An investigation into dose optimisation for imaging root canal anatomy using cone beam CT

Area of Science:

• Dental Radiology
• Cone Beam Computed Tomography (CBCT)
• Endodontics

Background:

• Cone beam CT (CBCT) is crucial for visualizing complex root canal anatomy.
• Optimizing CBCT imaging parameters is essential for balancing diagnostic image quality and patient radiation dose.
• Identifying diagnostically acceptable dose levels and image quality thresholds is a key challenge in CBCT endodontics.

Purpose of the Study:

• To establish the lowest diagnostically acceptable radiation dose and image quality threshold for CBCT imaging of root canals.
• To evaluate these parameters using maxillary first molar (M1M) second mesiobuccal (MB2) canals of varying complexity.
• To compare the performance of two different CBCT scanners in achieving diagnostic image quality at reduced doses.

Main Methods:

• Dose-area product (DAP) and contrast-to-noise ratio (CNR) were measured across a range of exposure parameters for two CBCT scanners.
• Subjective image quality was assessed by nine raters (endodontists, dental radiologists, junior staff) using a 5-point confidence scale for visibility of MB2 canals in an anthropomorphic phantom.
• Three M1Ms with varying MB2 canal complexity were used for the image quality assessments.

Main Results:

• Diagnostic image quality for simple-to-moderate MB2 canal complexity was achieved with specific DAP and CNR values for both scanners.
• Increasing radiation dose did not improve the visualization of complex root canal anatomy on either CBCT scanner.
• Junior staff rated significantly more images as undiagnostic compared to senior staff (p = 0.043).

Conclusions:

• A similar threshold dose was identified for both CBCT scanners for M1Ms with simple-to-moderate MB2 canal complexity.
• Higher radiation doses were ineffective in enhancing the visualization of more complex root canal anatomy.
• Selecting standard CBCT protocols over high-resolution scans is a practical approach to reduce patient dose, and CNR is not a universally transferable measure of image quality.