rando exam 2 stuff Flashcards
overexposed
excessive exposure
increased time, mA and kV
underexposed
time is main cause
and then excessive tube-receptor distance
Adjusts bright tones and brings more info to highlight of image
gain
Adjusts midtones of image by adjusting each pixel value in image
gamma correction
sensor bending and reversed placement
pPSPP only deals with
Damage to storage phosphors so there is no signal to area with damaged pixels
Scratch marks
sensor creasing
R vs. Coulombs/kg
exposure dose
-ionize air
RAD vs. Gray G
absorbed dose
REM vs Sievert Sv
equivalent dose
and
affective dose
radiation energy
onization from ionizing radiation exposure sets off multiple direct and indirect molecular reactions in :
Enzymatic repair or further deleterious molecular changes occur :
Deterministic and stochastic effects take place over time from :
less that second
min to hour
months to generations
fetal dose
0.02mGy
severity is proportional to dose
determinisitic
Both quick and take hours to decades to become evident
Both are result of ionization
direct and indirect
dose(amount) of radiation is correlated with
response or damage
Threshold must be reached before changes are observed
threshold non-linear curve
(dose response curves)
most biologic effects are
(linear or non linear)
non linear
no matter how small dose is, there is damage or risk
linear non-threshold curve
Time that elapses between exposure and appearance of clinical signs
May be short or long depending on
Total dose
Dose rate
latent periodo
Cell death
Changes in cell function
Breaking or clumping of chromo
Giant cell formation
Cessation of mitotic activity
Abnormal mitotic activity
period of innjury
Full recovery for a large percentage of individuals from a few weeks up to 2 years after exposure
*death likely at higher dose of >1.2 Gy
recovery period
young, immature, rapidly growing and dividing, least specialized cells
radiosens
mature, specialized cells
radioresistant
blood cells, small lymphocytes, bone marrow, reproductive cells
high sens to radiation and least radioresistant
connective tissue, breasts, salivary glands, growing bone and cartilage
intermediate sens to radiation
skin and thyroid gland
fairly low sens to radiation
t/f
Fractionation of total dose into multiple small doses provides greater tumor destruction than single large dose Also increases cellular repair of normal tissues
true
Studies show risk for congenital defects is negligible at
50mSv or less
for determinisitic risk for pregnancy, At absorbed dose of 0 to 50 mGy: there (is/is not) no risk of fetal death, malformation, growth, retardation or impairment of mental facility
is no
so well below deterministic risk
for stochastic risk estimate for pregnancy, an absorbed dose to the conceptus of ____ doubles the natural childhood cancer rate
25mGy
Reduce radiation exposure
Maintain high degree of dx efficiency
goals for oral and maxillofacial radiology
max collimation lead diameter
2.75 and rectangle shape preferred
Sensor speed (sens)
Lead (Pb) thyroid collar
Film-holding devices with beam alignment capability
Time-temperature or digital quality control processing
dose reduction mechs
Less operator exposure and better shield protection if the sensor DOES ____ the standing position of the operator
PARALLEL
