As dental imaging technology advances, many practices are transitioning from an orthopantomogram (OPG) to a cone beam computed tomography (CBCT) system. While a CBCT offers superior diagnostic capabilities, it also introduces heightened safety concerns due to increased radiation exposure and scatter. It is critical for practices to fully understand these risks and adhere to potential additional shielding requirements, to protect staff and patients.
Increased radiation and scatter
CBCT systems emit significantly higher doses of radiation compared to OPG devices, and the larger Field-of-View capabilities inherently generate more scatter radiation. Scatter occurs when x-rays deflect off tissues, radiating or “scattering” secondary radiation into surrounding areas, posing a potential risk if not properly contained. This amplified scatter necessitates re-evaluating shielding measures to ensure that all areas meet strict dose constraints.
According to EPA Radiation Guideline 7, shielding must limit exposure to:
20 µSv per week for the public in adjacent areas.
100 µSv per week for occupationally exposed individuals.
Unlike OPGs, which often only require basic shielding (e.g., double-plasterboard walls), CBCT systems may demand additional shielding materials such as lead-lined walls, Gib-X plasterboard or barite board alternatives, and shielded doors/windows to mitigate the increased radiation and scatter.
Reassessing shielding and compliance
The shift from OPG to CBCT reclassifies many practices as medium-risk premises, requiring a more comprehensive radiation shielding assessment. A shielding plan is mandatory in most cases and must be reviewed and certified by an accredited Consulting Radiation Expert (CRE). The key considerations for shielding include the following:
X-ray tube voltage and workload: Higher voltages and increased workloads produce more scatter, requiring advanced shielding.
Distance to occupied areas: Shielding must account for adjoining rooms, including offices, reception, or public spaces.
Occupancy factors: Adjacent areas with high foot traffic or frequent use necessitate stronger shielding.
Future growth: Projected increases in patient volume should inform shielding designs to ensure sustained compliance.
For practices installing a CBCT system, these factors must be carefully documented in a shielding plan and aligned with regulatory standards outlined in Radiation Guideline 7, Section 6.
Practical steps for CBCT safety
Engage a Consulting Radiation Expert (CRE): A CRE will evaluate your premises and provide certified guidance on shielding design, materials, and installation.
Audit and upgrade shielding: Assess existing barriers and upgrade where necessary, incorporating lead sheets, GiB-X plasterboard, or shielded glass for observation windows.
Optimise layout: Position CBCT units to minimise scatter into high-traffic or commonly occupied areas.
Why a full shielding plan is critical
CBCT imaging operates at higher energy levels than OPGs, making proper shielding essential for achieving the ALARA principle (As Low As Reasonably Achievable). Failing to implement a comprehensive shielding plan not only risks non-compliance with NSW EPA regulations but also compromises the safety of patients and staff. Even practices with existing shielding may require retrofitting to meet the more stringent standards for CBCT.
Meeting regulatory requirements
Practices must ensure that shielding aligns with dose constraints detailed in Radiation Guideline 7. Self-assessments, which may suffice for OPG installations, are generally inadequate for CBCT systems. Shielding plans should include:
The maximum tube voltage and expected workload.
The type and level of radiation exposure (primary vs. scatter).
Detailed diagrams of the premises, showing radiation sources and adjacent areas.
Having a shielding plan completed and certified by a CRE ensures that the CBCT room and surrounding areas are adequately protected from the ionising radiation generated by the CBCT.
Upgrading from OPG to CBCT: Conclusion
Integrating a CBCT into your practice marks a significant step forward in patient care but requires an increased commitment to radiation safety. Transitioning from an OPG to a CBCT necessitates a full reassessment of shielding requirements to address increased radiation levels and scatter risks.
By adhering to the requirements of Radiation Guideline 7 and partnering with a CRE, practices can ensure compliance, protect everyone in the facility, and safely leverage the advanced diagnostic capabilities of CBCT technology.
Any questions? Feel free to reach out to our friendly team at Gamma Tech, your trusted radiation safety experts.
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