Coplanarity Constrained Ultrasound Probe Calibration Based on N-Wire Phantom

Area of Science:

• Medical Imaging
• Biomedical Engineering
• Computer Vision

Background:

• N-wire phantom calibration is crucial for freehand tracked ultrasound imaging systems.
• Current methods using least squares are sensitive to outliers and disregard fiducial point coplanarity.
• Existing techniques can lead to reduced calibration accuracy and precision.

Purpose of the Study:

• To introduce a novel coplanarity-constrained calibration algorithm for N-wire phantom-based ultrasound probe calibration.
• To overcome the limitations of existing methods, specifically outlier sensitivity and loss of coplanar information.
• To enhance the precision and accuracy of ultrasound probe calibration.

Main Methods:

• Verified normal distribution of out-of-plane error along the oblique wire in N-wire phantoms.
• Utilized Levenberg-Marquardt algorithm for outlier removal and plane fitting.
• Projected points onto the fitted plane along the oblique wire and employed coplanarity-constrained registration for transformation matrix calculation.

Main Results:

• The proposed method demonstrated superior calibration precision compared to closed-form and in-plane error methods.
• Achieved 25% and 36% improvement in mean calibration accuracy at depth 16, respectively.
• Algorithm showed better performance across various depths in experimental setups.

Conclusions:

• The coplanarity-constrained calibration algorithm significantly improves precision and accuracy over existing methods using N-wire phantoms.
• The findings are expected to enhance calibration accuracy in other N-wire phantom-based procedures.
• This advancement contributes to more reliable freehand tracked ultrasound imaging.