1. RAD 354 Chap. 13 Radiographic Technique
Four PRIMARY exposure factors:
kVp mA
Time
distance

2. In the next 5 minutes
Write down “bullets” about what happens when on RAISES kVp

3. Memory “jerk” for grids
Write the following:
5 2
8 4
12 5
16 6

4. Now What???
5:1 = 2X mAs
8:1 = 4 X mAs
12:1 = 5 X mAs
16:1 = 6 X mAs

5. kVp Beam Qualtiy Penatration Beam intensity HVL
Primarily responsible for quality, BUT INCREASES in kVp also make x-ray production SLIGHT more productive
Penatration
Beam intensity
HVL
Biggest exposure factor affecting CONTRAST

6. mA
DIRECTLY responsible for AMOUNT of radiation produced (Quantity). As mAs is doubled, so is the number of photons produced and so is PATIENT DOSE
mA stations are responsible for focal spot size selection

7. Time
Exposure times should be practical and short enough to stop patient motion, but the shortest times also result in the most radiation output per unit of time – thus MORE wear and tear on the x-ray tube
mAs = time X mA
mAs is only measured by tube current
Responsible for Optical Density (OD)

8. Distance (SID)
The most “forgotten” exposure factor, but perhaps the most important
Inverse Square Law
Primarily effects Optical Density (OD)
NO effect on quality
Other distance related terms:
FFD, FOD, OFD, FRD, ORD, SSD
Other geometric factors (F.S. size, pt. size, part orientation to CR and receptor

9. Filtration kVp driven Inherent (.5 mm al equiv)
Added (2.0 which may also include some filtration from localizer light apparatus, etc.) in a kVp unit
Total filtration : inherent + added (2.5 mm al equivalent)

10. Generators
Half wave (120 cycles/sec = 60 impulses per second) – 100% ripple
“self rectified” is also half wave where the X-RAY TUBE is the DIODE
Full wave rectification (120 cycles per second = 120 impulses per second) – 1--% ripple
3 phase, 6 pulse = 14% ripple (33% more radiation per exposure over full wave)
3phase, 12 pulse = 4% ripple (40% more per exposure over full wave
Hi frequency = <1% ripple