Routine quality control by facility staff is essential, but periodic evaluation by a qualified medical physicist provides an independent, quantitative assessment of CBCT performance. RadSite spoke with Phillip W. Patton, PhD, CHP, DABR, DABSNM, Chief Physics Officer, about how physics testing supports image quality, radiation-dose optimization, equipment reliability, and accreditation. Specific tests and requirements may vary by system, clinical application, manufacturer, jurisdiction, and accreditation program.
What is physics testing, what does it evaluate, and why is it important for CBCT systems?
Dr. Patton: Physics testing is a comprehensive equipment performance evaluation conducted by a qualified medical physicist. Using calibrated instruments and phantoms or other appropriate test objects, the physicist evaluates radiation output, image quality, equipment performance, and safety.
In addition to routine testing, the physicist may perform quality control tests that are not routinely performed by the facility. These may include assessing radiation dose and characterizing the X-ray beam. This helps verify that the system’s radiation output and dose estimates remain within expected ranges and are appropriate for the image quality required.
How does physics testing differ from routine quality control performed by the facility or operator?
Dr. Patton: Routine quality control is performed by trained facility personnel at prescribed intervals to monitor the system for day-to-day or week-to-week changes. Physics testing is a more comprehensive, quantitative evaluation conducted by a qualified medical physicist using calibrated instruments and specialized or standardized phantoms. The physicist compares the findings with established baselines, action limits, manufacturer specifications, and applicable standards.
What should a facility expect when a physicist comes onsite to perform testing, and how disruptive is the process to normal operations?
Dr. Patton: Testing often takes approximately one hour per CBCT unit, although the time required may vary depending on the system, number of protocols, scope of testing, and findings. The unit generally will not be available for patient imaging during that period, but the evaluation should cause minimal disruption when appropriately scheduled.
What can physics testing reveal about a CBCT system that may not be noticeable during everyday use, and how can it help identify problems before they affect image quality, patient care, or become more costly?
Dr. Patton: Physics testing can identify subtle performance drift—such as changes in radiation output, alignment, calibration, image uniformity, resolution, or artifacts—that may not be apparent during everyday clinical use. Catching these issues early gives the facility a chance to correct them before they affect patient care, lead to repeat scans, cause unexpected downtime, or develop into more costly problems.
How does physics testing relate to radiation dose and patient safety?
Dr. Patton: Physics testing helps confirm that radiation output is accurate, reproducible, and appropriate for the clinical protocols being used. It also supports optimization—using the lowest radiation exposure that still produces image quality adequate for the clinical task.
How can regular physics testing support the reliability and overall performance of a CBCT system?
Dr. Patton: Physics testing does not replace preventive maintenance, but tracking results over time can identify performance changes and prompt service or corrective action before a problem becomes clinically significant or causes avoidable downtime. Depending on the CBCT system, testing may evaluate factors such as mechanical accuracy, alignment, collimation, radiation output, and image quality. Tracking these measures over time can help identify trends and support timely maintenance or corrective action.
How does physics testing support CBCT accreditation, and why should a practice view it as more than simply a regulatory or accreditation requirement?
Dr. Patton: Physics testing is an important component of CBCT accreditation because it provides objective documentation that equipment performance has been evaluated against applicable standards and that identified deficiencies have been addressed. It complements routine facility quality control, preventive maintenance, clinical image review, and the other elements assessed through accreditation. Practices should therefore view it not simply as a requirement, but as an opportunity to strengthen imaging quality and patient safety.
How often should a CBCT system undergo physics testing, and what documentation should a practice maintain following testing?
Dr. Patton: A comprehensive physics evaluation should be performed at installation or acceptance and at least annually thereafter, subject to applicable regulations, accreditation requirements, and manufacturer recommendations. Additional evaluation may be appropriate following major repairs, relocation, or other significant changes that could affect system performance. The practice should retain the signed physics report, testing results and comparisons with applicable baselines or tolerances, routine quality-control records, relevant service documentation, identified deficiencies, corrective actions, and evidence that the deficiencies were resolved.
What are the biggest benefits of physics testing for facilities, providers, and patients?
Dr. Patton: Facilities gain objective evidence of system performance and earlier warnings of potential problems. Providers gain confidence that the images are technically reliable for diagnosis or treatment planning. Patients benefit from appropriately optimized radiation exposure and a reduced risk of avoiding repeat examinations.
What is one piece of advice you would give to a facility or practice operating a CBCT system about the importance of physics testing?
Dr. Patton: Physics testing is an important part of maintaining a CBCT system and supporting patient safety. The physicist is a valuable member of the team who can often identify issues before they become larger problems. Think of physics testing as helping take care of both your system and your patients.
Do not treat physics testing as a once-a-year paperwork exercise. Review the report with your team, address every finding, and use the physicist as an ongoing resource. The goal is not simply to pass a test, but to maintain a system that consistently produces dependable images at an appropriate radiation dose.