study this Flashcards by Madyson mccullick

2 examples of inherent filtration

glass envelope
tube window
metal housing
immersion oil

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what occurs when you have a low kV

high gray scale

(high kV/voltage= low contrast= more shades of gray)
(low kV/voltage= high contrast= less shades of gray

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inverse square law, if distances is doubled from 8 to 16, what is the new intensity

1/4

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by using adjustment tools such as edge enhancer, you can stimulate illnesses and abnormalities to show that are actually not there

yes

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too much info on computer can cause

not function properly

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which of the following has most biological affect
direct or indirect

indirect 2/3
direct 1/3

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XR photons absorbed by H2O-> free radicals-> biological damage

indirect

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outcomes: repair, mutation, death
directly ionizes biological macromolecules

direct

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lethal dna damage
cell death
ex: xerostomia, acute radiation syndrome, erythema, fetal development
HAS threshold
severity is proportional to dose

deterministic (dose based)

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sublethal dna damage
gene mutation
replication of mutated cells
examples: leukemia, thryoid cancer
NO threshold
severity of effects DOES NOT depend on dose

stochastic (frequency)

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genetic mutations cause malignancy to what cells

somatic cells

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genetic mutations cause heritable effects to what cells

germ cells

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what factors modify effects of xradiation

decrease age (pediatric pts at risk)
increase dose rate
increase total dose
increase oxygen
cell type and function

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what stage of acute radiation syndrome is non lethal

prodromal period
<2 Gy

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what is the most lethal stage of acute radiation syndrome

CNS/CVS
>100 Gy

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what stage of acute radiation syndrome is lethal 2-8Gy?

what is supralethal >8Gy?

lethal: hemiatopietic
supralethal: Gastrointestinal

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what is the effect of radiation on
mucosa
teeth
salivary gland
bone
muscle

mucosa: mucositis, 2 degree infection
teeth: radiation caries and underdeveloped teeth
salivary gland: xerostomia
bone: osteoradionecrosis
muscle: fibrosis

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what kind of radiation causes radiation caries

indirect

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what are
occupational limits
non-occupation limits
pregnant limits

occupational limits: 5 rem or 50mSv
non-occupation limits: 0.5 rem or 5mSv
pregnant limits: 0.5 rem or 5 mSv (9 months)
.1rem or 1mSv (1 month)

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what kind of xrays do you take on pregnant patients

only take xrays during emergency circumstances

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examples of background radiation

radon
cosmic
terrestrial
internal

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what cancers have the highest risk for dental radiograph exposure

thryoid and leukemia

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where should you stand when taking xrays

6 feet away, behind barrier, 90-135 degree from beam

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primary reason for taking water’s skull xr

see the maxillary sinus

(chin is up)

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SLOB rule, move tube mesial and object also moves mesial

lingual

what comprises the inverted Y

nasal cavity floor and maxillary sinus

which of the following provides the best protection against radiation

thyroid collar

when tooth is not parallel to receptor, and beam is directed perpendicular to receptor

foreshortening

when tooth is not parallel to receptor and beam is perpendicular to tooth

elongation

if you shorten source to receptor what happens a. increases sharpness b. decreases magnification c. decreases sharpness d. increases magnification

c and d

what ionization has the most effect compton scattering photoelectric coherent

compton- most common 57-62%

-can ionize multiple -interacts with outer shell electron -xr photons continue in diff directions with less energy creating scatter until all energy lost

compton scatter ionization

-only ionizes -absorbed by inner shell electron -collides and loses energy

photoelectric

-excites but does not ionize -xr photon of low energy interact with outer orbital electron and change direction but no photoelectric produced

coherent

lady has colon cancer and thus had radiation. however, her 2 kids are at increased risk. this affected

germ cells

what is the most lethal part of hematopoetic syndrome

sepsis

the effect only seen in the person effected, NOT future generation generations

somatic

by federal law, a signal and light are required on every xray unit

true

how many Gy needed for treatment of solid tumors lymphomas intraoral cancer

solid tumors 60-80 Gy lymphomas 20-40 Gy intraoral cancer 50 Gy

operating kV listed below, what size of filtration do you need <50= 50 to 70= >70=

<50= 0.5mm 50 to 70= 1.5mm >70= 2.5mm

full time xray operator needs to have what on their person at all times

dosimeter personal monitor device

in x-radiation, absorbed dose is ______to equivalent dose

equal equivalent dose Ht= QF of 1 x absorbed dose Dt

in x-radiation, absorbed dose is _____ to the effective dose

less effective dose E= sum of absorbed dose Dt X Wt (tissue weighing factor)

what happens when you increase mA

increase density (and increase # of photons)

alpha particles have _____charge and a _____ LET than a proton

larger larger aplha +2 (high LET) beta +1 beta -1 neutron 0 electron -1 proton +1 xray NO CHARGE (low LET)

this reduces the amount of scatter radiation exposing film (and improves contrast)

grid (image inhancer)

radiograph sensor sizes

0= pediatric 1= anterior PA, pediatric BW 2= adult PA, adult BW, pedi occlusal 3= not used, longer BW 4= adult occlusal

what does rectifier do

converts AC to DC (convert alternative current to direct current) AND moves from cathode to anode

multiple line ruler picture that shows

quantitative image analysis

if you increase tube voltage, it will _____the x-ray quantity and _____the quality

increase increase

otto walkhoff

first dental radiograph

what occurs if images are compressed on computer and there is no space

decrease in storage

what does atomic number measure

protons

alpha particles have a ____LET, which means it has a ____mass and a ____velocity

higher LET higher mass lower velocity

what does tungsten target do

transform the kinetic energy of the colliding electrons into x-ray photons

what do you do to increase magnification

BAD, dont want this decrease source to object length or increase object to receptor length

what would increasing the sensor to object distance and decreasing the object to receptor distance do?

minimize magnification

what is the probability of occurence

stochastic (frequency)

what is the interaction of xray with matter called___radiation

ionizing

what is the indirect x-ray photons absorbed by to create free radicals

water

what are examples of threshold effects?

this is deterministic xerostomia erythema cataracts fetal development

as the oxygen content ____, it ____in the sensitivity

increases increases

what two things are important factors in radiosensitivity

younger age and increase of oxygen content increase total dose increase doe rate cell area exposed cell type and function

what is the max radiation dose of a pregnant dental hygienist

5mSv

what is it called when you do whatever you can to reduce the radiation dose

ALARA ALADA- as low as dx possible

if operating kV is equal to 70 and the aluminum filtration is 1.5mm, what needs to occur?

nothing needs to occur because kv of 50-70 is adequate with aluminum filtration size of 1.5mm kV <50 .5mm 50-70 1.5mm >70 2.5mm

what is the most effective way to reduce the dose

recessed x-ray tube a. xray tube head (mandated) b. filtration (aluminum filter) c. collimation (lead)

another question about effective way to reduce something

speed of sensor (want quicker)

where do you want to place the bacscatter shield at

at the end of the PID(closest to patient)

what do you do with new patient that has a lot of things done to them. what dental radiographs do you use?

full mouth series

what occlusal radiographs do we use

PSPP

cross sectional has ____ posterior coverage and ___angle

more coverage less angle

what occlusal radiographs do we use

film and PSPP

secondary photons resulting in image degradation when doing extraoral imaging

what is the point of waters radiograph

see the maxillary sinus

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