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60 terms

Intro to Radiography

radiography general questions
STUDY
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umbra
true border of object as imaged radiographically
Source-to-image distance (SID)
distance between focal spot and image receptor (IR)
scatter
radiation produced from xray photon interactions with matter where resulting photons continue in a different direction
central ray
theoretical center of a beam of radiation
distortion
misrepresentation of true size or shape of an object
contrast
visible difference between adjacent densities; controlled by kVp primarily
fog
unwanted exposure or film densities
half-value layer
amount of filtration needed to reduce the intensity of the beam by half
image receptor (IR)
medium to capture radiographic image
inverse square law
relationship between intensity and source of radiation
kilovoltage peak (kVp)
potential difference; controls penetrating ability; quality of photons produced by xray tube
latent image
invisible image created after exposure but before processing
millampere seconds (mAs)
controls quantity of photons produced by xray tube
positive beam limitation (PBL)
automatic collimation system used on diagnostic xray units
primary radiation
beam after it leaves xray tube & before it reacts with the patient
attenuation
reduction in energy by passing through matter
recorded detail
representation of an object's true borders
remnant radiation
radiation resulting after the xray beam exits the object
resolution
measurement of recorded detail on a radiograph
inverse square law
the intensity of a beam of radiation is inversely proportional to the square of its distance from the source
scatter radiation
nondiagnostic radiation that travels in different direction after interacting with the patients body
absorbed radiation
radiation that is absorbed by the patient tissues
anode
method to stop electrons; target; positive electrode of xray tube
cathode
source of electrons; filament; negative electrode of xray tube
voltage
method to accelerate electrons rapidly
photographic qualities
density and contrast
geometric qualities
recorded detail and distortion
distortion
misrepresentation of an object's true size or shape
density
degree of darkening; overall blackening of film emulsion; controlled by mAs
mAs reciprocity
any combination of mA x time producing equal mAs values should produce equal exposures and densities
Becquerel (Bq)
unit of radioactivity; 1 disintegration per second (dps)
Compton Scatter
higher energy photon knocks outer shell electron from orbit
most occupational scatter exposure is from:
compton scatter
bone densitometry
the use of DEXA scanning to evaluate for osteoporosis
DEXA
dual energy xray absorptometry
classic coherent scatter
lower energy photon interacts with atom; same energy released in different direction; no energy transferred to patient
photoelectric effect
high energy photon knocks out inner shell electron; complete absorption of energy
biggest risk from scatter radiation is from:
photoelectric effect
pair production
high energy photon interacts with nucleus; produces two elextrons at 180 degrees from each other
Type of scatter produced by PET scan
pair production
Sievert (Sv)
measure of dose equivalence and biological damage; absorbed dose x quality factor; 1 sv = 100 rem
Gray (Gy)
measure of absorbed dose; 1 Gy = 100 rads
Detent
when xray tube is aligned with the grid in the table
Energy level for classic coherent scatter
below 10 KeV
energy level required for pair production
1.02 MeV
energy level required for photodisintregation
10 MeV
old unit for Gray (gy)
rad. Radiation Absorbed Dose
old unit for Seivert (sv)
rem. Radiation Equivalent Man
prodromal stage
nausea vomiting diarrhea;
latent period
body feels fine; cell changes are occurring
manifest stage
organism feels full effect of radiation
bone marrow syndrome
exposure between 2-10 Gy (200-1000 rad); infection, hemorrhage, anemia
gastrointestinal syndrome
10-50 Gy (1000-5000 rad); Massive diarrhea, nausea, vomiting, fever
CNS Syndrome
above 50 Gy; convulsions, coma, death from increased intracranial pressure
somatic effects of radiation exposure
cataract formation; carcinogenesis
genetic effects of radiation exposure
recessive mutations in DNA apparent in future generations
Core Values of Human Rights Law
autonomy, dignity, equality, solidarity
assimilation
abandoning original culture/language and melting into larger group
biculturalism
being able to negotiate two separate cultures individually
Over 85
fastest growing segment of american population