OMFR Flashcards
What is the inverted Y made up of?
Maxillary sinus/floor of nasal cavity
what is the isthmus of Y ?
Isthmus of Y = where nasal floor (straight radiopaque line) and maxillary sinus (curved radiopaque line) start and meet). What are the two anatomical factors that border this? Floor of nasal cavity and maxillary sinus
ANTRAL/ inverted Y =
floor of nasal fossa
_________ = blurring at edge of structure on radiograph
Penumbra
Protection from xrys = ____ feet away or barrier
6 feet , 90-135 degree
Most of the E from xray is converted to
heat
Fxn of oil in xray tube
cooling - dissipates the heat and cools of the anode
also copper dissapate het
BEst type of xray beam?
short wavelength , HIGH E
RAdiation exposre for dentist/year
50 mSv
Purpose of collimnator
Reduces area of exposure AND volume of tissue exposed AND reduces low energy radiation AND reduces film fog, = block (lead) ; doesnt prevent fogging
________ = electron emission from a heated metal (cathode). The cathode has its filament circuit that supplies it with necessary filament current to heat it up.
Thermionic emission
Best E types to give the best x-ray:
short wavelength, high energy
What is the primary source of radiation to the operator when taking x-rays?
Secondary radiation - from scatter from pt
What is the max radiation dosage for a dental professional per year?
50msv/year or 5 rem/year
- per month = 4 msv, per week = 1 msv
which is the digital detector in a digital immage?
Charge coupled device
MRI uses what electromagnetic wave?
RADIOWAVES
Collimation does everything except:
reduce average energy of x-rays
reduce pt exposure, reduce operator exposure, reduces film fog,
Which material is used as a filter in X-ray machines?
aluminum
beam hardening - filters out low E photos yet inc mean beam e
Collimation controls
size & shape of x-ray beam
collimation give the greatest decrease in radiation to the patient/gonads
Elongation & foreshortening occurs when there is
excessive vertical angulation
Head/chin too up = reverse smile line
Head/chin downward = Exess SMILE
the use of intensifying screens does what?
reduce the radiation
X-ray with cone cut. What’s wrong?
MISALIGNED XRAY TUBE HEAD, incorrect beam centering
Head/chin too up in pan =
reverse smile line - FROWN
the opposite of down gives you a frown
Pano – max centrals look abnormally wide –position of pt head is
too far back
Head too far Back –> u will not see vertebrae on the side plus Max central are wide
X-ray tube target metal is made out of:
tungsten ( anode + )
(target = tungsten filter = aluminum collumnation = lead Glass = insulation)
Exposure time for digital imaging is ____less than what is required for F speed film
50%
Head too far forward –>
you will see vertebra and incisors blurry and narrow
The area on the film that represents the image of a tooth is called the
umbra, or complete shadow
70% of the X ray energy produced is _______.
general radiation
elongation occurs with
decreased vertical angulation
foreshortening occurs
Foreshortening of roots caused by excess vertical angulation
If you take a PA and the tooth is foreshortened, why did it happen?
Vertical angulation was too large
X-rays filters are used for?
Reduced intensity of electron beam, selectively absorbs low energy photons
By what % do you decrease radiation when you use a square collimator vs. rectangular?
60%
F speed requires ____ of the exposure time of D - speed
60%
The area around the umbra is the
penumbra or partial shadow
The accurate adjustment of the line of sight of a telescope = _____
Collimation
_____ is a mechanism where the low quality, long wavelength xrays are absorbed from the exiting beam. Alumnium disks absorb lower penetrating xrays.”
“Filtration
PA distortion
14% ; 11-15%
Pano distortion is :
25% but could range 10-30%
_____ is the zone of unsharpness along the edge of the image; the larger it is, the less sharp the image will be.
penumbra
tear drop shaped in max sinus -
pterygomaxillary fissure
MRI uses what electromagnetic wave?
RADIOWAVES
Source/object distance for lateral ceph:
5 feet
Radiographic Picture: looked washed out, no contrast, what was adjusted?
• Increase kvp
light films =
(underexposed/image not dense enough):
[due to incorrect milliamperage]???
QUESTION: which electron level has the highest binding energy?
K
K is located closest to the nucleus = highest energy
Which electron shell has highest power?
(f/d…outermost shell)
Nutrient canals seen radiographically most common where?
Mandibular incisors
In radiobiology, the “latent period” represents the period of time between
radiation exposure and onset of symptoms.
______= radiopacity under mandibular anteriors
Genial Tubricle
Which radiograph would you use to view a fracture of the in angle, body and ramus?
Lateral oblique
which anatomic strx comes up clear on radiograph and it looks like a fracture
intermaxillary suture
best view for zygomatic arches:
Pano ? CT?
A submental vertex view affords excellent detail of the zygomatic arches.
Best imaging for sinusitis or sinus infection:
waters aka occipitomental
How do you prevent penumbra?
X-ray should be parallel (reduce object-film distance)
Which radiograph would you use to view a fracture of the mandibular symphisis?
Posterio-Anterior also Mand occlusal works too.
Lateral oblique for fractures in angle, body and ramus
What structure can you not see on a PA radiograph?
Mandibular foramen (too posterior & inferior)
Dark films
dark = overexposed/image too dense.
This is due to incorrect mA (too high), exposure (too long), incorrect kVp (too high).
________: has threshold, severity of effect is dose-related
Deterministic effects
_________: no threshold & not dose-related, probability of effect /likelihood that something will happen
Stochastic effects
- Stochastic effects are assoc w/ long-term, low-level (chronic) exposure to radiation. Increased levels of exposure make these health effects more likely to occur, but do not influence the type or severity of the effect.
______ = ability for the beam to penetrate tissues, energy
Kvp:
calcified cauliflower appearnce at angle of mandible?
calcified lymphnodes
calcified stones superimposed over ramus
tonsiliths
calcification inline w/ angle of the mandible but at lvl of the hyoid bone
Atherscleroic plaque - calciffied carotid
8% of photon interactions ina an xray
Cohernet Scattering
Irradiation cause saliva to have lower -
sodium content
Radiation that is stochastic, with non-threshold effects what would a clinician notice first
leukemia
RadioRESISTANT tissues include:
muscle, nerves
Digital X-rays have _____ less exposure from d-films to digital films:
digital has 50% less radiation exposure
Bone marrow, reproductive cells, lymphoid cells, immature cells, intestine are al examples of _________ tissues
Radiosensitive
Radiation injury from?
free radical formation from indirect
_________ = electrons are emitted from matter (metals and non-metallic solids, liquids or gases) as a consequence of their absorption of energy from electromagnetic radiation of very short wavelength and high frequency, such as UV radiation.
photoelectric effect (how x-rays interact w/ matter)
Which type of radiation is constantly in effect?
Inhaled radon radiation
2-7 Gy exposure effects?
Hematopoietic symptoms -infxn, hemorrhage, anemia
onset = day to months
Probability of Death low: 10-30 days after exposure; if left untreated
What is most radio-resistant cell:
Muscle
1-2 Gy exposure effects?
Pordromal ( anorexia, n/v fatigue)
onset = min to hours
What will cause xerostomia: chemo or radiation?
radiation
Sharper images, Less magnification, and X rays less divergent occurs when source is
far from obj
LONG source to object distance
also wiht SHORT object to receptor distance
Radiation of 4(Gy) to the skin will cause?
Erythema
Which structure is most radio sensitive:
hemopoitic bone marrow
7-15 Gy exposure effects?
Gastrointestinal symptoms
-n/v, prolonged diarrhea, electrolyte imbalance, circulatory collapse.Hematopoietic symptoms also noted
onset = weeks to months
Death: 3-10 days
How does x-rays primarily damage cells?
Hydrolysis of water molecules
Indirect radiation chemistry
Increasing ImA alone results in a film with:
High contrast
If you increase distance, then you need to increase mA
KVp inc =
more penetrating, high energy
50 + Gy exposure effects?
Cardiovascular and CNS symptoms- lethergy, tremors, convulsions, ataxia, coma Death in 1-2 days
onset = death in 1-2 days
Primary source of xray photons is from ____
Bremstraughlung xray production
- e- strikes a target and brakes giving off E
- Generates CONTINUOUS SPECTRUM of E
T/F ok to do bone grafting in pt on fosamax?
FALSE. NO GRAFTING ; no ortho eitehr
How to provide tx to pt on bisphosphonates/ radiaiton
preextract questionable teeth, hyperbaric oxygen pre and post if doing invasive procedures
BAckground radiation = _____ and is mostly from _____
3.1 mSv
radon
What is the mechanism of action of bisphosphonates?
Inhibit osteoclasts via apoptosis
dsnt add Ca to bone
_____ = further from source, less photons per unit area
Inverse square law
intensity * (1/ (distance^2) )
intensity is inversely proportional to square of the distance from the source
peroration shld be 6ft away from source
_____ collumnator is the best method to reduce radiation dose
Rectangular
cut radiation dose by 5
PID
postition idcating device
Pt has stage 1 osteonecrosis from bisphosphonate. What do you do?
debride area or rinse with chlorhexidine
- If STAGE 1 (exposed bone/asymptomatic) - rinse Chlorhexidine - conservative tx
- If STAGE 2( expose bone/pain/soft tissue rxn-swelling/infxn - Refer to OS or do under Hyperbaric O2
Stage 3 (path fx, fistula, osteolysis on xray)
The heated filament emits e- by
thermonic emission
_______ is the secondary source of xray photons
Characteristic xray production
- E- accidentally knocks into another. e- drops into lower E orbital ( usally the K shell)
- Emits a photon of SPECIFIC E
Glass fxns as
insulation - and vaccum
Intensity refers to the
Quantity of e- ; # of photons ; gives densisty (darkness of image)
To get osteoradionecrosis, radiation dose must be:
Above 50 gys (above 60)
xrays are produced when : ≈
high speed e- hit the metal (tungsten) traget
the copper rod located in the xray head is used to
dissapate the heat and a leaded glass envelope surrounds and isulates the entire assembly
Osteonecrosis is more common with IV drugs like
Zolmeda (zoledronic acid) and
aredia (palmidronate),
Suffix: -dronate
NOT Fosamax or boniva).
____ = how the xray beam weakens as it travesl thru matter
attenuation
Energy referes to
the QUALITY of e- and E of photons
affects the contrast (difference among gray values)
Avg annual exposure to ppl living in US =
6.1mSv
- 1 for background(radon)
- 1 from manmade (medical imaging)
_____ refers to movement of E as a combination of electrical and magnectic fields
Electromagnectic RAdiation ( type of ionizing rad)
Shorter wavelength = higher E
Gamma> xray>UV> violet to red>infrared>microwave>radiowave
Dose reduction things to do
ALARA or ALADA
- use E/F speed films or digital
- use >18cm soure-to-obj distance to reduce exposure and inc image clarity
- Use rectangular collum ( BEST WAY)
xray are high freq high E waves b/w
UV and Gamma rays
similar to visiable light waves
30% of photon interactions in xray
Photoelectric Absorption
incident phot connect forms ion pair
INC contrast
Tube current is measured in
Milliampers mA
affects intensity ; usually cant adjust
too much mA = too dark /overexposed
too littel mA = too noisy/underexposed
SID - source to image distance aka
FFD - focal film distance
target= focal=source
image = film
we want max SOD and min OID
xray setting most frequently changed
Exposure time (sec) Exposure time affects intensity ( density) too long = too dark/overexposed too short = too noisey/underexposed dec when digital sensors used or small child
____ accoutns for ~62% of photon interactions in an xray
COmption scattering
incident photon contact outer shell e- and forms an ion pair
DEC CONTRAST
1 Rotegen (1 C/kg) =
3.88 x 103 R = exposed dose = E produced by xray tube
too short exposure =
too noisey/underexposed
1 sievert = ____ rem
100
= Energy abs in tissue multiplied by radiation weighing factor
-Equivalent dose
-Effective dose = Energy abs in tissue multiplied by tissue weighing factor
1 Grey - ____rads
100 = adsorbed dose
-E absorbed in tissue
too long exposure =
too dark/overexposed
Hair loss, cataraact,skin damage, oral mucositis as a result of radiation refers to
Deterministic Effects
Must be greater than the threshold dose to see effects
0.1Gy in-utero defect 0.3 cataract 3 = radioatin burns
Film base =
flexible plastic
____ refers to atomic nuclei or subatomic particles moving at high velocity
Particulate Radiation (2nd type of ionizing rad)
alpha and beta praticle from radioactive decay are examples
fine grnaular or orange peel appearnce on xray
ground glass
Phleboliths (calcified bld clot) typically are seen
at the pterygoid plexus - sigmoid noth or pterygomaxillary fissure
Too low kVp =
too light,very high contrast;mostly photoelectric absorption
Film emulsion layer =
silver halide crystals in gelatin material
Cancer, Leukemia, Heritable Effects as a result of radiation refers to
Stochastic Effects
Linear no-threshold model
too little mA =
too noisy/underexposed
_____ radiation chemistry accounts for 1/3 of bilogic effects
Direct
Indirect - 2/3
Film intensifying screen =
coated with flourescent phosphor to reduce amt of exposure needed
too high kVp =
too gray, not enough contrast,mostly Compton scattering
FAster teh film the less _____ needed
exposure
A>B>C>D>E>F
larger crystal, Double emulsion, radiosenstive dye added to emulsion = all make FASTER film
Dveloper soln
Phenidone (Ag ion to metallic Ag) AND Hydroquinone (reduce phenidone to original)
dvlpr converts crystal to metallic silver grains that are seen as dark on xray - is what convert invisble to visible
if image too light - dvlpr needs changed
Tube Potential is measured in
kVp
affect intensity AND energy
too high = too gray, not enough contrast,mostly Compton scattering
Too low = too light,very high contrast;mostly photoelectric absorption
Digital senor CCD/CMOS comprised of
silicon sensore chip captures xray and rapidly displays image on monitor
_____ = shadow behind an image
Umbra
Fixer Soln
Ammonium thiosulfate ( cleanign agent, removes undvlp Ag halidecyrstals)
how often to record all errors
daily
Digital senor PSP comprised of
Barium flourhalide plates that capture and store xray E from dental exposure
______ = side shadow, fuzzy
Penumbra
Penumbra size depends of Focal spot size (FSS) ; SOD; OID
we want lil -no penumbra
the smaller the FSS (beam) = smaller penumbra = better/sharper image
( FSS *OID )/SOD
how often to review error log
Weekly
too much mA =
too dark /overexposed
How often to examinf PSP plates for scratches, or inspect aprons for tears
MOnthly
Best film to visualize basilar skull or zygoma fx
Submentovertex view
Base projection of skull
Central ray of xray beam aimed perpendicular to imaginary bisector b/w long axis of tooth and long axis of receptor
Bisecting angle Technique
Underexposed FILM image why?
dec exposure time
dec dvlpmnt time
old dvlper
of too cold ( low temp)
overexposed FILM image why?
INC exposure time
INC dvlpmnt time
Exposure to light
INC exposure Sec =
INC DENSITY
INC mA =
INC dentsity
INC kVP =
INC density ; DEC contrast
INC filter =
DEC density ; INC contrast
INC distance =
DEC density
source to film distance
HOw often shld maching be eval by health physicist, and verify digital sensors with phantom(person)
YEARLY
Herringbone or tire track on FILM what happend?
film placed backwards
CBCT most commonly used in
implant planning ( others = endo, ortho, TMJ ( hard tissues only)º
Best film of paranasal sinus
Waters 45
angle PA ceph of skull
Best film to visualize condyle
towne’s view 30º
angle pa ceph of skull
Central ray of xray beam aimed perpendicular to long axis of tooth and receptor
Parallelling Technique OID inc ( vs bisecting tech) imagge will be magnified
most commong operative error in xray takin
elongation
xray beam and receptor not lined up properly ; ICp device and film holder
cone cut
Pan comes out with wavy lines
motion - pt moving during pan
classic target lesion seen on xray dx?
complex odontoma
___% mineral loss before showing up on xray
33
maligant lesion typicallly show what characteristics?
ill-defined ( ragged/moth-eaten) irregular border radiolucent ramus or post mand Erosive, destructive Invasive,destructive, paraesthesia floating teeth spiked roots asym widening of PDL and loss of lamina dure
Thin long line radiopaqcity at angle of manible
calcified stylohoyid ligament
eagles syndrome
SLOB
Same lingual
Opposite Buccal
if beam moves right and object moves right = lingual
thin flat ovoid superimposed over mand anterior
sialolith in submand duct ( thin flat oval) ; sialolith in gland more round (in body of ramus mid IAN canal)
___converts e- to photons
anode
what is measured by the half-value layer?
Filtration
The half-value layer is the thickness of a material (usually aluminum) that decreases the intensity of the x-ray beam by half.
The higher the half-value layer, the thicker the piece of aluminum needed to block the x-ray beam.A quarter-value layer is the amount of a material that reduces the beam intensity to one-fourth of the value obtained without any test filters.
Fixing solution interacts with silver in what way?
It removes undeveloped silver salts.
Includes:
Clearing agent: Removes undeveloped silver halide crystals (ammonium thiosulfate)
Tanning agent: Hardens and preserves the emulsion (aluminum salts)
Activator: Maintains the fixer’s level of acidity and also neutralizes the developer (acetic acid)
Preservative: Prolongs shelf life of the solution (sodium sulfite)
Solvent: Dissolves the other substance and ingredients (water)
Incorrect horizontal angulation of the x-ray tube head while making posterior molar bite wings will probably result in
overlapping of interproximals.
Filtration is used in dental x-ray machines to remove
A- Scatter radiation photons
B- High energy electrons
C- Long wavelength photons
D- Low energy electrons
C
Long wavelength = lower energy
PHOTONS NOT ELECTRONS
