Final Exam Flashcards
What is radiolucent?
The portion of a processed image that is dark or black
What is an example of someone that appears radiolucent? Why?
caries appear radiolucent, caries are less dense than surrounding structures
How does radiopaque appear?
It is the portion of a processed image that appears light or white
What is an example of something that appears radiopaque? Why?
metallic restorations appear radiopaque: Because they are very dense and absorb radiation
What are the two types of bones in the human body?
cortical or cancellous
What is another term for cortical bone?
compact bone
What is cortical bone?
the dense outer layer of bone
How does cortical bone appear on x-ray
radiopaque
What is a cancellous bone?
Soft spongy bone between two layers of dense cortical bone
What is a cancellous bone composed of?
Numerous bony trabeculae ( lattice shaped spaces filled with bone marrow)
Is cancellous bone radiopaque or radiolucent?
Mostly radiolucent
What is trabeculae?
Denser boney pieces, that are radiopaque
Is bone marrow Radiolucent or radiopaque?
Radiolucent
Is the inferior border of the mandible composed of cortical or cancellous bone?
cortical
What is this a picture of?
Cortical (Compact Bone)
What is this a picture of?
Cancellous bone
What is this a picture of?
Trabeculae (cancellous bone)
What is this a picture of and what is it? What is an Example?
Process- Obvious prominence or projection of bone
ex. coronoid process of mandible
What is this a picture of and what is it? What is an example?
Ridge- Linear prominence or projection
Ex. External oblique ridge
What is this a picture of and what is it? What is an example?
Spine- Sharp, thorn-like projection
ex. anterior nasal spine of maxilla
What is this a picture of and what is it? What is an example?
Tuberosity- Rounded prominence of bone
ex. maxillary tuberosity
What is this a picture of and what is it? What is an example?
Canal- tubelike passageway through bone for nerves, blood vessels
ex, mandibular canal
What is this a picture of and what is it? What is an example?
Foramen- Opening or hole in bone, nerves, blood vessels pass through
eg. mental foramen
What is this a picture of and what is it? What is an example?
Fossa- broad, shallow, depression of bone
ex. submandibular fossa
What is this a picture of and what is it? What is an example?
Sinus- Hollow space, cavity recess in bone
ex. maxillary sinus
What is this a picture of and what is it? What is an example?
Septum: A bony wall or partition that divides two spaces or cavities
Is the septum radiolucent or radiopaque?
radiopaque
Where may the septum be present?
within the space of fossa or sinus
What is this a picture of and what is it? What is an example?
Suture: An immovable joint representing a line of union between adjoining bones
ex. median palatal suture
Do sutures appear as radiolucent or radiopaque?
Thin radiolucent lines
What is this a picture of?
Incisive forman
What is this a picture of?
Superior foramina of incisive canal
What is this a picture of? What is it?
Canine Fossa (Lateral Fossa)
smooth depressed area, medial to infraorbital foramen between canines and lateral incisors
What is this a picture of? What is it?
Nasal Cavity (Nasal Fossa) Pear shaped compartment superior to the maxilla
What is this a picture of?
Floor of the nasal cavity
What is this a picture of? What is it?
Inferior nasal conchae: wafer thing curves plates of bone on lower lateral walls of nasal cavity
Is the maxillary sinus radiolucent or radiopaque above the apices of premolars and molars?
radiolucent
Is the maxillary sinus radiolucent or radiopaque at the line of the maxillary sinus floor?
radiopaque
Why is it important to get a good dental image of the maxillary sinuses when considering implants?
To determine the amount of bone to see if an impant can be placed with out hitting the sinus
What is this a picture of? What is it?
Nutrient canals in maxillary sinus: Tiny, tubelike passages in max sinus contains nerved and blood vessels to teeth and interdental areas
What is this a picture of? What is it?
Inverted Y: Lateral wall of nasal fossa and anterior border of max sinus meet above max canine
What is this a picture of?
Maxillary tuberosity
What is this a picture of? What is it?
Hamulus: Small hook-like projection of bone from medial pterygoid plate of sphenoid bone posterior to maxillary tuberosity
What is this a picture of? What is it?
Zygomatic Process- Bony projection on max that articulates with zygomatic bone
What is this a picture of?
Zygoma
What is the largest and strongest bone of the face?
the mandible
What is this a picture of? What is it?
Ramus: Vertical portion found posterior to the third molar
What is this a picture of? What is it?
Body of mandible : Horizontal U shaped portion from ramus to ramus
What is this a picture of? What is it?
Alveolar Process: Encases and supports the teeth
What is this a picture of and what is it? What is an example?
Tubercle- Small bump or nodule of bone
ex. genial tubercles of mandible
What is this a picture of?
Lingual Foramen
What is this a picture of?
Mental Ridge
What is this a picture of?
Mental Fossa
What is this a picture of?
Mandibular Canal
What is this a picture of?
Mylohyoid Ridge
What is this a picture of?
External oblique Ridge
What is this a picture of?
Submandibular Fossa
What is this a picture of? What is it?
Coronoid Process: Bony prominence on anterior ramus of mandible attachment for a muscle of mastication
What is this a picture of?
Alveolar crest
What is the alveolar crest made of?
dense cortical bone
How does the alveolar crest appear on radiographs?
radiopaque
What is this a picture of?
Lamina Dura
What is this a picture of? What is it?
Periondtal ligamnet space: space between the tooth and lamina dura
How is the periodontal ligament space seen?
continuous thin radiolucent line around the tooth
How does anterior alveolar bone look?
dense radiopaque line caries in density and shape
How does posterior alveolar bone look?
appears less dense, flatter and smoother in inter-proximal areas
less radiopaque than anterior regions
What is this a picture of?
Incisive foramen
Which of the following structures is the most radiolucent?
a. pulp
b. cementum
c. dentin
d. enamel
a. pulp
Chpt 1:
What is radiation?
Form of energy carried by waves or by a stream of particles
What is X-Radiation?
a high energy radiation produced by the collision of a beam of electrons with a metal metal target in a x-ray tube
What is radiology?
the science or study of radiation within medicine
what is an x-ray?
a beam of energy that has the power to penetrate substances and record image shadows on receptors
What is a radiograph?
an image or picture produced on a receptor by exposure to ionizing radiation: its a 2D representation of a 3D object
What is radiography?
The art and science of making radiographs by the exposure of a receptor to x-rays
Who discovered x-rays?
Wilhelm Conrad Roentgen ( pronounced “ ren-ken”)
When did roentgen discover x-rays?
1895
How did roentgen discover x-rays?
He was experimenting with cathode rays. Using vacuum tubes, and electrical current and special screen covered with a material that glowed when exposed. He found that a cathode ray tube emitted invisible rays that could penetrate paper and wood
Why did roentgen call them x-rays?
X because of the unknown
Chpt 2
What is matter?
Anything that occupies space and has mass
What happens when matter is altered?
energy results
What is an atom?
Fundamental unit of matter: all matter is composed of atoms
What two parts make up an atom?
- the central nucleus
- the orbiting electrons
How is the identity of an atom determined?
By the composition of the nucleus and the arrangements of electrons
What is the nucleus composed of?
Protons and neutrons
What charge do protons have?
Positive
What charge do neutrons have?
They carry no electrical charge
What does the number of protons and neutrons inside the nucleus determine?
The mass number (or atomic weight)
The number of protons inside the nucleus equals the number of ________ outside the nucleus.
Electrons
What does the number of protons and neutrons determine?
The atomic number
Is the nucleus affected by x-rays?
No, only the orbiting electrons
What charge do electrons hold?
Negative charge
How do electrons travel around the nucleus?
in well defined paths known as orbits or shells
Does the shell closest to the nucleus have the highest or lowest energy level?
highest
What layer or orbit of electrons may be disturbed most during dental radiography?
The outer layer
How are electrons maintained in their orbits?
By electrostatic force between the attraction of the positive nucleus and negative electrons
What is the electrostatic forces attraction between the positive nucleus and negative electrons called?
Binding energy of an electrons
What is binding energy determined by?
The distance between the nucleus and the orbiting electron
Where is the strongest binding energy located?
Closest to the nucleus in the K shell
What is the relationship between the location of the shells and the amount of binding energy?
The shells closest to the nucleus have the strongest binding energy, the farther away from the nucleolus the weaker the binding energy
What are the binding energies of orbital electrons measured in?
electron volts ( eV) or kilo electrons volts (keV)
What must the energy required to remove an electron from its orbital shell exceed?
The binding energy: Therefore removing electrons closest to the nucleus is much more difficult
What occurs when atoms combine with one another
it forms a molceule
What is a molecule?
two or more atoms joined by chemical bonds
What two ways are molecules formed?
- the transfer of electrons
- the sharing of electrons between the outermost shell of atoms
An atom with an incomplete filled outer shell will attempt to do what?
capture an electron from an adjacent atom
if the atom gains an electron while doing this what will its charge be?
negative
if the atom loses an electron while doing this what will its charge be?
positive
What is an ion?
an atom that gains or loses an electron and becomes electrically unbalanced.
What is ionization?
the production of ions or the process of the converting an atom into ions
What occurs when an electron is removed from an atom in the ionization process?
an ion pair results
What does the atom become when an electron is removed?
a positive ion
what does the ejected electron become?
a negative ion
Why is even the smallest change at a molecular level important?
may lead to big changes at the cellular level
What other factors affect the damage that may occur?
amount of ionization over an amount of time
What is radiation?
radiation is the emission and propagation of energy through space or a substance in the form of waves or particles
What is radioactivity?
the process by which certain unstable atoms or elements undergo spontaneous disintegration, or decay in an effort to attain a more balanced nuclear state
Which is used in dentistry radiation or radioactivity?
radiation
what is propagation?
transmit or to be transmitted in a particular direction or through a medium
What is ionizing radiation?
radiation capable of producing ions by removing or adding electrons into an atom
What are the two classifications of ionizing radiation?
- particulate radiation
- electromagnetic radiation
What is particulate radiation?
tiny particles of matter that posses mass and travel in straight lines at high speeds
What are the 4 types of particulate radiation?
- electrons
- alpha particles
- protons
- neutrons
Particulate Radiation: (1) Electrons: What are beta particles?
fast moving electrons emitted from nucleus of radioactive atoms
Particulate radiation: (1) Electrons: What are cathode rays?
streams of high speed electrons that originate in an x-ray tube. Electrons emitted by a manufactured device
Particulate Radiation: What are (2) alpha particles?
emitted from the nuclei of heavy metals, they exist as two protons and neutrons with out electrons
Particulate Radiation: (3) What is protons?
accelerated particles, specifically hydrogen nuclei, with a mass of 1 and a charge of +1
Particulate Radiation: (4) What is neutrons?
Accelerated particles, with a mass of 1 and no electrical charge
What is electromagnetic radiation?
propagation of wavelike energy (with out mass) through space or matter
how are electromagnetic wave arranged?
in the electromagnetic spectrum according to their energies
how is electromagnetic radiation made?
artificial or occur naturally
What are two classifications of electromagnetic radiation?
ionizing or non ionizing
In electromagnetic radiation only ______ are capable of ionization
high-energy radiations
what are electromagnetic radiations believed to move through space as?
both a particle and a wave both concepts must be considered
What is the particle concept?
charcterizes electromagnetic radiation in term of discrete bundles of energy called photons or quanta
what are photons?
bundles of energy with no mass or weight
How do photons travel?
as waves at the speed of light and move through space in a straight line
What is the wave concept?
characterizes electromagnetic radiations as waves, with velocity, wave-length and frequency being considered
what is velocity?
the speed of the wave
what is wavelength
the distance between the crest of one wave and crest of the next
what is frequency
the number of wavelengths that pass a certain point in a given time
low wavelengths have low or high frequency?
low frequency
short wavelengths have low or high frequency
high frequency
What is x-radiation in terms of energy and type of radiation?
x-radiation is high-energy, ionizing electromagnetic radiation
what are x-ray ?
weightless bundles of energy with no electrical charge that travels in waves with a specific frequency at the speed of light
x-ray photons interact with the materials they penetrate and cause __________
ionization
What part of the x-ray machine contains the x-ray tube that produces dental x-rays?
the tubehead
What is the function of the metal housing in the tubehead
surrounds the tube and transformers, protects tube and grounds high voltage components
what is the function of the insulating oil in the tubehead?
surround x-ray tube and transformers prevents over heating
What is the function of the tube head seal in the tubehead?
permits exit of x-rays from tube head, seals the oil, filters x-ray beam
What is the function of the x-ray tube in the tube head
heart of the generating system
what is the function of the transformer in the tubehead?
alters voltage of incoming electricity
What is the function of the aluminum disks in the tube head?
filter out non penetrating, longer wavelength x-rays in the tubehead
What are the 3 components of the glass vaccuum tube?
- lead glass housing
- cathode
- anode
What does the leaded glass vaccuum tube prevent/
x-rays from escaping in all directions
What purpose does the “window” on the leaded glass vacuum tube permit?
the x-rays beam to exit the tube and directs the beam toward the aluminum disks, lead collimator and PID
Is cathode negative or positive?
negative
What does the negative cathode electrode supply?
the electrons necessary to generate x-rays
What does the tungsten wire filament found in the cathode produce? how does heat affect this?
electrons when heated, the hotter the filament the more electrons are produced
Cathode: what does the molybdenum cup focus, what is it purpose?
focuses electrons into a narrow beam and directs the beams toward the tungsten target
Cathode: Where does the molybdenum cup keep the electrons? why?
near the cathode so that the instant the exposure button is pressed the circuit becomes complete and the electrons travel across the x-ray tube to the anode
are anodes positive or negative?
positive
How do electrons move? cathode to anode or anode to cathode?
cathode to anode
What does the positive electrodes in the anode do to electrons?
concerts electrons into x-ray photons
Most of x-rays (99%) are?
absorbed and given off as heat
the remaining 1% of x-rays?
leaves and is directed towards the patient
Anode: Consists of a tungsten plate embedded in a solid copper rod, What purpose does the tungsten target serve?
focal spot and converts electrons into photons
Anode: What purpose does the copper stem serve?
dissipates heat away from the tungsten target
In summary what is the purpose of the cathode?
filament is heated and emits electrons by thermionic emission
In summary what is the purpose of the anode?
angled to deflect the beam towards the filtered or collimated opening
What is the 3 simple steps of x-ray production?
A. when the filament circuit is activated the filament heats up, and thermionic emission occurs
B. When the exposure button is activated the electrons are accelerated from the cathode to the anode
C. the electrons strike the tungsten target and their kinetic energy is converted to x-rays and heat
What is the energy used to make x-rays?
electricity
what is electrical current?
a flow of electrons through a conductor
What is (DC) Direct Current?
electrons flow in one direction through a conductor
What is (AC) Alternating Current?
when electrons flow in two opposite directions
What is rectification?
The conversion of AC to DC
How does the x-ray tube head act as a self rectifier? How does this affect cathodes and anodes?
changes AC to DC while producing x-rays. Ensures current flows from cathode to anode
What is amperage?
measurement of the number of electrons moving through a conductor
How is current measured?
in amperes (A) or milliamperes (mA)
What is voltage?
measurement of electrical force that causes electrons to move from a negative pole to a positive one
What is voltage measured in?
Volts (V) or Kilovolts (kV)
What does adjusting the mA affect?
increases or decreases the number of electrons passing through the cathode filament
Was does adjusting the kilo voltage peak (kVp) affect?
controls the current passing from the cathode to anode
Can you manually change the mA and kVp?
most dental x-ray units operate at a fixed mA and kVp
what is the most often adjusted element of the x-ray machine?
the exposure time
What two electrical ciruits are used in production of x-rays
- low voltage or filament circuits
- high-voltage circuit
What is the low voltage or filament circuit
3-5 volts
regulated the flow of electrical current to the filament
How is low voltage/ filament circuit controlled
Controlled by milliamperage (mA)
What is high-voltage circuit?
- 65,000 to 100,000 volts
provides high voltage required to accelerate electrons and to generate heat
How is high voltage circuit controlled?
controlled by kV
What is the use of a transformer?
used to ethier increase or decrease the voltage in an electircal circuit
What 3 transformers are used to adjust the electrical circuits
- step-down transformer
- step up transformer
- autotransformer
What is the step down transformer?
used to decrease voltage from the incoming 110-220 line voltage to the 3 to 5 volts used by the filament (low voltage) circuit
How does the current travel with step down transformer
current travels through the step down transformer to the filament of the cathode
What is the step up transformer?
used to increase incoming voltage to 65,000 to 100,000 volts used by the high voltage circuit.
What is the autotransformer
serves as a voltage compensator that corrects for minor fluctuation in current
- Higher mA increasing filament temperature how does this effects the electrons electrons in the cathode?
more electrons are produced
- More electrons hitting the anode mean _____ x-rays leaving tube. and with ______ forcer and energy
more, greater
This produces ______ wavelengths and therefore a ______ penetrating beam
shorter, more
Why are longer wavelengths removed?
they are less penetrating and thus not useful for dental radiogrpahy
Two mechanisms of radiation ( depending on tungsten target)
- general (braking) radiation
- Characteristic radiation
What is general (braking) radiation?
makes up 85%
the term breaking refers to the sudden stopping of high speed electrons when they hit the tungsten target in the anode
What is characterstic radiation?
makes up 15%
accounts for a very small part of x-rays produced in the dental x-ray machine
this is where kinetic energy of the electrons is converted into x-rays
When an electron that passes close or hits the nucleus of a tungsten atom is slowed down, an x-ray photon of lower energy known as ________________ results
general braking radiation
When is characteristic radiation produced?
when high speed incoming electron dislodges an inner-shell electrons from a tungsten atom and causes ionization of that atom
What occurs with the remaining orbiting electrons?
they are rearranged to fill the vacancy
what does the rearrangement produce?
a loss of energy that results in the production of an x-ray photon
What is primary radiation?
the penetrating x-ray beam that is produced at the target of the anode (primary beam)
What is secondary radiation?
x-radiation created when the primary beam interacts with matter ( soft tissues of head, bones of skill and teeth)
- less penetrating than primary
What is scatter radiation?
a form of secondary radiation, the result of an x-ray that has been deflected from its path by an interaction with matter
- detremental to both patient and radiogrpaher
What are the 4 possible interaction of x-radiation
- no interaction
- coherent scatter
- compton scatter
- absorption of energy and photelectric effect
What is no interaction?
the x-ray photon passes through the atom unchanged and leaves the atom unchanged
- responsible for densities on film
what is coherent scatter?
an x-ray photon that has its path altered by matter
How does coherent scatter work?
a low energy xray photon interacts with an outer shell electron
no change in the atom occurs and a xray photon of scatter radiation is produced
the xray photon changes direction thus going unmodified
What is comptom scatter
the xray photon is deflected from its path during its passage through matter
- IONIZATION takes place
How does Compton scatter work?
an x ray photon collides with a loosley bound outer shell electron and give up part of its energy to eject and electron from its orbit
- the xray photon loses energy and continues in a different direction at a lower energy level
what is the ejected electron termed in compton scatter
compton electron
What is absorption of energy and photelectric effect?
the xray photon is completely absorbed within matter or the tissue of the patient
true or false: photoelectric effect is responsible for most of the attenuation in medical and dental radiographic images
true
what is absorption in the photoelectric effect?
the total transfer of energy from photon to the atoms of matter
what is the photoelectric effect?
an xray photon collides with a tightly bound inner shell electron and gives up all its energy to eject the electron from its orbit
when an x ray beam passes through matter it goes through a process called?
attenuation
what is it called when photons go through with out interacting?
direct transmission
- reach the receptor and show up black
which is it called when phtons are scattered by compton interaction but still go through
indirect transmission
- reach the receptor but degrade the image making it blurry and harder to see anatomy
many photons will interact with atoms in the material and be ________ by photoelectric absorption
attenuated
When attenuated do they reach the image receptor
no
What do attenuated images do
create contrast and allow up to see different structures
- shows up as white or shades of white on the image
What is radiation biology?
the study of the effects of ionizing radiation on living tissue
Does all x ray beams reach the dental x ray film?
not all some re absorbed by the patients tissues
What two mechanisms of radiation injury are possible?
- ionization
- free radical formation
When does ionization result?
when x-rays strike patient tissue
how is ionization produced? (2)
through photoelectric effect or Compton scatter
what does ionization result in?
positive atom and dislodged negative electron
How does the dislodged electron interact with other atoms
can cause chemical changes within the cell resulting in biologic damage
cell damage occurs primarily through?
formation of free radicals
how are free radicals formed?
when an x-ray photon ionizes water
What is a free radical?
an uncharged atom or molecule that exists with a single, unpaired electron in its outermost shell
- highly reactive and unstable
what can free radicals combine to form?
toxins such as hydrogen peroxide
damage to living tissue caused by exposure to ionizing radiation may result from what two things
- a direct hit and absorption of an x-ray photon within a cell
- absorption of an x-ray photon by water within a cell accompanied by free radical formation
What two therories describe how radiation damages biologic tissues
- direct theory
- indirect theory
what is direct theory?
cell damage results when ionizing radiation directly hits critical areas within the cell
- occurs infrequently, most photons pass through the cell and cause little to no damage
what is indirect theory?
when x-ray photons are absorbed by water within the cell a free radical is formed
- the free radicals combine to form toxins that damage cells
what occurs more frequently indirect or direct theory?
indirect theroy
is there a safe amount of radiation expsosure?
no
does damage occur with every exposure?
yes
what is curve used for?
to correlate the damage to tissue with the dose of radiation received
what type of relationship is seen with the curve
a linear non thresh-hold
what is a threshold curve?
indicates that below a certain level (threshold) no response is seen
what is a non threshold curve?
indicates that the response of the tissues is directly proportional to the dose
what are stochastic effects?
a direct function of the dose
no dose threshold effects do not depend on the magnitude of the absorbed dose
ex. cancer, tumours and genetic mutations
what are non stochastic (deyerministic) effects
occur after a threshold of exposure has been exceeded larger doses needed
increase in severity with increased absorbed dose
ex. erythema, loss of hair decreased fertility
What is the latent period?
the time that elapses between exposure to ionizing radiation and the appearance of observable clinic signs or symptoms
what is the period of injury?
after the latent period, a variey of cellular injuries may result ( cell death, changes in cell function)
what is the recovery period?
last event in the sequence of radiation injury
- depending on a number of factors cells can repair the damaged caused
what are cumulative effects?
effects of radiation exposure are additive
- un repaired damage accumulates in tissues
who is most susceptible for radiation injury?
children
What is total dose?
quantity of radiation received or the total amount of radiation energy absorbed
- more damage occurs when tissue absorbs large quantities of radiation
What is the dose rate rate
rate at which exposure occurs and absorption takes place
How do you calculate dose rate?
dose divided by time
extensive radiation injury occurs when? what does it damage?
large areas of the body are exposed and it damages blood forming tissues
what cells are more susceptible and sensitive to radiation
rapidly dividing cells and young cells
What is short term effects?
Associated with large doses of radiation in a short amount of time
What is Acute Radiation Syndrome (ARS)
includes nausea, vomiting, diarrhea, hair loss and hemorrhage
When do you see short term affects?
minutes, days or weeeks
are short term affects seen in dentistry?
no
What is long term effects?
small doses absorbed repeatedly over a long period of time
How long after do you see long term effects?
years, decades or generations as cancer, birth defects and genetic abnormalities
What are somatic cells?
all cells in the body expect the reproductive cells
What are genetic cells?
the reproductive cells
What are somatic effects?
seen in a person who has been irradiated- poor health, cancer, leukemia
NOT transmitted to future generations
What are genetic effects
not seen in the person irradiated but are passed on to future generations
- genetic mutations are not apparent unit the next generation
What is a radiosensitive cell?
a cell that is sensitive to radiation
what is a radio-resistant cell?
a cell that is resistant to radiation
what 3 factors determine the response of the cell being radiosensitive or radioresistant?
- mitotic activity
- cell differentiation
- cell metabolism
What is mitotic activity?
a cell that divides more frequently is radio sensitive
what is cell differentiation?
cells that are immature or are not highly specialized are more radio sensitive
what is cell metabolism?
cells that have a higher metabolism are more radiosensitive
what is the most radiosensitive cell in the body?
lymphocyte
bone, muscles and nerves are _________ cells?
radio resistant
what are some radiosensitive organs?
- lymphoid tissue
- bone marrow
- testes and female eggs
- intestines
what are some radioresistant tissues?
- salivary glands
-kidney
-liver - muscles
nerves
what is a critical organ?
an organ that, if damaged dimishes the quality of life
ex. heart, liver and lungs
what are critical organs in dental radiography?
- skin
-thyroid gland
-lens of eye - bone marrow
What is the traditional unit of radiation measurement?
Roentgen (R)
What is the newer unit of radiaiton measurement?
SI
What does Roetgen (R) measure?
the amount of ionization that occurs in air
What is the dose measurement?
the amount of energy absorbed by tissue
What is the traditional unit and what does it stand for
Rad- radiation, absorbed, dose
What is the SI equivalent
Gray
1 Gy= 100 rad
what is dose equivalent measurements used to compre?
biologic effects of different radiation
the gray and sievert are ____________ measurments
equal
the roentgen, rad and gem are considered approx ________
equal
in the US the average dose of background radiation received per year of around?
150-300 mrad per year
What is the definition of a risk?
likelihood of adverse effects or death resulting from exposure to a hazard
what is the risk of fatal cancer in dental radiography i?
3 in 1 million
is dental radiography risky?
death is more likely from common acitivies than dental images
what 4 things determine the amount of exposure a patient receives
- receptor choice- film speed, digital vs film
- collimation- rectangular collimator can reduce dose by 60-70%
- technique- increase the target receptor distance
- exposure factors
true or false 4 bite wing images is less than 1 day of backround exposure?
true, its equi alent to a short 1-2 hour flight
What is alara
as low as reasonably achievable
- all radiaiton must be kept to a minimum to protect both operator and client
why and how should dental images be prescribed?
only when the befit of disease detection outweighs the risk of biological damage. benefits far outweigh the risk
