M-fiducial phantom based fast automatic ultrasound calibration technique: A novel approach for 2D to 3D image registration

This study introduces a novel M-fiducial phantom-based automatic ultrasound (US) calibration technique aimed at improving 2D to 3D image registration in ultrasound-guided procedures. The technique addresses limitations in existing methods by enhancing feature extraction capabilities and improving calibration accuracy. The proposed method utilizes an M-fiducial phantom, an extended version of the standard N-fiducial phantom, designed to facilitate automatic extraction with a linear probe, particularly in small field-of-view scenarios. A closed-form solution incorporating anisotropic scaling enables rapid and precise computation of transformation matrices for ultrasound calibration, and the method was tested across varying ultrasound depths to evaluate performance in point localization, length measurement, and volume estimation. Results show that the automatic extraction method, combined with the anisotropic closed-form solution, offers greater accuracy and reliability compared to manual methods. While in-plane measurements demonstrated high accuracy, out-plane estimations revealed potential limitations, especially with wire phantoms at increased depths. Despite these challenges, the M-fiducial phantom-based technique reduces operator workload and enhances ultrasound calibration precision, making it a promising approach for high-precision ultrasound-guided interventions. Future work should focus on refining the technique and validating its efficacy in clinical applications.