Chapter 3: Radiation Safety

Chapter 3: Radiation Safety

Introduction to Radiation Safety

  • Warning: X-ray radiation poses significant risks.

Relevance of Radiation Safety Information

  • Protecting hospital and clinic staff from different types of radiation exposure:

    • Primary Radiation: Direct emission from the source.

    • Secondary Radiation: Radiation that scatters off objects or patients.

    • Scattered Radiation: Radiation dispersed in various directions after interacting with matter.

  • Ensuring the safety of patients and their owners regarding radiation dose during imaging procedures.

Radiobiology Overview

  • Cell Biology:

    • Mitosis: Process of cell division resulting in two identical daughter cells.

    • Meiosis: Specialized cell division forming genetic cells (gametes).

  • Impact of Radiation on Cellular Processes:

    • Radiation energy may disrupt normal cellular processes (mitosis and meiosis), causing varying degrees of effects depending on the stage and type of cell affected.

Effects of Radiation on Cells

  • Notable effects of radiation are observed at the cellular level and primarily impact DNA.

  • Gradations of Effects:

    • Concern for collective rather than isolated cell effects due to the nature of radiation exposure.

Types of Radiation Effects

  • Two Main Categories of Radiation Effects:

    1. Stochastic Effects:

    • Occur randomly, without a threshold level of exposure.

    1. Deterministic Effects (Non-stochastic):

    • Noticeable effects resulting from higher doses that occur in the short term.

Detailed Effects of Radiation on DNA

  • Four Possible Outcomes of Radiation Impact on DNA:

    1. Transmission Without Damage:

    • Radiation may pass through with no effect on critical cellular components, potentially suspending mitosis without causing cellular damage.

    1. Subsequent Damage:

    • No immediate effects but possible latent damage may arise, complicating later mitosis and potentially causing cell death.

    1. Visible Cellular Damage:

    • Observable damage in DNA structure, resulting in compromised functionality.

    1. Immediate Cell Death:

    • Cell death may occur from significant damage caused by a radiation strike on the DNA molecule.

Radioactivity Fundamentals

  • Nature of Radioactive Atoms:

    • Certain atoms with unstable nuclei emit particles and energy to achieve stability, a process referred to as radioactive decay or radioactive disintegration.

    • Imbalance in neutrons and protons causes nucleus instability.

Radiation Penetration and Energy Transfer

  • Radiation Penetration:

    • All radiation types can penetrate biological tissue and transfer energy, quantified as linear energy transfer (LET).

    • Higher LET values indicate greater energy transfer to tissue, with denser tissues like bone absorbing x-ray photons more effectively, reducing exposure to imaging receptors.

Measurement of Radiation Doses

  • Dosimeter Usage:

    • A dosimeter is essential for measuring radiation doses, especially for those regularly exposed in radiographic environments.

    • Personnel working in radiographic areas must wear personal dosimeters.

Types of Dosimeters

  • Thermoluminescent Dosimeters (TLDs): Measure radiation by storing energy from ionizing radiation.

  • Optically Stimulated Luminescence (OSL) Dosimeters: Measure radiation exposure through stimulated light emission.

Dosimeter Use Guidelines

  • Facilities must register healthcare worker information for effective dose tracking, accumulating data from various employers to calculate annual exposure.

Recommended Radiation Dose Limits

  • Dose Limits:

    • Specific dose limits are established for both radiation and non-radiation workers, with no gender discrimination for reproductive health.

    • Pregnant women require particular measures to protect the fetus from radiation exposure.

Key Radiation Units

  1. Absorbed Dose:

    • Formerly referred to as RAD, now measured in gray (Gy), indicating mass radiation absorption.

    • Minimal biological effect noted in diagnostic imaging contexts.

  2. Dose Equivalent:

    • Formerly REM, now termed sievert (Sv), used by personnel regularly exposed to radiation.

    • Dosimeters usually report in both REM and Sv.

  3. Measured Radiation:

    • Formerly roentgen, now termed air kerma (Gya), used for calibration of x-ray units, commonly reported in roentgens and milliroentgens.

Principles of Radiation Protection

  • Three Cardinal Rules:

    1. Time: Minimize exposure time, which is crucial in monitoring via personal dosimeters.

    2. Distance: Increase the physical distance from the radiation source to reduce intensity.

    3. Shielding: Position barriers between operators and radiation sources to diminish exposure.

Application of Radiation Protection Principles

  • Whenever possible, the operator should remain behind a shielding barrier during patient exposure.

Shielding Materials in Radiation Safety

  • Forms of Shielding:

    • Utilized leaded drapes and gonadal shields to protect patients during radiographic procedures.

    • Leaded aprons provide protection effectiveness at 125 kV radiation.

  • Protective Gear for Personnel:

    • Leaded gloves, aprons, and thyroid protectors are essential for staff during radiography.

    • Leaded glass goggles shield against secondary radiation exposure.

    • Movable lead barriers offer additional safety for personnel in high-risk areas.

Maintenance and Care of Protective Gear

  • Lead shielding materials are formed from layered thin sheets for effective protection.

  • Proper handling of leaded rubber sheets is critical to sustain durability over time.

Lead Specifications for Protective Apparel

  • Standards for Leaded Aprons and Gloves:

    • Radiographic and Fluoroscopic Leaded Aprons: Must have a minimum attenuation equivalent of 0.5 mm lead at 150 kV, clearly marked.

    • Leaded Gloves: Require 0.25 mm lead equivalency and must cover hands entirely, including fingers and wrists.

Additional Techniques for Radiation Exposure Mitigation

  • Immobilization Equipment:

    • Essential tools like radiolucent foam blocks and cloth restraints should be present to stabilize patients during imaging procedures.

Operational Conditions and Guidelines

  • Per regulations, only essential personnel should remain in the x-ray room during imaging to ensure safety.

  • Mechanical restraining devices should be employed for holding animals, with strict protocols for individual exposure monitoring.

  • Pregnant women and anyone under 18 should not hold animals or films during procedures.

Comprehensive Radiation Safety Rules Checklist

Checklist #1

  • Remove unnecessary personnel from the room during exposures.

  • Prohibit individuals under 18 or pregnant in the x-ray suite.

  • Rotate assisting staff to reduce exposure risk.

  • Use mechanical restraints whenever feasible.

  • Ensure protective apparel is worn (minimum 0.5 mm lead thickness).

  • Maintain proper usage and care for protective apparel to prolong lifespan.

  • Avoid body exposure to primary beam whether it is shielded or not.

Checklist #2

  • Employ collimation to reduce field size and minimize scatter radiation.

  • Never direct the x-ray beam toward personnel or adjoining populated rooms.

  • Place dosimeter badges near the collar to monitor thyroid, facial, and eye exposure.

  • Plan radiographic procedures meticulously to avoid retakes.

  • Ensure x-ray machines are calibrated as per state standards by licensed technicians.

Checklist #3

  • Maintain an exposure log documenting:

    • Patient information

    • Type of study

    • Exposure values

  • Adhere strictly to state safety codes.

  • Practice patience in procedural execution.

Key Points on Personnel Safety

  • Restraining personnel must avoid sitting on or leaning over the x-ray table.

  • Radiographers should maximize distance from patients during exposure.

  • All personnel present must wear adequate protective apparel.

  • Genetic damage often remains undetectable until observed in future generations.

  • Damage from high radiation doses is more severe compared to equivalent cumulative smaller doses.

  • Regular inspection is crucial for protective apparel to identify any wear-and-tear.