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Radiology

Terms in this set (193)

Walkhoff
first dental radiograph
Roentgen
father of dental x-rays
Kells
paralleling technique
Raper
bitewings
Eastman Kodak
first dental film
Ionization
converting an atom into ions -electron removed form the atom causing an ion pair (atom is +, electron is -)
Beta particles
Fast electrons from nucleus
Cathode rays
High speed electrons that originate in an x-ray head
x-rays
No mass or weight (photons) / travel at speed of light /short wave length /produce a latent image
Secondary radiation (scatter radiation)
x-ray that has deflected from its path
Radiation exposure
C/kg or Roentgen - amount of ionization in a volume of air
Absorbed dose
Gy or rad -amount actually absorbed by tissues
1rem =
.01 Sv
1sv =
100 rems
MPD
Maximum Permissible Dose
Occupational people MPD
5 rem/year; 50 mSv/year; 0.05Sv/year
Pregnant Dental Personal MPD
0.5mSv per month while Pregnant
Nonoccupational People MPD
0.1 rem/year; 1mSv/Year
ALARA
As Low As Reasonably Achievable
Sensitivity to radiation High
small lymphocyte, reproductive, bone marrow
Sensitivity to radiation Fairly high
skin lens, oral mucosa
Sensitivity to radiation Low( Radioresistant)
mature bone muscle, nerve, thyroid and salivary gland
Most sensitive
small lymphocyte
Somatic
Not passed on
Acute
Large dose in short time
Chronic
Small amounts repeatedly over a long time
Children
Most susceptible to radiation damage
Mitotic
Cells that divide frequently - more sensitive to radiation
Cell metabolism
Cells that have a higher metabolism are more sensitive
Background radiation
Ranges from 15 to 30mrads
Risk of producing a fatal cancer
3 in 1 million
Skin damage 250rads in 14 days causes
erythema (redness)
Protection
federal and State legislation protects patients, operators, and general public
Lead apronThickness:
.3mm . Reduces exposure to reproductive cells to virtually 0
Pregnancy
okay to take films if needed
PID of choice
Rectangular (not used at USI to date) lots of room for error thus retakes are needed- However reduce radiation to patient if proper technique used to eliminate retakes. 16inch preferred! - less divergence of beam
Film Speed F
is best! 60% reduction in exposure
Film Speed D
not so good
Never keep film
in unit - causes fogging
Film Badge (pocket dosimeter)
Used to measure occupational exposure - worn at waist level
never wear Pocket Dosimeter
outside in sunlight; when you are the patient. Not required for dental professional in Indiana but is required in other states.
Never stand
in direct line of beam but a right angle, closer than 6 feet
Inherent Filtration
(includes oil, glass, and tubehead seal) - reduces low energy waves
.5 to 1.0mm
aluminum
Below 70kVp
1.5 mm aluminum filtration
Above 70kVp
2.5 aluminum filtration
Collimator
2.75 inches -reduces size of beam
Grade Changing from a C- to an A+ =
Electrons traveling from the (-) Cathode to the (+) Anode
The x-rays at the center of the resulting beam are known as the
central ray.
Cathode
supplies electrons
Anode
converts electrons into x-ray photons
Low voltage circuit
Regulates flow of electrical current to the filament
Milliamperage
7 to 15 mA for dentistry. Quantity or number of x-rays. Usually mixed with the seconds- mAs
Exposure time
Measured in impulses -60 impulses occur in 1 second
Kilovoltage
65 to 100 for dentistry. Kilovoltage peaks regulates the penetrating power
Quality of the x-ray
determines the contrast (shades of grey)
Low kVp =
short-scale contrast(black and white)
High kvp =
long scale contrast (grays)
Density
Overall Darkenss or blackness of the film
High contrast
Lots of blacks and whites (high contrast scale)
Low contrast
Many shades of gray (low contrast scale)
Source film distance =
target film distance (both terms mean same thing). determined by PID
longer the PID the less
distortion
Elongation
More vertical angulation needed
Foreshortening
Less vertical angualtion needed
Overlap
Correct the horizontal angulation
Black film
Exposed to white light
Clear film
Not exposed
Buccal Object/SLOB/Clark's Rule/localization technique
If you move the tubehead and the object moves the same way it's on the lingual - if you move the tubehead and the object moves the opposite way from where it is on the first film, it is on the buccal
Safelight
GBX2 - at least 4 ft away
If films left near the light to long they will appear
fogged
Manual dipping Average developing time at 65 degrees =
5 minutes
Developer
Elon / hydoquinone. Reacts with all silver halide crystals
Fixer
thiosulfite and alum (hardening agent). Removes unused silver halide crystals. "clears" the film
Panoramic Intensifying screens Rare earth screens
new and best (green light)
Panoramic Intensifying screens Old type
calcium tungstate (blue light)
Focal Trough also called
the image layer. Everything in this area can be seen pretty well. Horseshoe shaped
Incorrect patient position
turned to side
The side farthest from the film is ____ and the side closest to the film looks ____
magnified. smaller.
Too far forward
anterior teeth are narrow
Too far back
anterior teeth are wide (Fat Back...nobody wants a fat back!)
Arthrography
Imaging the soft tissues of the TMJ
Cephalometrics
Used by orthodontists for assessment
Transcranial
Most common film used for TMJ access
inverse square law
flashlight
divide by 4 if intensity lower
multiply by 4 if intensity increased
size 1 film
peds
size 2 film
normal
size 3 film
long
size 4 film
occlusal
bisecting technique
PA's
Bisecting angle technique
incipient decay
enamel only
frank decay
enamel and dentin
gross decay
multiple frank decay or bombed out decay
rampant decay
fast
pano indication
3rds, erruption patterns, pathology
fusion xray
dilaceration
concresence
accessory roots
hypercementosis
enamel pearl
panoramic anatomy
ionization
x-rays produce ____ when others do not
the ejection of an electron from an atom. produces charges ion pair or free radicals
what is ionization
ejection, electron, ion pairs, free radicals
ionization is the ____ of an ____ from an atom. produces charged ____ or ____
ion
an atom or molecule with a net electric charge due to the loss or gain of one or more electrons.
free radicals
an uncharged molecule (typically highly reactive and short-lived) having an unpaired valence electron.
AC electricity (alternating current)
movement of electrons (-) along a wire toward a (+) charge which changes direction 60 times per second
60
one second is how many impulses of x-rays
15
1/4 of a second is how many impulses of x-rays
amperes
describes the number (AMOUNT) of electrons flowing
voltage
describes the potential differences between the (-) and (+) and therefore, the speed of force of the moving electrons toward the (+) charge.
aluminum filtration
selectively takes out the weak (long wavelength)
milliamps (mA)
number of photons increase
photon
a particle representing a quantum of light or other electromagnetic radiation. A photon carries energy proportional to the radiation frequency but has zero rest mass.
exposure time
number of photons increase (quantity)
Kilovolt Peak (kVp)
Number of photons increase. Shorter wavelengths (more penetration). (Quantity and quality)
aluminum filtration
number of photons decrease. removed softer dangerous photons. hardens the beam. (quantity and quality)
distance (further away - need more x rays but NOT weaker)
number of photons decreases as beam spreads (quantity)
KVP & Aluminum Filtration
what only affected penetration quality
mA, exposure time, KVP,
density increases when what is increased
filtration and distance
density decreases when what is decreases
kip and alum filtration only
contrast is affected by what
mostly blacks and whites (high visual contrast) (easier to see caries)
a short scale of contrast looks like what
many shades of gray (low visual contrast)
long scale of contrast looks like what
less kVp and aluminum
short scale of contrast results from what
more kvp and aluminum
long scale of contrast restyle from what
penumbra
area of unsharpness
small focal spot, short object to film distance, large target to film distance, film and tooth parallel, beam perpendicular to film
principles of shadow casting
same lingual, opposite buccal
what is SLOB
in cathode
filament circuit is where
from cathode to anode
describe where the x rays travel
if closer to the beam, you're getting more radiation (duh)
inverse square law means what
2x the distance away = 2 squared
describe the inverse square law
radiolucent
the periodontal ligament is what
radiopaque
the lamina dura is what
u shaped
what shape is the zygomatic arch
internal
which one is lower? external or internal oblique ridge
sodium thiosulfate and ammonium thiosulfate
what is used to Harden film emulsion
velocity
what term describes the speed of a wave
anode
copper arm in the tube head
ma
what controls the temperature of the tungsten filament
elongation
insufficient vertical
too far anterior (anorexic)
panoramic erros: anterior teeth are skinny
too far posterior (pudgy)
panoramic errors: anterior teeth are blurred and wide
chin too high
condyles off side of panoramic means
chin too low
condyles off top of panoramic means
silver halide (bromide crystals on both sides of film)
Film emulsion consists of what
elon and hydroquinone
what in the developer turns only exposed crystals to metallic silver (black)
sodium thiosulfate
what in the fixer removed underdeveloped (including unexposed) cystrals
phosphorus plates
indirect radiography is what
hydrolysis, free radicals of water
most common mechanism of damage in humans from radiation
due to rapid cell mitosis associated with child's growth
why are children more sensitive to radiation
millisecond or years
latent period of radiation damage can be how long
reproductive tissue
what tissue has the highest sensitivity to radiation
nerve tissue
what tissue has the lowest sensitivity to radiation
reproductive tissues, lymphoid tissue, bone marrow, intestines, mucous membranes
what tissues have high sensitivity to radiation
nerve tissue, skeletal muscle, heart, optic lens, mature bone, mature cartilage
what tissues have low sensitivity
growing cartilage, growing bone, salivary glands, fine blood vessels, lungs, kidneys, liver
what tissues have medium sensitivity
examples: d-speed needs half as much exposure as c-speed
film speed: each alphabetical film group is TWO TIMES FASTER than the previous film group and needs HALF as much radiation
retangular collimation
reduces the area of patient's skin surface exposed by 50% to 65% over round
1.5
aluminum filtration must be how thick for up to and including 70 kvp
2.5mm
aluminum filtration must be how thick for over 70 kvp
long. beam doesn't spread as fast
less volume of tissue is irradiated if what cone is used
wall is mandatory is operator cannot stand at least 6 feet from the scatter source (measured from patients head). walls DO NOT necessarily require lead lining
barriers of radiation
formation of free radicals of water
the greatest cause of harmful human radiation effects in dental radiography involves
2.75 inches
for dental radiography, the maximum size of the radiation beam at the patient's face is no greater than
the maximum permissible dose for one week
an operator of x-ray equipment received 1 mSv of radiation for a period of one week. We could assume from this information that the operator had received
Roentgen
Maximum permissible dose exposure in air old units
coulomb/Kg
Maximum permissible dose exposure in air S.I. units
...
Maximum permissible dose exposure in air S.I. units
rad
Maximum permissible dose absorbed dose old units
Gray (Gr.)
Maximum permissible dose absorbed dose S.I. units
Rem (dosimetry)
maximum permissible dose dose equivalent in man old units
sievert (Sv) (dosimetry)
maximum permissible dose dose equivalent in man S.I. units
5 rem/year (5000mrem) x52 weeks
400 orem/mo. x4 week
100mrem/week
MPD occupational (old units)
MPD non-occupational 1/10 (applies to fetus of auxiliary)
0.5 rem/year (500mrem)
MPD occupational (new units)
0.05 sv./year (50msv.)
4mSv./mo
1mSv./wk
MPD non-occupational 1/10 (applies to fetus of auxiliary)
0.005Sv./year (5mSv)
long rectangular PID's
radiation protection can best be provided to the patient by using the following:
Roentgens
x-ray ionization in air is measure in
high penetrating rays of short wavelengths
which of the following statements most adequately describes the radiation produced by high kilo voltage?
60 times per second
alternating current travels in one direction and then reverses making a full cycles
true
the extra oral x-ray film is exposed primarily by light from the intensifying screens
true
excessive vertical angulation will cause an image which is shorter than the actual object
the maxillary process of the zygomatic arch
the pronounced U-shaped opacity typically seen in the maxillary posterior is likely
mylohyoid ridge
the internal oblique ridge turns into what
low visual contrast
long scale means what
high visual contrast
short scale means what
true
1% of X-rays are used - 99% are heat
Laminate dura
Radiopaque
PDL
radiolucent
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