  With the emergence of swept-volume ultrasound (US) probes, precise and almost
real-time US volume imaging has become available. This offers many new
opportunities for computer guided diagnosis and therapy, 3-D images containing
significantly more information than 2-D slices. However, computer guidance
often requires knowledge about the exact position of US voxels relative to a
tracking reference, which can only be achieved through probe calibration. In
this paper we present a 3-D US probe calibration system based on a membrane
phantom. The calibration matrix is retrieved by detection of a membrane plane
in a dozen of US acquisitions of the phantom. Plane detection is robustly
performed with the 2-D Hough transformation. The feature extraction process is
fully automated, calibration requires about 20 minutes and the calibration
system can be used in a clinical context. The precision of the system was
evaluated to a root mean square (RMS) distance error of 1.15mm and to an RMS
angular error of 0.61 degrees. The point reconstruction accuracy was evaluated
to 0.9mm and the angular reconstruction accuracy to 1.79 degrees.

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