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Intro to Radiation Protection - Ch.9 Notes

Radiation Protection – Key Concepts (Ch.9)

  • Ionizing radiation interacts with water in the body, converting water to free radicals; these free radicals are more dangerous biologically than the radiation itself.

  • The overarching idea: the benefit of using radiation to diagnose disease must be weighed against the risks; the benefit often outweighs the risk when diagnosing and treating disease.

  • Responsibilities of the radiographer:

    • I. Ensure the minimal amount of radiation is used to produce a diagnostic-quality image.

    • Protect the patient from unnecessary radiation exposure (e.g., repeats) through practices like proper collimation and shielding.

    • Collimation: narrowing the beam to exclude unnecessary tissue; avoid exposing gonadal tissue unnecessarily.

    • Gonadal shielding: shielding ovaries and testes where appropriate.

    • Use radiation safety habits to protect the patient, staff, and the general public.

  • Ionizing Radiation basics:

    • Ionizing radiation travels via altering the state of atoms (adding or removing electrons).

    • In the x-ray tube, radiation is created every time the button is pressed.

    • An ion is a charged particle.

Ionizing Radiation and Its Biological Effects

  • Ionizing radiation interacts with water molecules in the body, producing free radicals; free radicals cause biological effects on cells.

Types of Ionizing Radiation

  • Particulate Radiation:

    • Alpha particles: from radioactive decay

    • Beta particles: medium/less massive; can travel some distance

  • Electromagnetic Radiation:

    • Gamma rays, x-rays, etc. (EM radiation in travel)

Detection and Measurement Devices (Dosimetry & Monitoring)

  • Dosimeters (Whole-body badges):

    • Worn on the body between the neck and the waist

    • If wearing a lead apron, use a dual badge strategy:

    • One badge on the collar (outside of the apron)

    • One badge under the apron

    • Faces of the badge should be oriented toward the radiation source (outer surface facing the source)

    • Dual badge setup ensures measurement of exposure with and without shielding

  • Field Survey Instruments:

    • Geiger–Mueller (G-M) counter: mainly used to detect the presence of radiation; widely used in nuclear medicine departments

Page 3–Reinforcement: Core Responsibilities and Practices

  • Reiterate the radiographer’s duties:

    • Use minimal exposure to obtain a diagnostic-quality image

    • Shield and collimation practices to reduce exposure to non-target tissues

    • Adhere to safety habits to protect patients, staff, and the public

  • Ionization definition reminder:

    • Ionization: changing the state of an atom by adding or removing electrons

    • Each x-ray exposure corresponds to an action created in the x-ray tube when the button is pressed

Scintillation and Ionization Chambers (Instrumentation)

  • Scintillation devices:

    • Primarily found in gamma cameras, nuclear medicine, and CT

  • Ionization chamber instruments:

    • Used to measure radiation and test output of imaging machines; can detect leakage and other outputs

Personal Monitoring Devices (PMD) and Dose Limits

  • Personal Monitoring Device (PMD) / Dosimeters:

    • Estimate the amount of exposure received by an individual

    • Annual occupational effective dose limit:

    • 50\,\mathrm{mSv} (equivalent to 5\,\mathrm{rem})

    • PMD is required when radiation workers are likely to receive 10% or more of the annual occupational effective dose; i.e., if the estimated exposure is ≥0.10\times 50\,\mathrm{mSv} = 5\,\mathrm{mSv} per year

    • Cannot exceed 50\,\mathrm{mSv} per year

Common PMD Types (4 most common)

  • OSL (Optically Stimulated Luminescence):

    • Common, detects small doses, durable, color coded monthly; worn on the body

  • Film Badge Dosimeter:

    • Inexpensive, durable, good record keeping; gradually becoming obsolete

  • TLD (Thermoluminescent Dosimeter):

    • Common, accurate in lower doses; often used as a ring badge

  • Pocket Dosimeter:

    • Not very common due to lack of permanent record; good for immediate readouts during large exposures

Electronic Digital Dosimeters (Newer Technology)

  • Resemble a USB jump drive; data input to computer

  • Software processes, extracts, and calculates dose

  • More expensive; considered the future of dosimetry

  • Can provide daily readings with a permanent record stored in computer systems

Important Guidelines for Dosimeters

  • Wear your dosimeter between the chest and waist level

  • Place the dosimeter outside of the lead apron (unshielded side towards the source)

  • Do not share dosimeters

  • Wear for the appropriate amount of time to reflect your exposure accurately

  • Store dosimeters in controlled conditions to avoid interference

Secondary Considerations and Environment

  • Secondary radiation areas and primary x-ray exposure considerations

  • Never wear a dosimeter when you are getting a personal diagnostic x-ray (e.g., dental x-ray)

  • Dosimeters can be affected by environmental factors:

    • Heat, pressure, humidity, exposure to light

  • Report any unusual events or readings to the radiation safety office

Practical and Ethical Implications

  • The ALARA principle: As Low As Reasonably Achievable should guide practice

  • Balancing patient care with radiation safety: minimize dose while maintaining diagnostic quality

  • Safety culture: consistent use of shielding, collimation, monitoring, and reporting

Summary of Core Definitions and Concepts

  • Ionizing radiation: radiation capable of removing or adding electrons to atoms, creating ions

  • Free radicals: highly reactive atoms/molecules formed by radiolysis of water; major driver of biological damage

  • Shielding and collimation: key methods to protect non-target tissues and reduce dose

  • PMDs and dose limits: standardized monitoring and caps to regulate occupational exposure

  • Instrumentation: detectors (G-M counters), dosimeters (OSL, Film, TLD, Pocket), and advanced electronic dosimeters for real-time data

Quick Reference Numbers and Points

  • Annual occupational dose limit: 50\,\mathrm{mSv} (equivalent to 5\,\mathrm{rem})

  • PMD required if exposure is ≥ 5 mSv/year (10% of the limit)

  • Common PMD types: OSL, Film Badge, TLD, Pocket Dosimeter; Electronic Digital Dosimeter as a future option

  • Placement guidelines: outside lead apron; wear between chest and waist; do not share; guard against heat, humidity, light exposure

  • Detection tools: Geiger–Mueller counters for presence, dosimeters for dose measurement, scintillation devices in gamma cameras/nuc med/CT