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

Protection