Probe calibration problem

[CZHBD]

Hi

I have some probe calibration problems to consult, I used fcal to calibrate the probe, the error obtained in fcal is only about 1mm, but the actual error of the conversion matrix is about 5cm. I used an image capture card to collect ultrasound and 3D guidance as a tracker.

Do you have any tips and information as to how I can solve this? All replies will be greatly appreciated!