Deriving Hounsfield units using grey levels in cone beam computed tomography

TLDR

The study aimed to determine how grey levels in dental CBCT scanners correspond to Hounsfield units by imaging a phantom of eight known materials across 11 dental and 2 medical CT scanners. Phantom scans were performed under three conditions, exported as DICOM, and analyzed with On Demand 3D to establish a linear relationship between grey levels and linear attenuation coefficients. Linear regression of the reference materials yielded attenuation coefficients that enabled conversion of grey levels to Hounsfield units, demonstrating that HU can be derived from CBCT grey levels via linear attenuation coefficients.

Abstract

an in vitro study was performed to investigate the relationship between grey levels in dental cone beam CT (CBCT) and Hounsfield units (HU) in CBCT scanners.a phantom containing 8 different materials of known composition and density was imaged with 11 different dental CBCT scanners and 2 medical CT scanners. The phantom was scanned under three conditions: phantom alone and phantom in a small and large water container. The reconstructed data were exported as Digital Imaging and Communications in Medicine (DICOM) and analysed with On Demand 3D(R) by Cybermed, Seoul, Korea. The relationship between grey levels and linear attenuation coefficients was investigated.it was demonstrated that a linear relationship between the grey levels and the attenuation coefficients of each of the materials exists at some "effective" energy. From the linear regression equation of the reference materials, attenuation coefficients were obtained for each of the materials and CT numbers in HU were derived using the standard equation.HU can be derived from the grey levels in dental CBCT scanners using linear attenuation coefficients as an intermediate step.