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Radiation Safety

Radiation safety in nuclear cardiology follows two principles:

  1. Perform the examination only when clinically justified.
  2. Keep exposure as low as reasonably achievable (ALARA) while preserving diagnostic quality.

Time, Distance, and Shielding

  • Time: minimize time near radioactive sources and recently injected patients.
  • Distance: exposure falls rapidly as distance increases.
  • Shielding: use syringe shields, transport containers, barriers, and appropriate storage.

Prepare supplies before handling activity to reduce unnecessary exposure time.

Occupational Dose Limits

Federal NRC limits for adult radiation workers include:

Exposure Annual limit
Total effective dose equivalent 50 mSv
Lens of the eye 150 mSv
Skin or extremity 500 mSv
Member of the public 1 mSv

For a worker who voluntarily declares pregnancy in writing, the embryo/fetal occupational dose limit is 5 mSv for the entire pregnancy.

These are regulatory ceilings, not exposure targets. Institutional and state requirements may be more restrictive.

Personnel Monitoring

Wear assigned dosimeters correctly:

  • Whole-body badge between the neck and waist
  • Ring badge on the hand most likely to receive exposure
  • Fetal badge at waist level when required after pregnancy declaration

Do not share badges or intentionally expose them. Report unusual readings or suspected exposure promptly to the radiation-safety officer.

Reducing Patient Dose

  • Confirm that the study is appropriate.
  • Avoid duplicate testing.
  • Use the lowest activity that provides diagnostic images.
  • Use weight-adjusted protocols when appropriate.
  • Prefer stress-first or stress-only imaging in suitable patients.
  • Use attenuation correction and modern reconstruction.
  • Use high-efficiency cameras when available.
  • Avoid unnecessary dual-isotope protocols.
  • Limit CT attenuation-correction exposure to what is required.
  • Encourage hydration and frequent voiding after the study when appropriate.

A technically inadequate low-dose study that must be repeated does not improve safety.

Pregnancy

Determine pregnancy status before radiopharmaceutical administration when pregnancy is possible and the result would affect management.

If pregnancy is known or suspected:

  • Confirm that imaging is clinically necessary.
  • Consider ultrasound, echocardiography, or MRI when appropriate.
  • Involve nuclear medicine and medical physics or radiation safety.
  • Estimate fetal dose when needed.
  • Document the risk-benefit decision.

Pregnancy is not an absolute prohibition when the examination is urgently necessary, but elective studies should generally be deferred or replaced.

Breastfeeding

Ask about breastfeeding before administration.

Interruption recommendations depend on:

  • Radiopharmaceutical
  • Administered activity
  • Physical and biologic half-life
  • Institutional policy

Provide tracer-specific written instructions. Do not use a single interruption period for every nuclear medicine examination.

Contamination and Spills

Prevent contamination by using gloves, absorbent pads, labeled containers, and appropriate waste disposal.

If a spill occurs:

  1. Stop and restrict access.
  2. Prevent spread of contamination.
  3. Notify nuclear medicine and radiation safety.
  4. Remove contaminated clothing when appropriate.
  5. Survey the area and affected personnel.
  6. Decontaminate according to institutional policy.
  7. Document the event.

Do not leave the area or spread contamination before being surveyed.

Extravasation

Radiotracer extravasation may:

  • Increase local radiation exposure
  • Reduce delivered activity
  • Degrade image quality
  • Alter quantitative measurements

Document the injection site and degree of infiltration. Repeat imaging or reinjection should be individualized rather than automatic.

Patient Instructions

After routine diagnostic myocardial perfusion imaging:

  • Maintain hydration when not medically contraindicated.
  • Void frequently.
  • Follow any tracer-specific breastfeeding instructions.
  • Follow facility guidance regarding contact with infants or pregnant individuals.

Most routine diagnostic studies do not require isolation, but instructions should follow the administered tracer and local policy.

Key Points

  • Apply ALARA through justification, optimization, and avoidance of repeats.
  • Time, distance, and shielding protect personnel.
  • Dose limits are ceilings, not goals.
  • Screen for pregnancy and breastfeeding before injection.
  • Use tracer-specific instructions.
  • Follow institutional radiation-safety procedures for spills and unusual exposures.

References

  1. NRC Standards for Protection Against Radiation — 10 CFR Part 20
  2. ASNC SPECT Protocols and Tracers Guidelines
  3. Nuclear Medicine and Radiation Safety — SNMMI