⚙️Parameters
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Radiographic Technique Guide
The Exposure Triangle
- kVp (Kilovoltage Peak): Controls the penetrating power (quality) of the beam and image contrast. Higher kVp = lower contrast but better penetration.
- mAs (Milliampere-seconds): Controls the total amount (quantity) of radiation. Directly proportional to patient dose and image density/noise.
- SID (Source-to-Image Distance): Intensity follows the Inverse Square Law. Initializing exposure factors usually assumes standard SID (e.g., 100cm or 180cm).
The 15% Rule
A rule of thumb for adjusting contrast while maintaining density:
- Increase kVp by 15% → Halve the mAs (Same density, lower contrast/dose).
- Decrease kVp by 15% → Double the mAs (Same density, higher contrast/dose).
Body Habitus
Thickness changes require mAs adjustment. A general rule is to change mAs by a factor of 2 for every 4-5 cm change in thickness.
Grid Factor
Grids absorb scatter but require higher dose (Bucky Factor).
No Grid = 1x
8:1 Grid ≈ 3-4x mAs increase.
ALARA Principle
Always adhere to "As Low As Reasonably Achievable". Use the highest kVp compatible with diagnostic quality to minimize patient dose.