1. Radiation Dose Limits ⚠️
Annual limits set by regulatory bodies (ICRP, NCRP):
Occupational (Radiation Workers)
- Whole body: 50 mSv/year (5 rem)
- Lens of eye: 150 mSv/year
- Extremities: 500 mSv/year
- Lifetime limit: Age × 10 mSv
Public (Non-Occupational)
- Whole body: 1 mSv/year (0.1 rem)
- Much stricter than occupational limits
Embryo/Fetus
- 0.5 mSv/month after declaration
- Most radiosensitive period: 8-15 weeks gestation
2. Personnel Monitoring Devices 📟
Film Badge
Traditional method. Monthly exchange. Permanent record.
TLD (Thermoluminescent Dosimeter)
Uses LiF crystals. More accurate. Reusable.
OSL (Optically Stimulated Luminescence)
Uses Al₂O₃ crystals. Can be re-read. Most sensitive.
Pocket Ionization Chamber
Real-time readings. Self-reading. Daily use.
3. Protective Equipment 🛡️
Lead Aprons
0.5 mm Pb equivalent. Covers trunk and reproductive organs. Reduces dose by 95%+.
Thyroid Shield
Protects radiosensitive thyroid gland. Essential for fluoro and CT.
Gonadal Shields
Flat contact or shadow shields. Protect reproductive organs when in primary beam.
Lead Glasses
Protect lens of eye during fluoroscopy and interventional procedures.
4. Biological Effects of Radiation 🧬
Deterministic (Non-stochastic)
- Threshold dose required
- Severity increases with dose
- Examples: Skin erythema, cataracts, sterility
Stochastic
- No threshold (any dose has risk)
- Probability increases with dose
- Examples: Cancer, genetic effects
💡 Protection Board Exam Tips
- ✓ 10-Day Rule / 28-Day Rule for pregnancy screening (LMP)
- ✓ Law of Bergonie and Tribondeau: Cells are more radiosensitive when rapidly dividing
- ✓ Most radiosensitive cells: Lymphocytes, Spermatogonia, Erythroblasts