Image Quality Improvements across Cone-Beam CT System Architectures

 

Cone-beam CT (CBCT), widely used in dentomaxillofacial and extremity imaging, is known to suffer from low soft tissue contrast resolution, strong image artifacts, and inaccurate

quantification of the x-ray attenuation. A new multi-source CBCT (ms-CBCT) was recently developed to overcome these limitations, using the novel distributed carbon

nanotube (CNT) field emission X-ray source array technology. The device can be operated under single energy or dual energy imaging mode. The purpose of this study was to compare the image quality of this new ms-CBCT with the conventional CBCT

  We compared (i) single-energy (SE) CBCT vs SE-ms-CBCT with same scanning protocal such as tube voltage and current and (ii) regular dual-energy CBCT (DE-CBCT) vs ms-CBCT

operating in the dual energy mode. An equine leg was scanned with these 4 different settings. After scanning, the processed projections were used for reconstruction using the 3D simultaneous Iterative Reconstruction Technique algorithm based on ASTRA Toolbox with total-variation and one-step decomposition for noise reduction. Both SE systems were reconstructed at 1×1×1 mm voxels. For DE system, Virtual Monoenergetic Imaging(VMIs) were generated from 50–150 keV (5keV steps) and the head-tohead comparison using 60 keV VMI with 1×1×3 mm voxels for DECBCT and DEMSCBCT. Fixed-size square Region of Interests(ROIs ) were placed in cortical bone and soft tissue regions. We recorded the mean HU and noise, computed contrast and contrast noise ratio (CNR).

  Here are the results: SE (~60 keV; 1-mm isotropic) CBCT yielded contrast 857.11 HU, noise 56.13 HU, CNR 15.29; msCBCT yielded contrast 969.38 HU, noise 46.44 HU, CNR 20.81—a ~36% CNR gain with ~17% lower noise at matched energy/resolution. DE (60 keV VMI; 1×1×3 mm): DEMSCBCT consistently showed lower noise (≈5–10%) and higher CNR (≈15–30%, depending on noise definition) than DECBCT, with the advantage persisting across the 50–150 keV sweep.

  With energy matched for SE (≈60 keV) and using VMI in 60keV in DE system for comparison, at matched scanning protocol and voxel size, DE imaging produced lower noise and higher CNR than SE. Within each acquisition paradigm, the multisource architecture further improved image quality, yielding lower noise and higher CNR than the corresponding single-source implementation.