Surface-based registration of physical space with CT images using A-mode ultrasound localization of the skull
W. Andrew Bass, Robert L. Galloway, Calvin R. Maurer · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 1998
A method is described for computing the registration of computed tomography (CT) images of the head with physical space using the outer surface of the skull for registration. A head phantom is constructed by placing a latex swim cap over a plastic skull and pouring a gelatin mixture into the space between skull and cap. A Panametrics 10.0 MHz immersion type ultrasound transducer has been rigidly attached to an optically tracked probe. This device is swept across the phantom to localize the surface of the skull. A standard deviation sliding filter is applied to the ultrasound signals to determine the location of the skull echoes. A CT derived model of the surface of the skull is generated using contours obtained from a deformable model-based segmentation algorithm. The CT and ultrasound surfaces are registered using a modified iterative closest point (ICP) algorithm. Results of a phantom experiment, validated with the Vanderbilt fiducial marker system, show target registration errors less than 4 mm. This result shows the feasibility of performing physical space to CT space registration using the outer surface of the skull.