Glossary of Oral Radiology 2
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- Who discovered X radiation?
- Wilhelm Conrad Roentgen
Director of Physics
Nov 8, 1895
- What did Welhelm Conrad Roentgen discover?
- 1859-95 he experimented with partially evacuated glass tubes (Crooks Tube)
e- flowed from anode to cathode with hi voltage
- What did Roentgen observe at the end of the Crooks tube?
- illumination bc it was coated with Fl
- Instantaneous emission of light.
- Substance that causes fouorescence
emits green, yellow light
- What caused Fluorescence?
- Due to unknown ray that penetrated glass and paper
Unknown rays were called X rays
- When did roentgen perform first x ray?
- Dec 1895
of bertha's hand
exposure time of 15 min
- Who won first nobel physics prize?
- in 1901. Roentgen
- When did Roentgen die?
- 1923 at 78 yrs old
- Who first made dental radiograph?
- Dr. Otto Walkhoff did first dental xray of patients jaw usuing photographic emulsion wrapped in paper with rubber dam. exposure time of 25 min.
- First dental radiograph in US
- William Rollins DDS
- Edmund Kells
- 1896 New Orleans
Developed film holder to hold glass plate
Exposure time 15 min
- first to pay price for poor radiation hygience
- Edmund kells
hands were exposed to tube chronically when setting the tube so he got ulcers
- In early days, what influenced the the quality and quantity of Xrays?
- How did edmund kells die?
- "BULLET TO THE BRAIN"
- Howard Raper
Introduced Dental Radiology Book
Invented Bitewing film 1926
- When were bitewings developedD?D
- 1926 by Howard Raper
- Will David Collidge
- Born in Mass.
Worked and studied at MIT
developed a new evacutated xray tube which allowed xrays to have a consistant exposure time and quality
Also his work with Tungston filament played a big role in development of modern xray
- Where is current applied fro xray?
- to cathode to make free electrons. xrays are made when the reapidly moving e- are suddenly stopped as they strike metal target of tube
- Uses of Xrays
- med-diagnosis and treatment
- How do xrays make image?
- xrays are transmitted through the object, they ineteract with the xray film emulsion and make an invisible image
- objective of dental xray
- obtain accurate info to aid in diagnosis
- intraoral radiography
- film inside patients mouth and xray source is outside
- extraoral radiography
- film and xray sourc outside the patinets mouth
- Number of intraoral film sizes
- Size 3 film
- used for bitewings
- Sze 4 film
- used for occlusal radiography to look at the whole arch
- Size 1 film
- placed vertically used to take pic of anterior periapical (PA) xray
- Size 2 film
- placed horizontally used to take posterior periapical (PA) xray
- periapical film
- show the entire tooth and its surrounding structures
establishes: root/crown ration, root morph, and to evaluate the status of the periapical bone.
- What do periapical films show?
- the entire tooth and its surrounding structures
- shows crowns and necks of teeth and supporing marginal alveolar crestal bone of both arches simultaneously
- Purpose of Bitewing
- 1. detect decay on proximal surfaces of coronal and cervial regions of teeth
2. to examine the interproximal crestal bone
- Occlusal radiograph
- shows large area of either maxilla or mandible
useful for fractrue, path, root fragments, and unerupted teeth
- Advantage and disadvantage of extraoral radiograph
- advantage- broad anatomical coverage
Disadvantage- lack of fine anatomical detail
- sagital plan
- divides r and l
- coronal plane
- divides front from back
- Axial plane
- diviedes top from bottom
Example" amalgum stops radiation completely so it is radioopaque. so is bone
- Dark/ black
Soft tissue in root canal
- physical manifestition
occupies space and has inertia. has mass. can be a solid, liquid or gas
- 2 divisons of matter
- elements and compounds
- smallest part of an element
- smallest part of an element. cant be subdivided by ordinary chem means
can only be broken into subatomical particles by hi energy
- protons and neutrons within the nucleus of an atom
- transmission of enery through space and matter. Xrays penetrate tissue
- Atomic number Z
- number of protons in nucleus or number of e- in nuetral atom
- mass number
- number of nucleons, protons plus neutrons
- How are electrons held in place?
- by electrostatic forces of positively charged nucleus
- Electron binding energy
- energy required to remove an e- from its orbit.
energy that must be supplied to pull e- away from atom
- what happens as e- jump from lower energy to higher energy shelll?
- release e-
- inner shell e-
- closely bound to nucleus bc more forces are acting on them so higher energy. binding evergy is much higher in the inner shell
- What causes binding enery to remove e-?
- x ray
- when a neutral atom acquires a charge
- what is required to overcome the electrostatic forces that bind the electrons to the nucleus
- what is a form of energy that forms a ion pair
- two types of radiation
- particulate radiation
- atomic nuclei or sub atomic particles moving at hi velocity.
Example: alpha and Beta particles, cathode rays
- Alpha particles
- type of particulate radiation
composed of 2 protons and 2neutrons so + charge. emitted from nuclei of heavy metals. Densely ionized matter with lo penetration. gives off large energy within a short distance
- are alpha particles bad?
- yeah because they give off energy densely and quickly in one area so destroys cells
- Beta particles
- neg charge
Emerge from nucleus of radioactive atom. more penetrating that alpha and less densely ionizing.
- Cathode rays
- neg chare
originate from xray tube
more penetrating than alpha particle and less densely ionizing
- Linear Energy Transfer LET
- rate of loss of enery from the particle as it moves throught the matter
- LET of alpha particle
- hi bc all energy is given off in a small area
- LET of beta particle
- lo LET bc gives off energy more slowly over a larger area than alpha
- Electromagnetic radiation
- proopagation of energy through space accompanied by electric and magnetic fields
- when is electromagnetic radiaion generated?
- when velocity of an electrically charged particle is changed
- Examples of electromagnetic radiation
- radio waves
- where do gamma rays originate from?
- atomic nucleus
- Where do x rays originate from?
- orbiting electrons
- two theories of interactions of electromagnetic radiation
- 1. particle concept
2. wave concept
- 2 types of x radiation
- ionizing and electroradiation
- Particle concept of electromagnetic radiation
- particles are discreate bundles of energy with NO mas and travel and speed of light carring a specific amount of energy
- Wave concept of electromagnetic radiation
- propagation of wave enery through space at speed of light. electric and magnetic fields move forward like ripples. exhibits properites of wavelength and frequency
- distance between crests of two waves
- Wavelenght frequency correlation
- when waveleght long, lo frequency, less penetration
when wavelenght is short, hi frequency, more penetration
- number of waves passing through a point per second
- What characterized hi energy photons?
- What characterizes lowere energy photons like radio waves
- When are electromagnetic radiations considered to be ionizing?
- if they have a photon energy in excess of 124 eV which is a wavelength of 10-6 cm
- Properties of Xrays
- cant see hear or smell
no mass and no charge
travel in straight line
diverge from source
can be straight line
make chem and bio changes in tissue
- Can xrays be focused on a point?
- no just an area
- how are xrays absorbed?
- differentially absorbed. all shades of gray, white, blck based on diff tissues with diff densities
- is fat radiolucent or opaque?
- periodontal lig radiolucent or opaque?
- Describe Xray beam?
- heterogeneous and has certain quality and quantity
- What influences beam intensity?
- exposure time
beam energy kVp
Source film distance
- What is effected by bean intensity?
- number of xray photons produced
Energy of xray photons
mean energy of bean
max energy of beam
- What happens as exposure time increases but mA and kVp are held constant?
- no of photons increase
mean photon nrg is unchanged
max phonton nrg is unchanged
- How many impulses in one sec?
- What happens as mA increases?
- No of photons increase
mean nrg unchanged
max nrg unchanged
Same results as increasing exposure time
- What happens as tube voltage kVp increases
- increases max nrg of photons
increases mean nrg of photons
increases no. of photons made
- what does mA control?
- what does kVp control/
- half value layer
- thickness of absorbing materials (al)required to reduce the intensity of the beam to one half its original value
- what happens to HVL as average energy of xray beam increases?
- Large HVL
- Hard radiation more penetration through tissues
- small HVL
- Solt radiation
Less penetration through tissue
Radiation is easily absorbed
- If kVp increases from 50 to 100 how much will xray intensity increasee?
- by 4
- what does increased intensity result in on the film?
- reducing intesity of beam by selectively removing the longer wavelength less penetrating photons by using Al filters
- What happens as filtration increases?
- no of photons decrease
mean energy increases
max nry is unchanged
- types of filtration
- 1. inherent filtration
2. added filtration
3. total filtration add 1 & 2
- Inherent filtrating
- photons are absorbed by:
glass wall of xray tube
Barrier material to prevent oil leakage
- Added filtration
- used bc inherent filtration is not enough to meet standards recomended by NCRP
Thin sheets of AL are added over the xray machine
- With NCRP how much Al equivalent of total filtration should there be with less that 50 kVp?
50-70 kVp? over 70 kV[?
- 50 kVp 0.5 mm AL
50-70 kVp 1.5 mm Al
70 kVp 2.5 mm Al
- restricts the size and shape of xray beam
it is a metallic barrier made of lead
Reduces pt exposure bc increases mean nrg and improves image quality of reducig fog
- Types of collimation
- 1. round
- What type of collimation is recommended?
- As collimation restricts the size and shape of the beam (collimation decreases) what happens?
- No. photons decreases
Mean nrg unchanged
max nrg unchanged
- inverse square law
- relationship between distance and beam intensity
- what is intensity of beam at a given point inversely poroportional to?
- square of the distance from the focal spot
- what does increased film source distance do to beam intensity?
- reduces it
- What happens as distance of source film increases?
- no of photons decrease bc they are more spread out
mean nrg unchanged
max nrg unchanged
- The greater the source film distance, the ______ the beam intensity
- What must increase with increased distance?
- exposure time
- what decreases with increased source film distance
- decreased beam intensity and less radiation
- What things decrease radiation dose?
- less beam intensity
greater source film distance
increased source film distanc
- If distance is reduced to one half, beam intensity increases by how much?
- 4 times
- if distance is reduced 3 times, how much does beam intensity increase?
- 9 times
- if distance of source is doubled what happens to beam intensity ?
- decreases by four
- if a person standing 3 feet from an xray source receives 4 Rads of exposure how much would they receive at 6feet?
- 1 Rad
- what does an increase of 15 kVp require?
- half of exposure time
- what does the decrease of 15 kVp need?
- double exposure time
- A film is exposed at 10 mA for 12 sec. How much exposure time in sec. is required is mA is changed to 12?
- mA (old)+mA (new)
10 mA X 12 sec = 12 mA
- as xrays pass through the matter there is a gradual loss of energy and xrays graddually disappear
- gradual reduction in the intensity of xray beam is called what?
- How does attenuation occur?
- 1. photelectric absorbtion
2. comptom scatter
- What percent of photons pass through patients without interaction?
- 9%. this causes darker density or radiolucent areas on the radiograph after the film has been processed
- photoelectric absorption
- 30% of photons are absorbed this way on dental xray
Does not interact with film
So clear or white ares are seen-radioopaque
- describe steps of photoelectric absorption
- 1. xray photons is absorbed
2. incident photon with a little more energy than the binding energy of a K shell e- ejects e- from orbit. its is called photoelectron flies in space and is absorbed by another atom
4.L shell jusmps to K shell and gives off Characteristic radiation
- What does xray absorption depend on?
- photon nrg kVp
density of obj
atomic no of obj
- describe photon nrg
- higher kVp->hi energy photons->greater penetration less absorbtion
- what happens to absorbtion if you increase Z
- increase absorbance thats why lead is used for the collimater
- Xrays are deflected in all directions and contribute to unusful info to film
- What does scatter cause?
- Types of Scatter?
- 1.Coherent scatter
- coherent scatter
- lo nrg incident photon passes near outer shell e-. no loss of energy. direction of the incident xray photon is altered
- Compton scattering
- most common interaction between xray and body tissues
responsible for almost all scatter radiation
- moderate energy xrays strike outer shell e- or loosely bound e- causing it to eject from its orbit
- compton scatter
- what does compton scatter depend on?
angle of defelection
- if photons have a narrower angle of deflection, what happen?
- energy is retained and there is a bigger chance of reaching the film and producing fog
- e- density
- greater the no. of e-, higher the probabitiy of compton scatter.
- Where is compton scatter greatest?
- in bone bc hi Z
- how can compton scatter be minimized?
- rectangular collimation
shorter exposure time
- how are xrays produced?
- when hi speed e- decelerate or stop
Kinitic nrg becomes electromagnetic radiation
- Conditions necessary for xray production
- 1. gereration of e- by filamen
2. focus e-
3. produce hi speed e-
4. stop hi speed e- @ target
- source of e-
- cathode (tungston coil)
e- made by heating cathode
- Thermionic emission
- boiling of e- from filament by absorption of heat
- what does temp of filmant control?
- quantity of e- made
- how can temp be increased?
- increase mA or exposure time
- What does increaseing kVp do?
- cathode becomes more neg and anode becomes more pos. results in flow of hi speed e- toward the anode
- what happens to e- flow as potential difference increases/
- spped of e- increase
- when cathode e- stream strikes the anode target, 2 xrays occur. what are they?
- 1. general "bremsstrahlung radiation
2. characteristic radiation
- Bremsstrahlung radiation
- bulk of dental xray
cathode e- is deflected and deceleratted or stopped by nucleus of tungsten and kinitic nrg is lost as xray
- two mechanisms of bremsstrahlung radiation
- 1. direct hit of e- to nucleus
2. e- defelcted and decelerated by interaction with nucleus
- What type of energy does bremsstrahlung radiation have?
- heterogenous. energy and wavelength are not uniform
- what does energy of emitted xray photon resulting from deceleration of e- depend on?
- how close the e- pass to the nucleus
energy of e- (eV)
Charge of nucleus
- characeteristic radiation
- makes small porttion of xray
produces xray photon w/ energies specific for the target material
results in homogenours wavelength and energy
- process of characteristic radiaion
- incoming e- interact w/inner orbital e- of target atom
incident e- and k shell e- leave the target atom
Removal of an e- fro te target atom causes the atom to have an excess positive charge of energy
target atom becomes ionized
- how to get rid of excess charge in characteristic radiaiton
- e- drops from outer shell to inner shell causing release of nrg as xray. nrg is characteristic of target material and involved in orbital
- energy emitted by the shift of e- from one shell to another is equal to what in characteristic radiation?
- differnces in energy between two orbitals
- What happens when DC is applied to an xray generator?
- kilovoltage increaces
- what do all cathodes have same of/
- same energy and results in homogenous radiation in characteristic radiation
- advantage of using DC in xray machines
- xray photons with similiar energies lower no. of non diagnostic xrays allowing less radaion dose to pt
- why do we need to measure xrays?
- ionizing radaion harmful
know potentioal harmful effects
- device for measuring doses xradiation
- output of xray machine and radiation reaching living tissue
- absorbed dose
- measure of the energy absorbed by any type of ionizing radiation per unit massof any type of matter
SI is Gray
Absobed dose is typically used when indication harful effects
- equivalent dose
- comparison of biological effects produced by different ionizing radiations
- Unit of exposure
- R is defined as quantity of photons that make a defined no. of ion pairs in a cbic cm of air
SI unit is C/kg
- What is usedto compare bio effects of diff types of radiation on tissues
- equivalent dose
- personnel monitoring devices
- film badges
optically stimulates luminescene tech
- are of eruption of mandibular 1st premolar
- 10-12 yers
- height of contour of mandibular 1st premolar
- facial-cervical third 1/2 mm
lingula-middle third 1 mm
- what is facial surface of mandibular first premolare similiar to?
- predominant cusp on mandibular first premolar
- facial. it occludes
- describe facial cusp tip of mandibular first premolar
- cusp tip more rounded on premolar and is displaced medially
- most promininat ridge on mandibular first premolar
- central facial ridge
- proximal contacts of mandibular first premolar
- slightly cervical to junction of middle and occlusal thirds
- shape of mandibular first premolar
- shape of mandibular first premolar occulual table
- how do mesial marginal ridges and distal marginal ridgles run on mandibular first premolar?
- mesial ridge runs parralel to canine and distal amanginal rige run horizontal to canine
- no. of pits on mandibular first premolar
- 2 in central groove
- what is visible from looking at lingual side of mandibular first premolar?
- mesial and distal sufaces and large portion of occlusal surface is visible
- how is occlusal table placed on mandibular first premolar?
- occlusal tbale is tipped lingually
- difference in lingula and facial cusp of mandibular first premolar
- lingula cusp is shorter that facial
- describe mesial marginal ridge of mandibular first premolar
- mesial marginal ridge more nearly parallels the slope of the linulal ridge of the facial cusp
- difference in sides of mandibluar first premolara
- more curvature of cervial line on mesial than distal
- What seperates mesial lobe from lingual cusp on mandibular first premolar
- mesiolingual groove
- number of occlusal fossa on mandibular first premolar
- two occlusal fossa
- difference in mesial and distal proximal contacts on mandibular first premolar
- mesial side is flat and much narrower while distal is has a wide proximal contact
- only tooth with mesiolingual developmental groove
- first mandibular premolar
- does lingual cusp of mandibular first premolar occlude with max teeth?
- no only the facial cusp does
- age of eruption of mandibular second premolar
- 10-12 years
- height of contour of mandibular second premolar
- facial in cervial third 1/2mm
lingual-middle third 1 mm
- what erupts first, first or second premolar?
- difference in facial cusps tip between first and second mandibular premolars
- second facail cusp tiip is more rounded
- facial cusp of mandibular second premolar
- cusp tip reounded and displaced mesially
- proximal contacts of mandibular second premolars
- proximal contact in middle thrid
- shape of mandibuar second premolar rroot
- baenet shaped
- lingual view of mandibular second premolar
- no facail side visible and not much occlusal side visible
- what sepererates lingula cusp of mandibular second premolar?
- developmental groove
- larges lingual cusp on mandibular second premolar
- difference in mandibular first and second premolar proximal view
- on the first the occlusal suface slopes
onthe second the occlusal surface has two cusps like a V
- describe mesial and distal marginal ridges of mandibular second premolar
- mesial and distal marginal ridges more perpendicular to long axis of tooth. distal marginal ridge is at a lowere level occlusocervically
- three forms of second mandibular premolar
- Y H U
based on occlusal surface
- # of cusps of second mandibular premolar
- 2 or 3
- Y sencond mandibular premolar
- most common
lingulal dev groove runs on lingual surface
Y has central pit
facial/lingula width=mesiodisatl width
- U second mandibular premolar
- least commonit
converges linulaly transvers ridge with mesial and distal fossa
- H second mandibular premolar
- 2 cusps each are same size
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