Comparative Study of Ultrasound Shape Completion and CBCT-Based AR Workflows for Spinal Needle Interventions

TL;DR

This work addresses how imaging modality affects AR-guided spinal needle interventions by directly comparing ultrasound-based shape completion against CBCT-based AR workflows within a unified AR framework. The authors implement two pipelines—one using robotic ultrasound with probabilistic vertebral priors and shape completion, the other using AR-assisted CBCT planning and visualization—evaluated through a controlled phantom study with 20 participants. CBCT-AR consistently improves planning speed, insertion accuracy for deeper targets, usability, and trust, while US-AR offers radiation-free imaging but suffers from reliance on priors for deeper anatomy. The findings support a hybrid, multimodal AR strategy that leverages CBCT for global planning and ultrasound for intraoperative updates, with future work focusing on real-time fusion and in vivo validation.

Abstract

Purpose: This study compares two augmented reality (AR)-guided imaging workflows, one based on ultrasound shape completion and the other on cone-beam computed tomography (CBCT), for planning and executing lumbar needle interventions. The aim is to assess how imaging modality influences user performance, usability, and trust during AR-assisted spinal procedures. Methods: Both imaging systems were integrated into an AR framework, enabling in situ visualization and trajectory guidance. The ultrasound-based workflow combined AR-guided robotic scanning, probabilistic shape completion, and AR visualization. The CBCT-based workflow used AR-assisted scan volume planning, CBCT acquisition, and AR visualization. A between-subject user study was conducted and evaluated in two phases: (1) planning and image acquisition, and (2) needle insertion. Results: Planning time was significantly shorter with the CBCT-based workflow, while SUS, SEQ, and NASA-TLX were comparable between modalities. In the needle insertion phase, the CBCT-based workflow yielded marginally faster insertion times, lower placement error, and better subjective ratings with higher Trust. The ultrasound-based workflow achieved adequate accuracy for facet joint insertion, but showed larger errors for lumbar puncture, where reconstructions depended more heavily on shape completion. Conclusion: The findings indicate that both AR-guided imaging pipelines are viable for spinal intervention support. CBCT-based AR offers advantages in efficiency, precision, usability, and user confidence during insertion, whereas ultrasound-based AR provides adaptive, radiation-free imaging but is limited by shape completion in deeper spinal regions. These complementary characteristics motivate hybrid AR guidance that uses CBCT for global anatomical context and planning, augmented by ultrasound for adaptive intraoperative updates.

Figures (3)

• Figure 1: System Overview.
• Figure 2: Subjective ratings for the planning phase comparing the ultrasound-based AR (US-AR) and CBCT-based AR (CBCT-AR) workflows.
• Figure 3: Subjective ratings for the needle insertion phase comparing the US-AR and CBCT-AR.