Radiation Units & Quantities (CTBC 21) Flashcards
2 means of measuring x-rays
Radiation in Air
Radiation in Tissue
Exposure
Number of ionizations created in air
Units of Exposure
Coulombs per kilogram (C/kg)
6.242x10^18 ionizations equals
1 coulomb
Traditional units of radiation measurement
Roentgens (R)
(more common in practice)
2.58 x 10^-4 C/kg
1 Roentgen
Typically the exposure in air created by CT is significantly less than…
1C/kg or 1R
(1 C/kg ~ 3876 R)
(air) KERMA
Kinetic Energy Released per unit MAss
(Alternative to measuring exposure)
Air kerma quantifies radiation by measuring
Energy of ionizations
Ionizations
Liberated electrons
Air kerma measures _____ of ionizations; Exposure measures _______ of ionizations
energy
number
Air Kerma Units
Gy
mGy
Both _______ and _______ can be used to measure radiation produced by CT x-ray tube, scatter radiation produced during CT procedure, scatter radiation escaping CT scan room
Exposure
Air kerma
Measuring the radiation produced by a CT x-ray tube is readily done with
Exposure or Air Kerma
Measuring the scatter radiation produced during a CT procedure is readily achieved using
Exposure or Air Kerma
Measuring the scatter radiation escaping the CT scan room is readily achieved using
Exposure or Air Kerma
Increasing mA _______exposure and air kerma
Increases
Increasing kVp _______ exposure and air kerma
Increases