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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.

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