OMFR Flashcards
(172 cards)
1
Q
What is the inverted Y made up of?
A
Maxillary sinus/floor of nasal cavity
2
Q
what is the isthmus of Y ?
A
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
3
Q
ANTRAL/ inverted Y =
A
floor of nasal fossa
4
Q
_________ = blurring at edge of structure on radiograph
A
Penumbra
5
Q
Protection from xrys = ____ feet away or barrier
A
6 feet , 90-135 degree
6
Q
Most of the E from xray is converted to
A
heat
7
Q
Fxn of oil in xray tube
A
cooling - dissipates the heat and cools of the anode
also copper dissapate het
8
Q
BEst type of xray beam?
A
short wavelength , HIGH E
9
Q
RAdiation exposre for dentist/year
A
50 mSv
10
Q
Purpose of collimnator
A
Reduces area of exposure AND volume of tissue exposed AND reduces low energy radiation AND reduces film fog, = block (lead) ; doesnt prevent fogging
11
Q
________ = electron emission from a heated metal (cathode). The cathode has its filament circuit that supplies it with necessary filament current to heat it up.
A
Thermionic emission
12
Q
Best E types to give the best x-ray:
A
short wavelength, high energy
13
Q
What is the primary source of radiation to the operator when taking x-rays?
A
Secondary radiation - from scatter from pt
14
Q
What is the max radiation dosage for a dental professional per year?
A
50msv/year or 5 rem/year
- per month = 4 msv, per week = 1 msv
15
Q
which is the digital detector in a digital immage?
A
Charge coupled device
16
Q
MRI uses what electromagnetic wave?
A
RADIOWAVES
17
Q
Collimation does everything except:
A
reduce average energy of x-rays
reduce pt exposure, reduce operator exposure, reduces film fog,
18
Q
Which material is used as a filter in X-ray machines?
A
aluminum
beam hardening - filters out low E photos yet inc mean beam e
19
Q
Collimation controls
A
size & shape of x-ray beam
collimation give the greatest decrease in radiation to the patient/gonads
20
Q
Elongation & foreshortening occurs when there is
A
excessive vertical angulation
Head/chin too up = reverse smile line
Head/chin downward = Exess SMILE
21
Q
the use of intensifying screens does what?
A
reduce the radiation
22
Q
X-ray with cone cut. What’s wrong?
A
MISALIGNED XRAY TUBE HEAD, incorrect beam centering
23
Q
Head/chin too up in pan =
A
reverse smile line - FROWN
the opposite of down gives you a frown
24
Q
Pano – max centrals look abnormally wide –position of pt head is
A
too far back
Head too far Back –> u will not see vertebrae on the side plus Max central are wide
25
X-ray tube target metal is made out of:
tungsten ( anode + )
```
(target = tungsten
filter = aluminum
collumnation = lead
Glass = insulation)
```
26
Exposure time for digital imaging is ____less than what is required for F speed film
50%
27
Head too far forward -->
you will see vertebra and incisors blurry and narrow
28
The area on the film that represents the image of a tooth is called the
umbra, or complete shadow
29
70% of the X ray energy produced is _______.
general radiation
30
elongation occurs with
decreased vertical angulation
31
foreshortening occurs
Foreshortening of roots caused by excess vertical angulation
32
If you take a PA and the tooth is foreshortened, why did it happen?
Vertical angulation was too large
33
X-rays filters are used for?
Reduced intensity of electron beam, selectively absorbs low energy photons
34
By what % do you decrease radiation when you use a square collimator vs. rectangular?
60%
35
F speed requires ____ of the exposure time of D - speed
60%
36
The area around the umbra is the
penumbra or partial shadow
37
The accurate adjustment of the line of sight of a telescope = _____
Collimation
38
_____ is a mechanism where the low quality, long wavelength xrays are absorbed from the exiting beam. Alumnium disks absorb lower penetrating xrays.”
“Filtration
39
PA distortion
14% ; 11-15%
40
Pano distortion is :
25% but could range 10-30%
41
_____ is the zone of unsharpness along the edge of the image; the larger it is, the less sharp the image will be.
penumbra
42
tear drop shaped in max sinus -
pterygomaxillary fissure
43
MRI uses what electromagnetic wave?
RADIOWAVES
44
Source/object distance for lateral ceph:
5 feet
45
Radiographic Picture: looked washed out, no contrast, what was adjusted?
• Increase kvp
46
light films =
(underexposed/image not dense enough):
[due to incorrect milliamperage]???
47
QUESTION: which electron level has the highest binding energy?
K
| K is located closest to the nucleus = highest energy
48
Which electron shell has highest power?
(f/d...outermost shell)
49
Nutrient canals seen radiographically most common where?
Mandibular incisors
50
In radiobiology, the "latent period" represents the period of time between
radiation exposure and onset of symptoms.
51
______= radiopacity under mandibular anteriors
Genial Tubricle
52
Which radiograph would you use to view a fracture of the in angle, body and ramus?
Lateral oblique
53
which anatomic strx comes up clear on radiograph and it looks like a fracture
intermaxillary suture
54
best view for zygomatic arches:
Pano ? CT?
| A submental vertex view affords excellent detail of the zygomatic arches.
55
Best imaging for sinusitis or sinus infection:
waters aka occipitomental
56
How do you prevent penumbra?
X-ray should be parallel (reduce object-film distance)
57
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
58
What structure can you not see on a PA radiograph?
Mandibular foramen (too posterior & inferior)
59
Dark films
dark = overexposed/image too dense.
| This is due to incorrect mA (too high), exposure (too long), incorrect kVp (too high).
60
________: has threshold, severity of effect is dose-related
Deterministic effects
61
_________: 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.
62
______ = ability for the beam to penetrate tissues, energy
Kvp:
63
calcified cauliflower appearnce at angle of mandible?
calcified lymphnodes
64
calcified stones superimposed over ramus
tonsiliths
65
calcification inline w/ angle of the mandible but at lvl of the hyoid bone
Atherscleroic plaque - calciffied carotid
66
8% of photon interactions ina an xray
Cohernet Scattering
67
Irradiation cause saliva to have lower -
sodium content
68
Radiation that is stochastic, with non-threshold effects what would a clinician notice first
leukemia
69
RadioRESISTANT tissues include:
muscle, nerves
70
Digital X-rays have _____ less exposure from d-films to digital films:
digital has 50% less radiation exposure
71
Bone marrow, reproductive cells, lymphoid cells, immature cells, intestine are al examples of _________ tissues
Radiosensitive
72
Radiation injury from?
free radical formation from indirect
73
_________ = 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)
74
Which type of radiation is constantly in effect?
Inhaled radon radiation
75
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
76
What is most radio-resistant cell:
Muscle
77
1-2 Gy exposure effects?
Pordromal ( anorexia, n/v fatigue)
onset = min to hours
78
What will cause xerostomia: chemo or radiation?
radiation
79
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
80
Radiation of 4(Gy) to the skin will cause?
Erythema
81
Which structure is most radio sensitive:
hemopoitic bone marrow
82
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
83
How does x-rays primarily damage cells?
Hydrolysis of water molecules
Indirect radiation chemistry
84
Increasing ImA alone results in a film with:
High contrast
If you increase distance, then you need to increase mA
85
KVp inc =
more penetrating, high energy
86
50 + Gy exposure effects?
Cardiovascular and CNS symptoms- lethergy, tremors, convulsions, ataxia, coma Death in 1-2 days
onset = death in 1-2 days
87
Primary source of xray photons is from ____
Bremstraughlung xray production
- e- strikes a target and brakes giving off E
- Generates CONTINUOUS SPECTRUM of E
88
T/F ok to do bone grafting in pt on fosamax?
FALSE. NO GRAFTING ; no ortho eitehr
89
How to provide tx to pt on bisphosphonates/ radiaiton
preextract questionable teeth, hyperbaric oxygen pre and post if doing invasive procedures
90
BAckground radiation = _____ and is mostly from _____
3.1 mSv
| radon
91
What is the mechanism of action of bisphosphonates?
Inhibit osteoclasts via apoptosis
dsnt add Ca to bone
92
_____ = 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
93
_____ collumnator is the best method to reduce radiation dose
Rectangular
cut radiation dose by 5
94
PID
postition idcating device
95
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)
96
The heated filament emits e- by
thermonic emission
97
_______ 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
98
Glass fxns as
insulation - and vaccum
99
Intensity refers to the
Quantity of e- ; # of photons ; gives densisty (darkness of image)
100
To get osteoradionecrosis, radiation dose must be:
Above 50 gys (above 60)
101
xrays are produced when : ≈
high speed e- hit the metal (tungsten) traget
102
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
103
Osteonecrosis is more common with IV drugs like
Zolmeda (zoledronic acid) and
aredia (palmidronate),
Suffix: -dronate
NOT Fosamax or boniva).
104
____ = how the xray beam weakens as it travesl thru matter
attenuation
105
Energy referes to
the QUALITY of e- and E of photons
| affects the contrast (difference among gray values)
106
Avg annual exposure to ppl living in US =
6.1mSv
3. 1 for background(radon)
3. 1 from manmade (medical imaging)
107
_____ 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
108
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)
109
xray are high freq high E waves b/w
UV and Gamma rays
| similar to visiable light waves
110
30% of photon interactions in xray
Photoelectric Absorption
incident phot connect forms ion pair
INC contrast
111
Tube current is measured in
Milliampers mA
affects intensity ; usually cant adjust
too much mA = too dark /overexposed
too littel mA = too noisy/underexposed
112
SID - source to image distance aka
FFD - focal film distance
target= focal=source
image = film
we want max SOD and min OID
113
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
```
114
____ accoutns for ~62% of photon interactions in an xray
COmption scattering
incident photon contact outer shell e- and forms an ion pair
DEC CONTRAST
115
1 Rotegen (1 C/kg) =
3.88 x 103 R = exposed dose = E produced by xray tube
116
too short exposure =
too noisey/underexposed
117
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
118
1 Grey - ____rads
100 = adsorbed dose
| -E absorbed in tissue
119
too long exposure =
too dark/overexposed
120
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
121
Film base =
flexible plastic
122
____ 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
123
fine grnaular or orange peel appearnce on xray
ground glass
124
Phleboliths (calcified bld clot) typically are seen
at the pterygoid plexus - sigmoid noth or pterygomaxillary fissure
125
Too low kVp =
too light,very high contrast;mostly photoelectric absorption
126
Film emulsion layer =
silver halide crystals in gelatin material
127
Cancer, Leukemia, Heritable Effects as a result of radiation refers to
Stochastic Effects
| Linear no-threshold model
128
too little mA =
too noisy/underexposed
129
_____ radiation chemistry accounts for 1/3 of bilogic effects
Direct
Indirect - 2/3
130
Film intensifying screen =
coated with flourescent phosphor to reduce amt of exposure needed
131
too high kVp =
too gray, not enough contrast,mostly Compton scattering
132
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
133
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
134
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
135
Digital senor CCD/CMOS comprised of
silicon sensore chip captures xray and rapidly displays image on monitor
136
_____ = shadow behind an image
Umbra
137
Fixer Soln
Ammonium thiosulfate ( cleanign agent, removes undvlp Ag halidecyrstals)
138
how often to record all errors
daily
139
Digital senor PSP comprised of
Barium flourhalide plates that capture and store xray E from dental exposure
140
______ = 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
141
how often to review error log
Weekly
142
too much mA =
too dark /overexposed
143
How often to examinf PSP plates for scratches, or inspect aprons for tears
MOnthly
144
Best film to visualize basilar skull or zygoma fx
Submentovertex view
| Base projection of skull
145
Central ray of xray beam aimed perpendicular to imaginary bisector b/w long axis of tooth and long axis of receptor
Bisecting angle Technique
146
Underexposed FILM image why?
dec exposure time
dec dvlpmnt time
old dvlper
of too cold ( low temp)
147
overexposed FILM image why?
INC exposure time
INC dvlpmnt time
Exposure to light
148
INC exposure Sec =
INC DENSITY
149
INC mA =
INC dentsity
150
INC kVP =
INC density ; DEC contrast
151
INC filter =
DEC density ; INC contrast
152
INC distance =
DEC density
source to film distance
153
HOw often shld maching be eval by health physicist, and verify digital sensors with phantom(person)
YEARLY
154
Herringbone or tire track on FILM what happend?
film placed backwards
155
CBCT most commonly used in
```
implant planning
( others = endo, ortho, TMJ ( hard tissues only)º
```
156
Best film of paranasal sinus
Waters 45
| angle PA ceph of skull
157
Best film to visualize condyle
towne's view 30º
| angle pa ceph of skull
158
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
```
159
most commong operative error in xray takin
elongation
160
xray beam and receptor not lined up properly ; ICp device and film holder
cone cut
161
Pan comes out with wavy lines
motion - pt moving during pan
162
classic target lesion seen on xray dx?
complex odontoma
163
___% mineral loss before showing up on xray
33
164
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
```
165
Thin long line radiopaqcity at angle of manible
calcified stylohoyid ligament
eagles syndrome
166
SLOB
Same lingual
Opposite Buccal
if beam moves right and object moves right = lingual
167
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)
168
___converts e- to photons
anode
169
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.
170
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)
171
Incorrect horizontal angulation of the x-ray tube head while making posterior molar bite wings will probably result in
overlapping of interproximals.
172
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
