Enforcement Policy for Positive-Beam Limitation Requirements in Diagnostic X-Ray Systems
This guidance outlines the enforcement policy for Positive-Beam Limitation (PBL) requirements in diagnostic X-ray systems following the May 3, 1993 amendment to the Performance Standard. The amendment allows assemblers to install manual beam-limiting devices (BLD) in stationary, general-purpose radiographic x-ray (GP) systems, eliminating the mandatory PBL requirement while maintaining PBL requirements for systems equipped with it.
What You Need to Know? 👇
What are the current FDA requirements for Positive-Beam Limitation (PBL) in diagnostic X-ray systems?
Since June 2, 1993, FDA eliminated the requirement that general-purpose radiographic systems must have PBL. Assemblers can now install manual beam-limiting devices instead. However, systems equipped with PBL must still comply with all applicable PBL requirements.
Can medical device owners modify their PBL systems without FDA approval?
Yes, under 21 CFR 1020.30(q)(2), owners can modify their diagnostic X-ray systems, including disabling PBL for manual operation, provided the modification doesn’t cause non-compliance with applicable regulations and the modification details are properly recorded.
How should compliance testing be conducted for X-ray systems with manual beam-limiting devices?
For general-purpose systems with manual BLD and X-ray tables, use the Abovetable X-Ray Source Radiographic procedure but skip PBL testing sections. For systems without tables, use the Vertical Cassette Radiographic procedure. PBL absence won’t constitute a violation.
What enforcement actions apply when PBL systems fail to function properly?
If PBL was non-functional since installation, it’s a valid noncompliance for fully certified systems. However, if users disabled PBL after installation per regulations, it’s not a violation. Proper documentation and testing procedures must distinguish between these scenarios.
How do small target angle X-ray tubes affect PBL sizing requirements compliance?
Small target angle tubes may have field coverage limitations at certain source-image receptor distances. FDA considers undersizing under these specific geometric conditions unlikely to pose public health concerns, though technical compliance with PBL sizing requirements still applies.
What testing modifications are needed for large field image intensifiers in AERC mode?
When testing maximum entrance exposure rate with large image intensifiers, ensure complete beam blockage with lead sheets. Position lead closer to X-ray tube or reduce field size to slightly larger than the measurement chamber to achieve proper maximum EER readings.
What You Need to Do 👇
Recommended Actions
- Update testing procedures based on system configuration (with/without table, PBL/manual BLD)
- Document any user modifications to PBL systems
- Implement proper testing methods for maximum EER measurements with large field image intensifiers
- Consider field coverage limitations when testing systems with small target angle X-ray tubes
- Maintain records of installation dates and system modifications
- Ensure compliance with applicable Performance Standard requirements for systems equipped with PBL
- Train testing personnel on the updated requirements and procedures
Key Considerations
Non-clinical testing
- Routine testing of GP systems with x-ray table should continue using Abovetable X-Ray Source Radiographic Systems (AR) test procedure
- For GP systems without table and equipped with manual BLD, use Vertical Cassette Radiographic Systems (VC) test procedure
- For GP systems without table but equipped with PBL, use Chiropractic Supplement to the AR procedure (ARB)
- Verify PBL mode functionality at installation and during testing
Safety
- PBL systems must prevent exposure until proper collimation is achieved
- PBL must operate correctly at designated source-image receptor distances (SID)
- Users can modify systems under 21 CFR 1020.30(q)(2) if modifications don’t result in non-compliance
Other considerations
- Maximum Entrance Exposure Rate (EER) measurements must be properly conducted for large field image intensifiers
- Special considerations apply for small target angle X-ray tubes regarding field coverage limitations
Relevant Guidances 🔗
- Radiation Control Requirements and Interpretations for Diagnostic X-ray Equipment
- X-Ray Equipment Performance Standards and Radiation Safety Requirements
- Safety and Performance Requirements for Cabinet X-ray Security Screening and Industrial Quality Control Systems
- Harmonization of Performance Standards for Diagnostic X-Ray Imaging Systems and Components with IEC Standards
- Performance Standards for Diagnostic X-Ray Systems and Major Components
Related references and norms 📂
- 21 CFR 1020.31(g): Performance Standard for Diagnostic X-Ray Systems and Their Major Components
- 21 CFR 1020.30(q)(2): Modifications by system owners
Original guidance
- Enforcement Policy for Positive-Beam Limitation Requirements in Diagnostic X-Ray Systems
- HTML / PDF
- Issue date: 1993-10-13
- Last changed date: 2020-03-17
- Status: FINAL
- Official FDA topics: Medical Devices, Radiation-Emitting Products, Postmarket, Investigation & Enforcement
- ReguVirta ID: 13de13b96f0d69900fe33542aa95c115