Radiation Protection in Pediatrics

Principles & ALARA - Tiny Patients, Big Care

• Pediatric tissues: ↑ radiosensitivity due to rapid cell division.
• Longer life expectancy: ↑ risk for stochastic effects (e.g., cancer) to manifest.
• Core Principles:
  • Justification: Benefit of exam outweighs radiation risk. Each exposure must be clinically indicated.
  • Optimisation: ALARA (As Low As Reasonably Achievable).
    • Use lowest possible radiation dose without compromising diagnostic quality.
    • Techniques: appropriate ↑kVp, ↓mAs, tight collimation, shielding (gonadal, thyroid).
• Diagnostic Reference Levels (DRLs) are crucial for pediatric dose optimisation.

⭐ Children have a 2-10 times higher risk of radiation-induced cancer compared to adults receiving an identical radiation dose for many tissues and cancer types.

Radiation Effects - Sensitive Sprouts

• Children: ↑ radiosensitivity due to:
  • Rapidly dividing cells.
  • Longer life expectancy for effects to manifest.
• Two main effect types:
  • Stochastic: No threshold, probability ↑ with dose (e.g., cancer, genetic mutations).
  • Deterministic: Threshold dose exists, severity ↑ with dose (e.g., skin erythema, cataracts, sterility).
• Highly sensitive tissues: Bone marrow, gonads, thyroid, lens, breast.

⭐ Children are estimated to be 2-10 times more sensitive to radiation-induced carcinogenesis than adults for the same dose, with specific risk varying by age and tissue type.

Dose Metrics & DRLs - Measuring Minimally

• Key Metrics:
  • Effective Dose (E): Overall risk (Sv). $E = \sum (H_T \times W_T)$.
  • CTDIvol: CT dose per slice (mGy). $CTDI_{vol} = \frac{CTDI_w}{Pitch}$.
  • DAP: Fluoro/X-ray dose (mGy.cm²).
  • SSDE: Size-adjusted CTDIvol (peds).
• Diagnostic Reference Levels (DRLs):
  • Advisory levels, not limits.
  • Typically 75th percentile of doses.
  • Aid high dose identification & protocol optimization.
  • Pediatric DRLs: age/weight specific.

⭐ DRLs are benchmarks for optimization, not strict limits. Consistently exceeding them warrants a review of imaging protocols and equipment performance.

Protection Techniques - Shielding Superstars

• Concept: Use attenuating materials (Lead/Pb-equivalents) to block radiation.
• Standard Thickness: 0.25 mm to 0.5 mm Pb-equivalent. Higher kVp may need thicker shields.
• Types & Application:
  • Gonad shields: Flat contact, shadow shields. Critical for all pediatric pelvic/hip X-rays.
  • Thyroid shields (collars): For neck, chest, spine imaging.
  • Eye shields/Lead glasses: Protect sensitive lens during head CT/fluoro.
  • Breast shields: Bismuth shields for CT; lead for general radiography.
• Placement: Directly on/close to patient, without obscuring anatomy of interest.

⭐ Gonadal shielding can reduce female gonad dose by up to 50% and male gonad dose by up to 95% if placed correctly.

Special Considerations - Guardians & Guides

• Guardians (Parents/Carers):
  • Presence encouraged for child comfort & cooperation.
  • Provided lead apron (min. 0.25-0.5 mm Pb).
  • Must not be pregnant.
  • Positioned to avoid direct beam.
  • Preferred for immobilization if needed.
• Staff (Guides):
  • Adhere to ALARA principle.
  • Use PPE (lead aprons, thyroid shields).
  • Maximize distance from source.
  • Minimize exposure time.
• Communication:
  • Explain procedure, benefits, risks to guardians.
  • Address concerns; obtain informed consent.

⭐ If a parent assists in immobilization, they must wear a lead apron & gloves, and avoid the primary beam.

High‑Yield Points - ⚡ Biggest Takeaways

• ALARA principle (As Low As Reasonably Achievable) guides all pediatric imaging.
• Children have ↑ radiosensitivity due to active cell division and longer lifespan.
• Justification (net benefit) and Optimization (lowest dose) are fundamental.
• Employ child-specific protocols and effective dose reduction techniques.
• Crucial: Shielding of gonads, thyroid, and breast tissue.
• Prioritize non-ionizing modalities (USG, MRI) whenever clinically suitable.
• Utilize Diagnostic Reference Levels (DRLs) for pediatric exams.