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Chapter 38: Occupational Radiation Dose Management

Objectives

• Understand units and concepts of occupational radiation exposure.

• Discuss methods for reducing exposure.

• Explain positioning of occupational radiation monitors.

• Discuss personnel radiation monitoring reports.

• List available thicknesses of protective apparel.

Occupational Radiation Exposure

• Exposure Categories:

  • Average whole-body dose: 0.7 mSv/yr.

  • 53% receive less than minimum detectable dose.

  • 88% receive <1 mSv/yr.

  • 0.05% receive >50 mSv/yr.

• Radiation Dose Measurement:

  • Measured in Gyt (rads) for dose, Gya (roentgens) for exposure.

  • Rem for radiologic technologists and radiologists' exposure.

  • Effective dose (Sv) for radiation protection.

• Occupational Exposure Limits:

  • Recommended dose limit: 0.5 Sv/yr (5000 mrem/yr).

  • For general x-ray activity: max 1 mSv/yr (100 mrem/yr).

Fluoroscopy

• Highest exposure during fluoroscopy.

• Relation of personnel exposure to x-ray beam-on time.

• Mobile Radiography:

  • Use of protective aprons and exposure cords to maintain distance.

Dose Rate and Exposure Calculations

• Formula: Exposure = Exposure rate × Time.

• Example:

  • 2.5 Gya/hr × 2.5 minutes = 0.1 mGya.

Interventional Radiology

• Higher exposure due to longer beam-on times.

• Importance of extremity monitoring.

Mammography

• Low personnel exposure due to low kVp, resulting in less scatter.

• Use of barriers in dedicated mammography units.

Computed Tomography (CT)

• Low exposure levels, mainly secondary radiation.

• Monitoring procedures required during imaging.

Surgery and Mobile Radiology

• Minimal occupational exposure among surgical staff.

• PPE and monitoring are crucial in mobile radiography settings.

Radiation Dose Limits

• Whole-body dose limits established by NCRP.

• MPD concept replaced by annual cumulative dose limits.

• Recent recommendations address specific organ exposures.

Protective Apparel

• Must be worn during fluoroscopy and mobile radiography.

• Different thicknesses: 0.25, 0.5, and 1 mm of lead equivalent.

• Maximum exposure reduction with 1 mm lead equivalent, though heavy.

Occupational Radiation Monitoring

• Required for individuals at risk of receiving >1/10 the dose limit.

• Types of personnel monitors: film badges, TLDs, OSLs.

  • Film Badges: traditional and sensitive to temperature/humidity.

  • TLDs: more accurate, no loss of information.

  • OSLs: increased sensitivity and accuracy.

Report Requirements

• Monitoring reports to include current and cumulative exposure.

• Coordination of monitoring transfer when changing employment.

Guidelines for Radiation Safety

• During Imaging:

  • Maintain distance and utilize protective measures.

  • Follow ALARA (As Low As Reasonably Achievable) principles.

Special Considerations for Pregnant Workers

• Notify supervisor upon pregnancy declaration, with dose limits adjusted.

• Emphasis on minimizing exposure with secondary monitors.

Management Principles

• Incorporate robust training for new and existing employees on radiation safety.

• Encourage regular in-service training sessions focusing on radiation exposure and safety protocols.