Probe calibration should be performed for free-hand tracking and ultrasound (US) fusion with a position sensor-attached US probe in US guided interventions. Difficulties in locating the probe imaging plane and adjusting the alignment of the probe with the calibration phantom call for more complicated and precise phantoms. However, the manufacture of such phantoms is time-consuming and expensive. Furthermore, the segmentation of the phantom features in US images cannot be reliably automated, which requires manual intervention. This paper presents a fully automatic 2D probe calibration method using a rather simple phantom. By detecting and analyzing the temporal signal arising from the ultrasound artifacts when sweeping the 2D probe over the phantom, the imaging plane of the probe and the image features can be reliably identified. Then the features are fed to a nonlinear optimizer to estimate the calibration parameters. The whole procedure including the setup can be done within 2 minutes with the fiducial registration error (FRE) of 0.16 mm. A US-guided biopsy experiment has also been conducted which shows the target registration error (TRE) of less than 1 mm.
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