The authors have declared that no competing interests exist.
The combination of ultrasonography (US) and cone beam computed tomography (CBCT) has been proposed as a multimodal imaging strategy capable of uniting realtime softtissue assessment with highresolution threedimensional visualization of osseous structures. This study critically evaluated whether such integration provides measurable diagnostic or workflow advantages in mandibular imaging. Despite strong theoretical justification, the combined use of US and CBCT failed to demonstrate clinically meaningful improvements in diagnostic accuracy, confidence, or efficiency when compared with CBCT alone. Fundamental physical mismatches, hardware incompatibilities, geometric constraints, and operatordependent variability limited the anticipated synergistic benefits. These negative findings underscore the importance of reporting unsuccessful integration attempts to guide future research and prevent premature clinical adoption of technically incompatible imaging paradigms.
Accurate imaging of the jaws is essential in dentistry, oral and maxillofacial surgery, orthodontics, and periodontology.
However, CBCT and US are based on fundamentally different physical principles, acquisition geometries, and reconstruction assumptions. While hybrid use at the workflow level, via sequential acquisition and softwarebased image fusion, is feasible, the development of a truly integrated or synergistic CBCT–US system remains technically and clinically challenging. This study evaluates the practical outcomes of combining US and CBCT for mandibular imaging and reports predominantly negative results.
Ultrasonography is a noninvasive imaging modality that employs highfrequency acoustic waves to generate realtime images of soft tissues. In maxillofacial applications, US has been used to assess salivary gland pathology, superficial infections, vascular lesions, and softtissue masses.
Ultrasound imaging relies on the emission and reception of sound waves that reflect and scatter at interfaces with differing acoustic impedance. Image formation depends on timeofflight and amplitude of returning echoes, assuming relatively uniform sound speed and limited scattering along the propagation path. These assumptions are frequently violated in regions containing bone, air, or complex interfaces.
· Realtime dynamic imaging of soft tissues
· Absence of ionizing radiation
· Portability and costeffectiveness
· Ability to differentiate cystic and solid lesions
· Utility for imageguided aspiration or biopsy
Despite its advantages, ultrasonography is severely limited in osseous imaging by poor penetration through cortical and trabecular bone, strong reflection at bone–air interfaces, and high operator dependence. Lack of standardized osseous protocols, susceptibility to motion, geometric distortion, and challenges in reproducible image registration further reduce its reliability when integrated with tomographic modalities.
CBCT is a threedimensional radiographic technique widely used in dental and maxillofacial imaging. It provides highresolution visualization of osseous structures with lower radiation dose than conventional medical CT.
CBCT systems acquire multiple twodimensional projections using a coneshaped Xray beam during gantry rotation. Reconstruction algorithms assume straightline photon propagation and stable voxel attenuation values, enabling volumetric reconstruction through filtered backprojection or iterative techniques.
· High spatial resolution for bony anatomy
· Accurate threedimensional representation
· Essential for implant planning and surgical guidance
· Lower radiation dose relative to conventional CT
CBCT exhibits poor intrinsic softtissue contrast, susceptibility to scatter and beamhardening artifacts, and limited ability to characterize nonmineralized tissues. These limitations have motivated interest in complementary modalities such as ultrasonography.
The proposed integration of US and CBCT aims to combine softtissue and hardtissue information into a unified diagnostic framework. In practice, integration was limited to sequential acquisition and softwarebased fusion rather than simultaneous hardware integration.
While theoretical advantages include comprehensive tissue assessment and improved diagnostic confidence, practical implementation revealed significant limitations. Increased acquisition time, registration errors, operator variability, and minimal incremental diagnostic value outweighed any perceived benefit.
Clinical scenarios evaluated included salivary gland disease, TMJ disorders, vascular lesions, and mixed soft and hardtissue pathologies. In most cases, ultrasonography provided limited additional information beyond CBCT findings, except for superficial softtissue abnormalities.
Fundamental mismatches between Xray attenuationbased tomography and acoustic wavebased imaging prevent true synergy. CBCT assumes static geometry and linear attenuation, whereas ultrasonography depends on dynamic probe positioning, tissue compression, and heterogeneous sound propagation.
CBCT requires rigid gantry rotation with fixed source–detector geometry, while ultrasonography demands direct tissue contact and free probe manipulation. These requirements are mutually incompatible within a single acquisition system, precluding true hardware integration.
The study demonstrated that:
· Ultrasonography rarely added clinically relevant information beyond CBCT
· Bone interference prevented consistent anatomical correlation
· Combined workflows increased procedure time
· Interoperator variability reduced reproducibility
Collectively, these findings indicate that US does not meaningfully enhance CBCTbased mandibular imaging under current technological constraints.
Future progress may depend on advances in artificial intelligenceassisted registration, improved a coustic penetration techniques, standardized imaging protocols, and novel hybrid physics approaches such as Xrayinduced acoustic imaging. Until such developments mature, routine integration remains unjustified.
Despite strong theoretical appeal, the integration of ultrasonography and CBCT for mandibular imaging failed to demonstrate measurable clinical benefit in this negative results study. Fundamental physical, geometric, and operational incompatibilities limit meaningful synergy between these modalities. Reporting these negative findings contributes to scientific transparency and provides realistic guidance for future research in multimodal imaging.