PRIME FACTORS & EXPOSURE
What controls IR exposure?
mAs
Only _____% of target interactions produce x-ray photons.
1%
Which interaction results in greatest patient dose?
Photoelectric absorption
AEC directly controls which exposure factor?
mAs (time)
Brightness in digital imaging is controlled by
Auto-rescaling
What controls beam penetrability?
kVp
Which interaction dominates x-ray production in the tube?
Bremsstrahlung
Which process results in most occupational exposure?
Compton scatter
Which AEC chambers are used for PA chest exams?
The two outer chambers
Quantum mottle results from
Underexposure
Increasing kVp by ____% doubles IR exposure.
15%
Characteristic photons occur above what kVp level?
70 kVp
Name 2 interactions occurring at diagnostic energies.
Photoelectric and Compton
A grid is recommended when part thickness exceeds ____ cm.
10 cm
Define “dose creep.”
Trend toward intentional overexposure
Write the inverse square law equation.
I1/I2 = (D2/D1)²
List 4 requirements for x-ray production.
Vacuum, source of electrons, acceleration, sudden stop
Order from MOST → LEAST attenuating: tissues... air (4)
Bone → Muscle → Fat → Air
Define grid cutoff.
Excess absorption of primary beam by the grid
Digital image saturation occurs after ____ times overexposure.
4×
Name all prime exposure factors.
mAs, kVp, SID
Define attenuation.
Reduction in beam intensity as it passes through matter
What happens to the photon during photoelectric absorption?
It is completely absorbed
What effect does tight collimation have on IR exposure?
Decreases IR exposure
Which photons create the image?
Transmitted photons