Geometric calibration aims to determine the transformation between the ultrasound image plane coordinate system and the sensor coordinate system attached to the probe. In order to solve the problem of obtaining high-accuracy and robust results intended for labor guidance usage, this study designed an automatic freehand ultrasound calibration system with minimal human interaction combined with electromagnetic tracking. In this system, a multilayer N-wire phantom was utilized, and an auxiliary bracket was designed to hold the ultrasound probe during data collection. Moreover, a completely automatic algorithm was proposed for fast image segmentation. Calibration quality was validated by calculating precision and accuracy. Results Extensive trials were also conducted. On average, the calibration accuracy was 1.42 mm, and the precision was 1.29 mm. These results suggest that precision and accuracy achieved with optimized multilayer N-wire phantoms can be more precise compared to other methods. Furthermore, the high-accurate and robust results demonstrate the freehand 3D ultrasound system can accurately track target anatomy during labor guidance.

Jingbo Rong, Yaosheng Lu, Shucheng Qin, Rongdan Zeng. Geometric Calibration of Freehand Ultrasound System with Electromagnetic Tracking. Academic Journal of Computing & Information Science (2020), Vol. 3, Issue 3: 117-128. https://doi.org/10.25236/AJCIS.2020.030313.

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