su14_-_radiology_exam_1_20141210195314 Flashcards
What is the definition of oral and maxillofacial radiology?
the specialty of dentistry and discipline of radiology concerned with the production and interpretation of images and data produced by all modalities of radiant energy that are used for the diagnosis and management of diseases, disorders, and conditions of the oral and maxillofacial region
What is the definition of radiology?
the art and science of using ionizing radiation in diagnosis and treatment of diseases
What are the 2 subcategories of radiology?
- diagnostic radiology- therapeutic radiology (radiation therapy)
What is the definition of radiography?
the use of radiation to produce an image on a receptor
What is the definition of a radiograph?
the image produced on a receptor by exposing it to x-rays; susequent processing/developing produces a positive image in case of digital radiography and negative-like image on film
What was Wilhelm Conrad Roentgen known for?
discovered x-rays in 1895; first nobel prize in physics in 1901
What was the first radiograph taken of?
Anna Berta Roentgen’s hand
What was Dr. Otto Walkhott known for?
took the first dental radiograph
What was William D. Coolidge known for?
making the “hot cathode ray” tube
What were Sir Godfrey N. Housfield and Dr. Allan Cormack known for?
computed tomography (CT) scans
What was Nikola Tesla and Dr. Raymond Damadian known for?
improving the field strength of MRI and being the “father of the modern MRI,” respectively
What is the difference between a fluoroscope and an “x-ray”?
fluoroscope does dynamic imaging while an x-ray is a static image
Who is known as the “father of radiation protection”?
William Herbert Rollins, D.M.D., M.D.
True or false: About half of the x-ray units in the US are dental.
true
How many dental radiographs are acquired per year worldwide?
300 million
Dental radiographic examinations are second to what type of radiograph in terms of number and cost?
chest radiographs
What are the 2 types of biological effects of radiation?
- deterministic- stochastic
Which effect of radiation has a dose theshold?
deterministic
In which effect of radiation is the severity of response proportional to the dose?
deterministic
In which effect of radiation is the probability of occurence of effects dose dependent (all or none)?
stochastic
Oral changes after radiotherapy is an example of what biological effect of radiation?
deterministic
Radiation-induced cancer is an example of what biological effect of radiation?
stochastic
Radiation-induced mutations is an example of what biological effect of radiation?
stochastic
Radiation sickness after whole body irradiation is an example of what biological effect of radiation?
deterministic
True or false: Deterministic effects of ionizing radiation include short-term acute injury.
true (stochastic = long term)
What is affected in a patient’s body after it is exposed to ionizing radiation?
- biological molecules- cell structures- cell cycle- tissues and organs
What are the final products of the radiolysis of water?
- H2O2 (hydrogen peroxide)- H+ (hydrogen ion)- H2O (water)
What proportion of biological effects are caused by direct action of x-ray photons on water?
1/3
What proportion of biological effects are cuased by indirect action?
2/3
What are some effects of radiation on cell structures?
- chromosomal break- vacuolization- mitotic changes- impaired function- recovery- cell death
What are some effects of radiation on the cell cycle?
- mitotic delay (G1 arrest, G2 block)- cell death (G2 phase, M phase)
Is this the correct sequence of cell cycle radiosensitivity (the least sensitive being #1 and most sensitive #4)?1. M2. G13. G24. S
NOT correctCorrect:most sensitive: MG2G1least sensitive: S
What do short-term effects of radiation of tissues and organs depend upon?
sensitivity of parenchymal cells
What do long-term effects of radiation of tissues and organs depend upon?
the extent of damage to the fine vasculature
Do all cell types respond the same to radiation?
NO
What does the Law of Bergonie and Tribondeau state?
cells tend to be radiosensitive if they have these 3 properties:- high division rate- long dividing future- are of unspecialized type
Rank these types of cells from most radiosensitive to most radioresistant:- neurons/muscle cells- stem cells- cells of salivary gland/pancreas- spermatocytes/oocytes- endothelial cells/fibroblasts
most radiosensitive- stem cells- spermatocytes/oocytes- endothelial cells/fibroblasts- cells of salivary gland/pancreas- neurons/muscle cellsmost radioresistant
Do fine vasculature, growing bone, salivary glands, lungs, kidney, and liver have a high, intermediate, or low radiosensitivity?
intermediate
Do optic lens, mature erythrocytes, muscle cells, and neurons have a high, intermediate, or low radiosensitivity?
low
Do lymphocytes, bone marrow, testes, intestines, and mucous membrane have a high, intermediate, or low radiosensitivity?
high
What is the acute effect of radiation with an exposure of 100 Gy (Gray)?
death occurs within hours from apparent neurological and cardiovascular breakdown
What is the acute effect of radiation with an exposure of 5-12 Gy (Gray)?
death occurs within days and is associated with bloody diarrhea and destruction of intestinal mucosa (gastrointestinal syndrome)
What is the acute effect of radiation with an exposure of 2-5 Gy (Gray)?
death occurs several weeks after exposure due to damage to bone marrow (hematopoietic syndrome)
What is the acute effect of radiation with an exposure of 0.5-3.5 Gy (Gray)?
can produce varying degrees of nausea, vomiting, diarrhea, reddening of skin, loss of hair, blisters, and depression of immune system
What is the acute effect of radiation with an exposure of 1 Gy (Gray)?
mild radiation sickness, depressed white blood cell count (prodromal symptoms)
What is the acute effect of radiation with an exposure of 0.25 Gy (Gray)?
erythema, blistering and residual smooth, soft, depressed scar
True or false: A study has shown that there can be effects of genetic mutation from radiation used in diagnostic radiology.
FALSE. Currently, there is no evidence of genetic mutation from a radiation used in diagnostic radiology. (most genetic effects have been observed in atomic bomb survivors)
What is the most important somatic effect of radiation exposure?
radiation-induced cancer
Do the bladder, liver, thyroid, skin, cortical bone, brain, and salivary glands have a high, moderate, or low susceptibility to radiation-induced cancer?
low
Do the breast and esophagus have a high, moderate, or low susceptibility to radiation-induced cancer?
moderate
Do the colon, stomach, lung, and bone marrow have a high, moderate, or low susceptibility to radiation-induced cancer?
high
What does ALARA stand for?
As Low As Reasonably Achievable
What are the 3 key points of ICRP recommendations (ALARA)?
- no practice shall be adopted unless its introducation produces a positive net benefit- all exposures shall be kept as low as reasonably achievable- the dose equivalent to individuals shall not exceed the limits recommended
What is the annual occupational limit for human exposure to ionizing radiation?
50 mSv
What is the annual non-occupational limit for human exposure to ionizing radiation?
1-5 mSv
True or false: The probability of occurence of radiation-induced cancer increases with an increase in dose.
true
Who is more radiosensitive for cancer induction: children or adults?
children
What is the risk of dental radiography in terms of inducing cancer?
approximately 20% of the population die of cancer; estimated risk from dental radiography is approximately 2.5 extra fatal cancers per million dental radiographic examinations
What are the two effects (direct and indirect) of radiation on biological molecules?
- free radical production- radiolysis of water
What are the 2 main attributes of x-rays?
- ionization- excitation
What is the definition of ionization?
ionization occurs when an atom gains or loses an electron; occurs when particulate or electromagnetic radiation energy is greater than the binding energy
During ionization, is the ejected electron a positive or negative ion? Is the remainder of the atom a positive or negative ion?
- ejected electron: negative ion- remainder of atom: positive ion
What is the name of the radiation that causes ionization (usually in biologic molecules)?
ionizing radiation
What is the definition of excitation?
when the transferred energy is not sufficient to overcome the binding energy, the electron is not ejected from its orbit; electron receiving the extra energy is raised to a higher energy level within the orbit and then instantaneously gives up this excess energy and returns to its normal energy level
What property of x-rays causes its effects?
the ability to ionize
What is the penetrability of x-rays related to? Is it related to each directly or inversely?
- photon energy: directly- number: directly- atomic number, thickness, and density of absorber: inversely
Name the 3 salient properties (effects) of x-rays.
- photographic effects- fluorescent effects (useful in intensifying screens)- biologic effects
True or false: X-rays are invisible, highly penetrating electromagnetic waves.
true
What is the charge of an x-ray? Why is this significant?
neutral charge; cannot be deflected by electrical or magnetic field
Are x-rays heterogeneous or homogeneous?
heterogeneous (variable wavelengths and energy photons)
True or false: X-rays radiate from source in curved lines and tend to diverge from focal spot.
FALSE. X-rays radiate from source in STRAIGHT LINES.
Are x-rays capable of ionizing gases?
yes!
At what speed do x-rays travel?
speed of light
True or false: X-rays cause fluorescence of certain crystals.
true
What is the useful wavelength range of an x-ray in dentistry?
0.1-0.5 oA
True or false: X-rays produce a latent image on an image receptor which can be processed.
true
What type of radiology are low energy x-rays used for? High energy x-rays?
- low energy: diagnostic radiology- high energy: radiation therapy
What is the inverse square law?
intensity (amount or quantity) of radiation is inversely proportional to the square of the distance between the source and point of measure
What are the 3 primary means of x-ray beam absorption?
- photoelectric absorption- comptom scattering- coherent scattering
What percentage of primary photons pass through without any interaction?
9%
What occurs during photoelectric absorption?
incident photon interacts with an inner shell electron (usually in a K shell) and overcomes the binding energy; electron is ejected (ionization) which is called photoelectron or recoil electron; ejected electron acquires the remainder of the KE
What other ionizations can be caused by a photoelectron?
secondary and tertiary ionizations
What does absorption depend upon for photoelectric absorption?
absorption depends upon atomic number of the object; the greater the number, the greater the absorption
True or false: Radiography is based on absorption of only one material.
FALSE. Differential absorption by different materials makes radiography possible.
Describe Compton absorption.
incident photon interacts with an outer electron and overcomes binding energy to eject the electron (ionization); ejected electron (called a Compton electron) acquires part of KE and the remainder of the energy is given off as a scattered photon
True or false: Compton electron cannot cause secondary or tertiary ionization.
FALSE. Compton electron CAN cause secondary or tertiary ionization.
What is Compton absorption a major source of?
major source of scatter radiation
Describe coherent scattering.
low energy photons (less then 10 keV) pass near outer electron of an atom; electron vibrates at the same frequency as incident photon; entire energy given off as scattered photon which is usually absorbed by the tissues
What are the 2 main components of radiographic film?
- base- emulsion
What are the properties of the base of radiographic film?
- polyester- supports film emulsion- flexible (to allow film handling), translucent, chemically inert, and tinted blue to enhance contrast- 0.125-0.225 mm thick
What are the properties of the emulsion of radiographic film?
- silver nitrate and potassium bromide in gelatin form AgBr crystals- a small amount of potassium iodide and trace amount of silver sulfide are added to increase sensitivity of emulsion- emulsion is coated on both sides of the base
What is emulsion sensitive to? (hint: 8 things)
x-rays, chemicals, light, pressure, heat, static electricity, humidity, and aging
How is a latent image formed on a film?
- image forms in emulsion when it is exposed to x-rays or light- the AgBr in the emulsion forms metallic silver when exposed to x-rays and constitutes the latent image- the metallic silver is chemically processed to form a radiograph
What causes radiographic fog?
radiographic density produced by causes/sources other than the primary beam of radiation; it reduces the radiographic contrast
What are the 4 types of radiographic fog?
- emulsion fog- chemical fog- scatter radiation fog- safelight fog
What is the cause of emulsion fog?
due to AgBr crystals made developable by catalytic action of contaminants in the emulsion
What is the cause of chemical fog?
due to development of unexposed AgBr crystals due to impurities in the developer solution
What is the cause of scatter radiation fog?
due to exposure of film by scatter radiation; it is the most common cause of film fogging
What is the cause of safelight fog?
due to exposure of film by unsafe safelight; 100% avoidable
What is the most common cause of film fogging?
scatter radiation fog
Which type of radiographic fog is the most easily avoided?
safelight fog
What is the definition of speed in terms of radiographic film?
the ability of a film to produce certain radiographic density with lesser or greater amount of radiation
Does a higher speed film require more or less radiation?
less radiation
What is the advantage of a high speed film? Disadvantage?
- advantage: substantially reduce patient exposure- disadvantage: less image sharpness due to larger size (tabular shape) of AgBr crystals
What is the definition of spatial resolution?
the ability to record separate images of very small objects placed very close together
What is the spatial resolution of intraoral film? Of intraoral sensor?
- intraoral film: more than 20 line pairs/mm- intraoral sensor: 25 line pairs/mm
What are intensifying screens used for? Why are they beneficial to patients?
to intensify photographic effect of x-rays by converting them into visible light; reduce radiation exposure of patients by 10-60 times
What is the purpose of a cassette?
- serve as holders for intensifying screens- screens are always used in pairs (one for each leaf of the cassette)- films with emulsion coated on both sides are used- tight screen film contact is essential for sharp image
What is the intensification factor for intensifying screens?
10 (10 times less radiation to patient)
What type of film is the American National Standards Institute (ANSI) used to classify?
intraoral films
What are the different classifications for the ANSI system?
- to the left of the decimal: - 1 = periapical - 2 = bitewing - 3 = occlusal- to the right of the decimal: - size
What are the standard adult periapical? Standard adult bitewing? Standard adult occlusal?
- standard adult periapical: 1.2- standard adult bitewing: 2.2- standard adult occlusal: 3.4
What is the difference between intraoral and extraoral radiographs?
- intraoral: receptor placed inside the oral cavity- extraoral: image receptor placed outside the oral cavity
What are the 3 types of intraoral radiographs?
- periapical (PA)- bitewing (BW)- occlusal
What is included in a periapical radiograph?
- more emphasis on tooth (teeth) apex and area around the tooth apex- generally, must record entire crown, root, and 2-3 mm periapical area- if anatomically not possible (ex. teeth with long roots), the image of crown may be sacrificed
What is needed to take a periapical radiograph?
- intraoral image receptor- positioning instrument- an x-ray source- an x-ray channeling device
What is included in a bitewing radiograph?
records crowns of maxillary and mandibular teeth and alveolar crest
What is a bitewing radiograph used to assess?
- alveolar crest (marginal periodontal bone loss)- caries (especially interproximal)
What are the 2 types of occlusal radiographs and what are each used for?
- topographic occlusal: for assessing anterior jaw and associated dentition- cross-sectional occlusal: for assessing whole body of jaw
What are the indication for an extraoral radiograph?
- when the area to be imaged is larger than could be covered by an intraoral image receptor- pathological process is located in an area not normally covered by in intraoral image receptor- trismus (lockjaw)- extreme gag reflex- growth and development- facial trauma- multiple lesions
What are the 3 types of extraoral radiographs?
- lateral cephalometric and head view- posteroanterior view- panoramic view
Medical exposures account for approximately how much of the population dose to radiation?
half of the population dose to radiation
What is the primary driver of radiation?
CT scans
What are the 3 aspects to radiation protection?
- patient protection- operator protection- office personnel/general public protection
By how much is radiation reduced with a digital receptor as opposed to film?
by half
Which is better in terms of less radiation: digital or film?
digital
Which is better in terms of less radiation: slower speed film (D) or faster speed film (E/F)?
faster speed (E/F)
Which is better in terms of less radiation: rectangular or round collination?
rectangular
Why is rectangular collimation better?
rectangular collimation optimizes the shape of the field of view to minimize exposure to healthy tissues
Which is better in terms of less radiation: a longer or shorter cone?
longer because it concentrates the x-rays into the area that needs to be radiographed
What does a lead apron and thyroid collar protect against?
protects against scattered radiation
Who should hold the image receptor: the patient or the operator?
Trick question! Neither! Use a positioning device.
What are the 3 reasons to use a positioning device?
- ease of use- stability- reduces radiation exposure
True or false: If needed, patient’s guardian may hold the image receptor.
true
Who should hold the tube head: the patient or the operator?
Trick question! Neither! Tube head should be stable unassisted.
True or false: Leakage radiation is another name for scattered radiation.
FALSE. Leakage radiation and scattered radiation are not the same thing.
What are 2 things to keep in mind about using portable dental x-ray units in a practice?
- not legal in all states (but legal in Ohio)- special procedures are required to ensure safety
What 2 skills are required for proper use of radiographs?
- radiographic technique skills (important to take a good radiograph)- radiographic interpretation skills (important to be able to interpret the radiograph)
What is the definition of a primary protective barrier?
a barrier of radiation-absorbing material used to reduce radiation exposure to primary or usable beam of radiation
What is the definition of a secondary protective barrier?
a barrier of radiation-absorbing material used to reduce radiation to secondary and leakage radiation
If the operator cannot leave the room when an x-ray is being taken, how far away should they stand?
6 feet (inverse square law)
If the operator cannot leave the room when an x-ray is being taken and has no barrier, where should they stand?
90-135 degrees to the central ray
What is the purpose of a structural shielding design?
to ensure that dentist, auxiliary personnel, and other people in the vicinity of the dental office are not exposed to radiation exceeding certain limits
How can structural shielding design be accomplished?
- conventional building materials may provide adequate radiation shielding for dental radiographic equipment- increasing thickness of building materials in the walls, ceiling, or floor- lead, concrete, steel, etc.
What are the 4 ways to monitor personnel for radiation exposure?
- film badges- TLD chips- OSL dosimeters- commercial services (NVLAP accredited services)
True or false: Use of radiation badges to monitor exposure is an active measure of assurance that radiation exposures of the staff are low.
FALSE. Use of radiation badges to monitor exposures is a PASSIVE measure of assurance that radiation exposures of the staff are low.
Which is more important and should take the “lead role” in radiation safety: active or passive radiation protection?
active (technique, engineering controls, procedures)
What are the 2 ways radiation safety is accomplished for office personnel and general public protection?
- engineering controls/facility design- structural shielding design
What are the 2 special people to be extra aware of radiation safety for?
- pregnant personnel and pregnant patients- children in the thyroid region (because their thyroid contains actively dividing cells)
What are the 5 steps of manual film processing?
- development2. rinse3. fixation4. wash5. dry
In manual film processing, describe the apparatus used (ex. the material the tanks are made of, the liquid inside, etc.)
- tanks for chemicals are usually stainless steel- placed in a larger tank filled with running water- water serves as a rinse and maintains the required temperature
What is the purpose of the water in manual processing of film?
- rinse- maintaining the required temperature
What are the advantages (3) of manual processing of film?
- cheap- lasts “forever”- easy to maintain
What are the disadvantages (4) of manual processing of film?
- temperature is not regulated- need time-temperature chart- drying cabinet- developer contamination
What are the advantages (3) of rapid processing of film?
- no dilution necessary- instant (develops in 15 seconds and fixes in 15 seconds at room temperature)- can have it chair-side
What are the disadvantages (6) of rapid processing of film?
- solutions last up to 2 days (or 60 films) before oxidizing (thus supplied in small bottles)- usually used with chair-side darkroom (have to avoid light leaks or cross-infection)- sensitive to variables, especially time- lower contrast- may discolor over time- after viewing, rapidly processed films should be placed in conventional fixing solution for 4 minutes and washed for 10 minutes
What are the 4 steps of automated processing of film?
- development2. fixation3. wash4. dry
What are the advantages (3) of an automated film processor?
- time saver: 4-6 minutes/cycle- consistent density and contrast (less human variables)- day light loader eliminates the need for a dark room (a back up dark room is advisable)
What is the purpose of sulfate in an automated film processor?
sulfate added to minimize the swelling of the emulsion so the films can be transported by the rollers uniformly
What would occur if manual processing developer solution was placed in an automated processor?
film emulsion will most likely stick to the rollers and damage the radiographic image
True or false: Dent-X automated film processors is a continuous feed processor and can process sizes 0, 1, 2, 4, and panoramic films.
true
How does the SRX-101A differ from the Dent-X automated film processor?
SRX-101A has:- continuous automatic replenishment- attached to sink- larger films can be processed
What are the 7 processor systems in automated film processor?
- transport system- temperature control system- circulation/filtration system- replenishment system- dryer system- electrical system- chemical system
What are the 3 types of darkroom design?
- maze-type entry- double-door type (spring-mounted door)- revolving door type
What are the two types of safe light filters for a dark room?
- GBX2 (ruby red) filter: safe for intraoral and extraoral films- ML-2 (orange): unsafe for panoramic radiographs
Which safe light filter is not safe for panoramic radiographs?
ML-2 (orange)
What are the 3 factors of a dark room safe light?
- color- wattage- distance
True or false: Red safe light is not safe for intraoral films.
FALSE. Red safe light is safe for intraoral films.
What is the general wattage of safe light?
7.5-15 watts
Where is the best location for a safe light? (ex. distance, location, etc.)
- distance: 4 feet from the surface where films would be handled- best place: to the right of fixing tank
Describe the test for safeness of a dark room.
place a coin on an unexposed and unwrapped film (2 minutes); process the radiograph as usual; if outline of coin is present, the safelight is broken
What is the definition of radiation?
the production and emission of energy through space or a material medium
What are the 2 types of radiation? Give examples of each.
- particulate (corpuscular) radiation: protons, neutrons, electrons, alpha/beta particles, etc.- electromagnetic radiation: radio, TV, radar, infrared, visible light, UV, gamma rays, x-rays, etc.
Electromagnetic (EM) waves, also known as electromagnetic radiation, are grouped according to wavelength in the ____.
electromagnetic spectrum
True or false: EM waves have a mass and an electrical charge and travel in a wave-like motion at the speed of light.
FALSE. EM waves have NO MASS and NO ELECTRICAL CHARGE and travel in a wave-like motion at the speed of light.
Which has a higher associated energy and frequency: shorter or longer wavelengths?
shorter wavelengths
Do x-rays have wavelengths shorter or longer than ultraviolet? Than gamma radiation?
- shorter than ultraviolet- longer than gamma radiation
True or false: X-rays are composed of photons, or packets, or weightless bundles of energy.
true
Describe how x-rays are produced.
- highly accelerated electrons are suddenly brought to a stop by hitting a stationary object- a fraction of the kinetic energy possessed by the high-speed electrons is converted to x-rays
The nucleus makes up what percentage of the mass of an atom? What charge does it carry?
- 99.998% mass of atom- positive charge
Orbital electrons make up what percentage of the mass of an atom? What charge does it carry?
- 0.002% mass of atom- negative charge
What particle of a nucleus of an atom determines the identity of an element?
proton
What is the charge (positive/negative) of a proton? What is the magnitude of that charge?
positive charge equal in magnitude to negative charge of electron
What is the charge of a neutron? Is it heavier or lighter than a proton?
- no charge- slightly heavier than a proton
What is the Z number (atomic number) equal to? What does the Z number determine?
- the number of protons- determines the identity of an element
What is the A number (atomic mass) equal to?
number of protons + number of neutrons
When writing the atomic symbol, is the Z number a subscript or superscript? The A number?
Z number = subscriptA number = superscript
What is the charge of an electron? What is the magnitude of that charge equal to?
negative charge equal in magnitude to the positive charge of a proton
How are the electrons arranged around an atom?
arranged in definitive energy levels (shells/orbits) outside the nucleus at varying distances
How are electrons kept in orbit around the atom?
electrostatic attraction and centripetal force
How are the orbits of an atom lettered/numbered? What is the maximum number of orbits in a given atom?
- lettered: K, L, M, N, O, P, Q; numbered: 1, 2, 3, 4, 5, 6, 7- maximum number of orbits in a given atom is 7
True or false: The maximum number of electrons in each orbit are unlimited.
FALSE. The maximum number of electrons in each orbit is LIMITED (K=2, L=8, M=18, N=32, etc.)
What is the definition of binding energy?
the attractive force that keeps electrons in their orbit
True or false: Binding energy is INVERSELY proportional to the square of distance between nucleus and electron.
true
Which are most tightly bound: K shell electrons or the outermost shell electrons?
K shell electrons
When moving an electron from outer orbit to one closer to the nucleus, energy is lost in the form of ____.
electromagnetic radiation
What shells are the electrons in that are involved in x-ray, gamma ray, and high energy particle production?
K, L, and M shells
What shells are the electrons in that are involved in production of ultraviolet light, visible light, etc.?
outer shells
Which binding energy is higher: an atom with a higher Z number or an atom with a lower Z number?
higher Z number
What are the 2 types of radiation?
- particulate radiation- non-particulate radiation
How is energy transferred in particulate radiation? In non-particulate radiation?
- particulate: transfer of energy by high velocity subatomic particles (protons, neutrons, alpha/beta, electrons)- non-particulate: transfer of energy through space as a combination of electrical and magnetic fields
What type of energy is associated with particulate radiation?
kinetic energy
Is kinetic energy directly or inversely related with the mass of the particle? With the velocity of the particle?
directly related to both the mass and velocity of particle
Which type of radiation (particulate/non-particulate) is used mostly in radiation therapy?
particulate
What is the definition of Linear Energy Transfer (LET)?
rate of loss of energy of a particle as it moves along its path in an absorber
Is the Linear Energy Transfer related directly or inversely to the mass of the particle? The charge of the particle? The velocity of the particle? The chemical composition (Z#), thickness, and density of absorber?
- mass of particle: directly related- charge of particle: directly related- velocity of particle: inversely related- chemical composition (Z#), thickness, and density of absorber: directly related
What are the 2 theories of non-particulate radiation? Describe each.
- wave theory: energy (electromagnetic radiation) is transferred in the form of waves- quantum theory: energy (electromagnetic radiation) is transferred in the form of bundles or packets of energy called photons or quanta
True or false: Electromagnetic radiation travel in ALL directions from its source, according to wave theory.
true
What is the definition of a wavelength? What unit is used to measure it?
- distance between two successive crests or troughs- measured in meters, or in the case of x-rays, in Angstrom units (1A = 10^(-10)m)
What is the definition of frequency in the wave theory?
the number of oscillations, vibrations, waves, or cycles per second
What is the velocity of waves equal to? (hint: formula)
velocity (c) = wavelength (lambda) x frequency (v)
True or false: Velocity of ALL electromagnetic radiations in the air is the same.
true (3x10^10 cm/sec?)
Energy and velocity of an electromagnetic wave are directly or inversely related?
directly related
Energy and wavelength of an electromagnetic wave are directly or inversely related?
inversely related
What are the 2 mechanisms of x-ray production? (hint: electron to ___ interaction…)
- electron to nucleus interaction (bremsstrahlung)- electron to electron interaction (characteristic radiation)
What mechanism of x-ray production is described?high velocity electrons are suddenly decelerated (stopped or slowed down) at the target; complete or partial conversion of electron kinetic energy to x-ray energy (photon) measured in keV
bremsstrahlung (“braking radiation”)
What are the 3 requirements for Bremsstrahlung x-ray production?
- electrons- high velocity (electrons)- high Z number absorbing material/target (ex. Tungsten 74W)
What is the formula the relates kinetic energy to mass and velocity?
KE = (1/2)mV^2
True or false: All electrons attain the same velocity.
FALSE. All electrons do not attain the same velocity - some move at higher velocities than others.
Explain how Bremsstrahlung x-ray production produces a continuous spectrum (varying energy levels) of x-ray photons.
- some electrons striking the nucleus suddenly stop and give up all of their KE and a single high energy x-ray photon is produced- most electrons pass close to the nucleus, decelerate and give up some of their KE, producing x-ray photons with varying energies
True or false: Bremsstrahlung x-ray production produces a polychromatic (heterogeneous) x-ray beam.
true
What percentage of a diagnostic x-ray beam is Bremsstrahlung?
70%
What mechanism of x-ray production is described?incident electrons interact with K (or L) shell electrons of target (tungsten) atoms, overcome the binding energies, and cause ionization; when a K-shell electron is ejected, replacement occurs from L, M, or N shell or a free electron
characteristic radiation
In characteristic radiation, a photon representing ___ is produced.
representing the binding energy difference of two electrons
Does characteristic radiation produce a homogeneous or heterogeneous x-ray beam? Is it more narrow or more broad in its energy spectrum than Bremsstrahlung?
- heterogeneous x-ray beam- much narrower energy spectrum than Bremsstrahlung
What percentage of a diagnostic x-ray beam is made up by characteristic radiation?
30%
What is the primary source of energy for an x-ray tube?
electricity
What is the kilo voltage peak (kVp) responsible for?
the kilo voltage peak (kVp) is responsible for the speed of the electrons and thus the energy of the x-ray beam
What is the purpose of the cathode? Is it the positive or negative electrode?
- to supply electrons through a heated filament- negative electrode
What is used to contain and direct the electrons of the cathode?
molybdenum focusing cup
What is the purpose of the anode? Is it the positive or negative electrode?
- to stop the high energy electrons and to convert their kinetic energy into x-rays- positive electrode
Is the anode or cathode described below?- low voltage circuit- filament is made of tungsten wire- molybdenum focusing cup- electron cloud (“boiled off” electrons)
cathode
Is the anode or cathode described below?- high voltage circuit- angled tungsten target/focal spot- heat absorber/radiator
anode
What is the target/focal spot made of? What are its actual dimensions? What is the size of the effective focal spot it produces?
- made of tungsten embedded within the copper anode- measures about 1x3 mm (actual dimensions)- angulated to produce a beam from a smaller area of 1x1 mm (effective focal spot)
Why is tungsten used as a target? (hint: 6 reasons)
- high melting point and heat stability (won’t melt easily)- high ductile material- produces predictable and optimal energy x-rays for penetration of bone and dental tissues- high atomic number (produces characteristic photons with a predictable and useful level of energy)- high thermal conductivity- low vapor pressure
What percentage of the energy produced by an x-ray tube is heat? How is this heat kept from overheating the target?
- over 99% of the energy produced is heat- copper stem of anode and oil immersion of the x-ray tube reduce overheating of the target
What is the purpose of the portal in an x-ray tube? The filter?
- portal: channel for passage of x-rays- filter: made of aluminum; absorbs less penetration (long wavelength/soft/less energetic) x-rays which are harmful to patient
What is the fate of x-rays with longer wavelengths when taking a diagnostic x-ray?
if they are not absorbed by the filter, they are mostly absorbed by the skin and do not reach the target tissues (teeth, bone, etc) and can produce secondary radiation that will fog the film
What is the definition of the Half Value Layer (HVL)?
the thickness of aluminum in the filter of an x-ray tube that will reduce the number of x-ray photons passing through it by one half or 50%
How does rectangular collimation reduce patient exposure to primary radiation?
it shapes the beam to the shape and size of the image receptor
True or false: Collimation facilitates beam and receptor alignment.
FALSE. Collimation shapes the beam to the shape and size of the receptor, but POSITIONING INSTRUMENTS facilitate beam and receptor alignment.
Describe thermionic emission.
the filament current (low voltage) heats up tungsten filament (at cathode) to incandescence which results in the separation of outer electrons of its atoms; this process is much like a light bulb
Describe, in too much detail, the steps in the production of x-rays between a cathode and anode.
- filament current (low voltage) heats up the tungsten filament (at cathode) to incandesence which separates the outer electrons of its atoms (“thermionic emission”)- as the electric current flows, the tungsten filament gets hotter and an electron cloud is produced at the filament- the electron cloud electrons become more active and, by random collisions, produce more free electrons- a small molybdenum collar (focusing cup) at the cathode serve to concentrate the electrons- when the high voltage circuit (at the anode) is activated, these concentrated electrons form a beam that hits a small area (focal spot) located on the face of the copper anode- high potential difference is created (by pressing the exposure switch on the control panel) between the filament cathode and the target anode by activating a high voltage circuit at the anode- electrons which have been “boiled off” at the filament will rush toward the anode at a high speed- kinetic energy of the electron stream interacts with the tungsten target and undergoes conversion - 99% is given off as heat -
What does the control panel of an x-ray machine control? (hint: 3 things)
- milliamperage (current)- exposure time- kilovoltage (power)
What are the 8 factors influencing radiographic image?
- control panel (milliamperage/current, exposure time, kilovoltage/power)- density, contrast, and resolution- distortion- filtration and collimation- distance between source and receptor- distance between object and receptor- object attenuation (absorption) depending on: density, atomic number, and thickness- penetrability of x-rays (photon energy, thickness of the object, density of the object)
True or false: Object density and image density are completely different.
true
What are the 4 interactions of x-rays with matter?
- complete absorption of the beam by the object (photoelectric absorption)- almost complete absorption (coherent/thompson scattering)- complete penetration to receptor- scatter: partial/tangential exposure of receptor (compton scattering)
When x-rays are absorbed completely by the patient, what type of image is produced?
white/clear/radioopaque areas on the image
When some x-rays pass completely through the patient without loss of energy, what type of image is produced?
black/dark/radiolucent areas on the image
When some x-rays are scattered in a new direction, what type of image is produced?
fog
