1. Technique Charts 📊
Standardized exposure factors for consistent image quality:
Variable kVp Chart
Fixed mAs, adjust kVp based on patient thickness
Rule: 2 kVp per cm of tissue change
Fixed kVp Chart
Fixed kVp, adjust mAs based on patient thickness
More common in modern practice
2. Radiographic Grids 📐
Absorb scatter radiation to improve image contrast:
Grid Ratio
Height of lead strips / Distance between strips. Common: 8:1, 10:1, 12:1
Grid Conversion Factors (Bucky Factor)
No grid: 1x | 5:1 grid: 2x | 8:1 grid: 4x | 12:1 grid: 5x | 16:1 grid: 6x
Grid Cutoff Errors
Off-level, off-center, off-focus, upside-down (focused grids)
3. Automatic Exposure Control (AEC) 🤖
How AEC Works
Ionization chambers detect radiation and terminate exposure when optimal density is reached.
Detector Selection
3 chambers: Left, Center, Right. Select based on anatomy of interest.
Density Controls (+/- adjustment)
Fine-tune exposure for patient variations. Each step = ~25% change.
4. Digital Radiography 💻
CR (Computed Radiography)
Phosphor plate → Reader → Digital image
Uses PSP (Photostimulable Phosphor)
DR (Direct Digital Radiography)
Flat panel detector → Immediate image
TFT arrays with scintillators or photoconductors
💡 Technical Tips
- ✓ Use grids when body part > 10 cm and kVp > 60
- ✓ Collimation reduces scatter = Better image quality + Less patient dose
- ✓ Digital systems have wider exposure latitude but don't overexpose!