Oral Radiology 2
Terms
undefined, object
copy deck
- 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
- Fluorescnece
- Instantaneous emission of light.
- Phosphors
-
Substance that causes fouorescence
Barium, platinocyanide
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?
- Vaccuum
- How did edmund kells die?
-
"BULLET TO THE BRAIN"
1928 - Howard Raper
-
1887-1979
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
dent-diagnosis
research
industrial users - 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
- 5
- 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
- Bitewing
- 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
- Radioopaque
-
white.
Example" amalgum stops radiation completely so it is radioopaque. so is bone - Radiolucent
-
Dark/ black
More density
Soft tissue in root canal - matter
-
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
- atom
- atom
-
smallest part of an element. cant be subdivided by ordinary chem means
can only be broken into subatomical particles by hi energy - nucleons
- protons and neutrons within the nucleus of an atom
- Radiation
- 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.
or
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
- ionization
- when a neutral atom acquires a charge
- what is required to overcome the electrostatic forces that bind the electrons to the nucleus
- energy
- what is a form of energy that forms a ion pair
- xrays
- two types of radiation
-
particulate
electromagnetic - 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
light waves
infrared
ultraviolet
xrays
gamma rays - 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
- wavelength
- distance between crests of two waves
- Wavelenght frequency correlation
-
when waveleght long, lo frequency, less penetration
when wavelenght is short, hi frequency, more penetration - frequency
- number of waves passing through a point per second
- What characterized hi energy photons?
- energy
- What characterizes lowere energy photons like radio waves
- wavelength
- 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
penetrates matter
no mass and no charge
travel in straight line
diverge from source
weightless
can be straight line
heterogenous energy
ionize gas
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?
- radioopaque
- periodontal lig radiolucent or opaque?
- lucent
- Describe Xray beam?
- heterogeneous and has certain quality and quantity
- What influences beam intensity?
-
exposure time
currenct mA
beam energy kVp
Source film distance
collimation
filtration - 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?
- 60/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?
- quantity
- what does kVp control/
- qUALITY
- 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?
- HVL
- 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?
- darkness
- Filtration
- 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
insulating oil
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 - Collimation
-
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
2. rectangular - What type of collimation is recommended?
- rectangular
- 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
- lesser
- 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
so sec=10 - Attenuation
- 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?
- attenuation
- 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
3.ionization occurs
4.L shell jusmps to K shell and gives off Characteristic radiation - What does xray absorption depend on?
-
photon nrg kVp
Structure thickness
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
- Scatter
- Xrays are deflected in all directions and contribute to unusful info to film
- What does scatter cause?
- FOG
- Types of Scatter?
-
1.Coherent scatter
2.compton 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?
-
energy
angle of defelection
e-density - 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
faster film - how are xrays produced?
-
when hi speed e- decelerate or stop
Kinitic nrg becomes electromagnetic radiation - 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
"genral" -
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 - dosimeter
- device for measuring doses xradiation
- exposure
- 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?
- canine
- 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
- diamond
- shape of mandibular first premolar occulual table
- trringle
- 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?
- first
- 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
- mesiolingual
- 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
Square outline
facial/lingula width=mesiodisatl width - U second mandibular premolar
-
least commonit
circular
converges linulaly transvers ridge with mesial and distal fossa - H second mandibular premolar
- 2 cusps each are same size