole to a positive one.
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Voltage is measured in
Volts (v) or kilovolts kV
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A step up transformer is used to
Increase the voltage from the incoming 110- or -220 line voltage to thec65,000 to 100'000 volts used by the high voltage circutes.
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A step up trans former has more
Wire coils in the secondary coil than the primary coil.
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The electrons travel from the cathode to the
Anode
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When electrons strike the tungsten target, their energy of motion ( kinetic energy) is converted to
X ray energy nd heat
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Less than 1% is of the energy is converted to X-rays the remaining 99% is
Lost as heat.
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Scatter radiation is
Detrimental to both the patient and the radiographer
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All ionizing radiations are harmful and produce biological changes in living tissue
True
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Although the amount o xradiation in dental radiography is
Biological damage does occurs.
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The two specific mechanisms of radiation injury that are possible.
Ionization , free radical formation.
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When x rays strike patient tissue
Ionization results
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X radiation causes cell damage primarily through the formation
Of free radicals.
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Free radical formation occurs when
An x ray photon ionizes water,the primary component of living cells.
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Ionization of water results in
The production of hydrogen and hydroxyl free radicals.
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A free radical is
An un charged ( neutral ) atom or molecule that exist with a single, un paired electron in its outer most shell. IT IS HIGHLY REATIVE AND UNSTABLE
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The life time of a free radical is
10 -10 seconds
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To achieve stability a free radical may
1 recombine with out causing changes in the molecule 2 combine with other free radicals and cause changes 3 combine with ordinary molicules to form a toxin
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Damage to living tissues caused by exspoure to ionizing radiation may result from
A direct hit and absorption of an X-ray photon within a cell or from the absorption of an x ray photon by the water within a cell accompanied by free radical formation.
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Two theories are used to discribe how radiation damages biological tissue:
The direct theory and the indirect theory.
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Direct theory of radiation injury
Suggest that cell damage results when ionizing radiation directly hits critical areas, or targets, within the cell.
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Indirect theory of radiation in jury
Suggest that x ray photons are absorbed within the cell and cause the formation of toxins, which, in turn , damage the cell.
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Dose-response curve
Used to correlate the response or damage, of tissues with the dose or amount of radiation received.
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When a dose and damage are plotted on a graph
A linear, nonthreshold relationship is seen.
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Stochastic effects
Occur as a direct function of dose.
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Non stochastic effects
Are somatic effects that have a threshold and that increase in severity with increasing absorbed dose.
107
Non stochastic effects include
Erythema, loss of hair, cataract formation, and decreased fertility.
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The more radiation received and the faster the dose rate
The shorter the latent period
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A period of injury occurs
After the latent period. A variety of cellular injuries may result such as... Cell death, changes in cell function, breaking or clumping of chromosomes , formation of giant cells , cessation of mitotic activity, and abnormal mitotic activity.
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Total dose
Quantity of radiation received, or total amount of radiation energy absorbed.
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Cell sensitivity
More damage accrues in cells that are most sensitive to radiation, such as rapidly de voiding cells and young cells.
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Age
Children are more susceptible to radiation damage than adults.
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Sort term effects
Effects that are seen within minutes days or weeks. Associated with large amounts of radiation absorbed in a short amount of time..
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Acute radiation syndrome ARS
Short term includes nausea vomiting dire a hair loss and hemorrhage
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Somatic Effects
Are seen in the person who has been irradiated. changes are not transmitted to future generations.
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Cells that are radio sensitive include
Blood cells immature reproductive cells, and young bone cells.
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The cell that is most sensitive to radiation is.
Lymphocyte
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Radio resistant cells include.
Bone,muscle,and nerve,
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Dose
Can be defined as the amount of energy absorbed by a tissue
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Radiation absorbed dose RAD
Traditional unit of dose
121
1 gy=
100 Rads
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Background radiation
A form of ionizing radiation ubiquitous in the environment. Naturally accruing includes cosmic radiation and terrestrial radiation.
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Examples of terrestrial radiation
Potassium -40 and uranium
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In the us the average dose of background radiation received by an individual ranges from
150 to 300 mrads per year
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Film speed
F is fastest
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Collimation
Radiation exsposure can be limited by using rectangular collimating.
127
Rectangular collimating reduces the absorbed dose by
60 to 70%
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Technique radiation exsposure can be limited by
Increasing the source to film distance., use of long cone paralleling technique
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Exsposure factors radiation exsposure can be limited by
Using a higher kilovolt age peak.
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Added filtration
Referes to the placement of aluminume discs in the path of the x ray beam. Between the collimator and the tube head seal
131
Filtration of the X-ray beam results in
Higher energy and more penetrating useful beam
132
Total filtration ( inherent plus added)
Regulated by state and federal laws. Machines operating at or below 70 KVM require a minimum total of 1.5 mm aluminume filteration
133
Machines operating above 70 KVM require a minimums of
2.5 mm aluminum filteration
134
Pid position indicating device
(cone) used to direct the X-ray beam
135
Of the three types of pid the most effective in reducing patient exposure
Rectangular
136
Adequate distance to maintain from the primary beam is
6 feet
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The most recent report in 2003 for MPD in occupational exposed person is
5.0 rems per year o.o5 sv year
138
Mad maximum accumulated dose
Over a life time and based on the persons age.
139
Alara
As low as reasonable possible.
