Comparison of methods for acceptance and constancy testing in dental cone-beam computed tomography

Area of Science:

• Medical Imaging
• Radiology
• Quality Assurance

Background:

• Routine image quality (IQ) assurance is crucial for dental cone-beam computed tomography (CBCT).
• Two standards, the German DIN 6868-161 and the established IEC 61,223-3-5, are available for IQ assessment.
• Comparing these standards is essential for clinical practice.

Purpose of the Study:

• To implement, validate, and compare two IQ assurance procedures for dental CBCT.
• To evaluate the DIN 6868-161 and IEC 61,223-3-5 standards.
• To develop and test an automated quality assurance (QA) framework.

Main Methods:

• Determined in-plane modulation transfer function (MTF), contrast-to-noise indicator (CNI), and uniformity indicator (UI*) per DIN.
• Measured image noise, uniformity index (UI), contrast-to-noise ratio (CNR), and 3D MTF per IEC 61,223-3-5.
• Utilized a modular phantom on a clinical dental CBCT unit and implemented automated QA software.

Main Results:

• Automated phantom detection ensured reproducible measurements.
• Approximated and exact in-plane MTF calculations showed agreement within 5%.
• Image quality indicators (UI*, CNI, UI, CNR) demonstrated sensitivity to image artefacts, with significant drops observed at increased axial distances.

Conclusions:

• Implemented automated QA routines are compatible with both DIN and IEC approaches for dental CBCT.
• There is no direct equivalence between DIN and IEC metrics for IQ assessment.
• Conventional IQ parameters like noise, uniformity, and contrast are effective for evaluating image artefacts, and the automated QA program is suitable for clinical routine.