Development and preliminary evaluation of a transducer guiding system for hand ultrasound: With a focus on reproducibility and operational stability

Various strategies have been proposed to reduce operator-dependent variability in musculoskeletal ultrasound, including mechanical stabilization techniques. However, their effects on image reproducibility and transducer handling remain unclear in anatomically complex regions such as hand. This two-phase study aimed to (1) develop and validate a transducer guiding system for hand ultrasound and (2) evaluate its influence on image reproducibility and operational stability through image-based analyses. In Phase I, test-retest reliability of the guiding system was examined by repeatedly measuring soft-tissue thickness in 30 healthy participants. Intraclass Correlation Coefficients (ICC) ranged from 0.766 to 0.948, demonstrating good to excellent reliability. In Phase II, 16 ultrasound users acquired images under handheld and guiding-system-assisted conditions based on predefined reference images. Image reproducibility was evaluated using Normalized Cross-Correlation (NCC) and ICC, while operational stability was assessed via cosine similarity derived from M-mode segments during the pre-capture period, with group comparisons performed using the Wilcoxon signed-rank test. Novice users showed substantial ICC improvement when using the guiding system (0.487-0.681), approaching the consistency observed in experienced users. Both novice and experienced groups displayed higher NCC and cosine similarity values with the guiding system, indicating improved reproducibility and operational stability. Overall, the guiding system enhanced image outcomes by providing standardized positioning and mechanical stabilization. These findings highlight its potential to improve consistency in hand ultrasound assessments and serve as a supportive tool for novice ultrasound training. The results further demonstrate the feasibility of mechanical stabilization in reducing operator-related variability and enhancing image consistency in hand ultrasound examinations.