Abstract
Ultrasonography (US) is a widely used, real-time imaging modality; however, its effectiveness in the head and neck region can be limited by the complexity of anatomical structures and the operator's experience. Mixed reality (MR) technology, utilizing head-mounted displays (HMDs) to overlay 3D holographic models onto the real environment, has shown potential in medical applications. This preliminary study aims to evaluate a prototype HMD-based system that supports US examinations by providing enhanced spatial guidance through MR visualization. A soft tissue phantom embedded with artificial lesions was scanned with CT to create DICOM datasets, which were reconstructed into 3D holographic models. These models were displayed via a custom MR application developed in Unity Technologies (San Francisco, CA, USA) and operated on Microsoft HoloLens 2 (Microsoft Corp., Redmond, WA, USA). Six sonographers were assigned to two groups: Group A (conventional US) and Group B (HMD-assisted US). Each participant performed a scanning task to identify target lesions. Task performance was assessed using two quantitative metrics: the time to complete the scanning task and the number of missed or falsely identified lesions. Statistical analysis was performed using a t-test, with significance set at p < 0.05. Group A relied more on wide scanning and screen observation, whereas Group B focused on holographically indicated regions. The mean task times were 178 seconds for Group A and 293 seconds for Group B, with no significant difference (p = 0.21). Clinical experience was negatively correlated with task time (R = -0.71), indicating that more experienced operators completed the task more quickly. Although Group B showed a trend toward fewer missed or false-positive lesions, this did not reach statistical significance (p = 0.076). The HMD-based MR guidance system provides a feasible approach to support lesion targeting in US examinations. The findings from this preliminary phantom study suggest that MR technology may complement conventional US by enhancing spatial awareness during scanning procedures.