Improving Hounsfield Unit accuracy in dental CBCT through the integration of 2D anti-scatter grid

Lack of Hounsfield Unit (HU) accuracy leads to misrepresentation of tissue densities and causes image artifacts in dental cone beam computed tomography (CBCT) images. This work investigates the improvement in HU accuracy in dental CBCT by suppressing scatter with a novel two-dimensional anti-scatter grid (2D ASG) approach.

A 2D ASG prototype was developed and integrated into an experimental CBCT system, emulating dental CBCT geometry. CBCT scans were acquired using a multidetector CT (MDCT), a clinical dental CBCT, and the proposed 2D ASG-based experimental CBCT system. Subsequently, HU accuracy, nonuniformity, and contrast-to-noise ratio (CNR) were evaluated in image quality phantoms benchmarked against MDCT images. The effect of scatter suppression on the implant-induced HU degradation was also studied.

2D ASG reduced scatter content up to a factor of 6.6 in CBCT scans and HU nonuniformity in soft tissue-like regions was reduced from 23 to 4 HU. HU errors in high-density structures were within 65 HU of values measured in the gold standard MDCT images. Robust scatter suppression also reduced streak artifacts caused by implants. CNR increased up to 47% in images acquired with the 2D ASG.

HU accuracy in dental CBCT may reach the accuracy of MDCT with the proposed 2D ASG. Moreover, artifacts are reduced, and contrast visualization can be improved. Hence, this approach may enable a more accurate assessment of tissue densities in CBCT images, and improved image quality may positively impact the diagnostic capabilities of dental CBCT systems.