REAL-TIME FREEHAND 3D ULTRASOUND CALIBRATION
Po-Wei Hsu, Richard W. Prager, Andrew H. Gee and Graham M. Treece
Z-fiducial phantoms allow 3D ultrasound probe calibration with a single B-scan. One of the main hindrances of using this phantom is the necessity of segmenting the wires reliably, which requires human intervention. In this paper, we have shown how we can solve this problem by mounting a thin rubber membrane on top of the phantom. The membrane is segmented automatically and the wires can be easily located as they are at known positions relative to the membrane. This enables us to segment the wires automatically at the full PAL frame rate of 25Hz, to produce calibrations in real-time, while achieving accuracies similar to those reported in the literature. We also devise a technique to improve the estimation of the elevational offset by capturing a few images of the planar membrane. If spatial calibration is known, fully automatic wire segmentation allows the fiducials to be tracked in real-time. This also enables temporal calibration to be performed in real-time as the probe is moved away from the phantom.
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