Essential radiation safety concepts for radiology residents preparing for boards and clinical practice, including ALARA, dose limits, and safety protocols.
Core Radiation Safety Principles
ALARA: As Low As Reasonably Achievable
The fundamental principle guiding all radiation use in medicine. Every examination should use the minimum radiation necessary to obtain diagnostic information.
Dose Limits & Regulations
Occupational Dose Limits
- Total Effective Dose: 50 mSv/year (5 rem/year)
- Lens of Eye: 150 mSv/year
- Skin/Extremities: 500 mSv/year
- Declared Pregnant Worker: 5 mSv (0.5 rem) to embryo/fetus during pregnancy
Public Dose Limits
Annual dose limit for members of the public: 1 mSv/year (0.1 rem/year)
Time, Distance, and Shielding
Time
Minimize exposure time. Dose is directly proportional to exposure duration.
Distance
Maximize distance from radiation source. Dose decreases with the inverse square of distance.
Shielding
Use appropriate barriers (lead aprons, mobile shields, structural shielding) to reduce exposure.
Fluoroscopy Safety
Operator Best Practices
- Use last image hold instead of continuous fluoroscopy
- Collimate to area of interest
- Maximize distance between patient and X-ray tube
- Minimize magnification mode use
- Wear lead apron, thyroid shield, and protective eyewear
Patient Safety
Pregnancy Screening
Establish protocols for identifying pregnancy before high-dose examinations. Know embryo/fetal dose thresholds for various effects.
Pediatric Considerations
Children are more radiosensitive. Use size-appropriate protocols and consider non-radiation alternatives when appropriate.
Exam Preparation
For RISC and NIS exams, memorize key dose limits, understand regulatory requirements, and be able to apply safety principles to clinical scenarios. RadCore's question bank provides extensive practice in radiation safety concepts.