Ch 1 Flashcards
(18 cards)
Milliamperage seconds (number of electrons and number of x-rays) mA x time
mAs
Source to image receptor (as far back as possible)
SID
Object to IR distance
Always want object as close to IR as possible otherwise magnification distortion occurs (ex: shadow)
Want heart closer to IR
OID
Kilovoltage peak (penetrating ability of x-rays)
kVp
One thousandth of the unit to which it’s joined
Milli
1/1000 ampere (1000 mA = 1 A)
Milliampere
1/1000 second (1000 ms = 1 s)
Millisecond
1/1000 meter (1000 mm = 1 m)
Millimeter
An amount 1000 times the unit to which it’s joined
Kilo
1000 volts
Kilovolt
1000 grams
Kilogram
Intensity of the beam is “inversely” proportional to the “square of the distance”
Intensity of the beam decreases by 4 when the distance is doubled and is increased by 4 when the distance is halved
I1/I2=D2^2/D1^2
Inverse square law
Formula used when changing distances (SID)
Directly proportional
mAs1/mAs2=D1^2/D2^2
Exposure/density maintenance formula
Similar triangles formula
b/B=h/H
What does b in similar triangles formula represent?
Base of small triangle (object)
What does B in similar triangles formula represent?
Base of big triangle (IR)
What does h in similar triangles formula represent?
Height of small triangle (distance from object to source)
What does H in similar triangles formula represent?
Height of big triangle (SID)
