Enhancing transcranial Doppler imaging through tracked 3D volumetric reconstructions

Transcranial Doppler (TCD) ultrasound is a portable, non-ionizing imaging modality widely used for real-time monitoring of cerebral blood flow in applications such as vasospasm detection, emboli tracking, autoregulation assessment, and brain death confirmation. However, conventional TCD systems lack anatomical context, are highly operator-dependent, and exhibit inconsistent angle alignment, thereby limiting measurement accuracy and reproducibility. This feasibility study presents a tracked, freehand 3D Doppler ultrasound system that reconstructs volumetric blood flow maps using electromagnetic tracking and standard clinical ultrasound platforms. Four adult subjects were scanned through bilateral transtemporal acoustic windows, and 600–1000 Doppler frames were collected per subject following spatial calibration. Volumetric reconstructions were generated offline, and vessel diameters were measured from orthogonally reformatted axial views of the M1 and P1 segments. Measured values showed a strong correlation with Digital Subtraction Angiography (DSA)-based normative values (Pearson r = 0.99, p=0.0093), with standard deviations < 0.35mm across all segments. Expert neurologists confirmed anatomical consistency of the bilateral MCA, PCA, and ACA reconstructions across all subjects. These findings support the potential of tracked 3D Doppler ultrasound as a non-invasive, real-time imaging modality for intracranial vascular assessment. The ability to generate co-registered volumetric maps with anatomical context addresses key limitations of conventional TCD, including operator dependence and lack of spatial guidance. Retrospective visualization enables correction of insonation angle and vessel localization even in the presence of anatomical distortion. This framework also lays the groundwork for automated or semiautomated acquisition workflows, enabling standardized, reproducible imaging in neurocritical care and bedside cerebrovascular monitoring.