Actuator-Assisted Calibration of Freehand 3D Ultrasound System

Table 1

Comparison of calibration reproducibility among calibration approaches.

	Freehand cross wire	Actuator assisted cross wire	Actuator assisted collinear point targets	Actuator assisted modified collinear point targets	Acutator assisted cross wire (central region only)
Mean (SD)	1.50 (1.08)	0.84 (0.57)	1.72 (1.20)	1.50 (0.95)	4.91 (3.99)
Maximum	5.29	2.85	5.10	4.99	15.94
Minimum	0.043	0.042	0.13	0.077	0.14

For each approach, calibration reproducibility was calculated from 225 observations. All data in mm. One-way ANOVA revealed a significant difference among calibration approaches. Post hoc analysis further revealed that calibration reproducibility of the actuator-assisted cross wire phantom calibration was significantly better than that of the traditional freehand cross wire phantom calibration (). However, if actuator-assisted cross wire phantom calibration was only focused on the central region, it was significantly poorer than the traditional freehand cross wire phantom calibration (). Other actuator-based calibration approaches were not significantly different from the traditional freehand cross wire phantom calibration.