Method for Determining Bone Surface Points Using A-Mode Ultrasound

An A-mode ultrasound transducer is tracked in three-dimensions by an optical position tracking system as the transducer is scanned over the skin to generate measurements of bone surface distance from the transducer. A processor correlates the ultrasound data with position and orientation data to generate a three-dimensional physical space model of the bone surface which is registered with an image space model of the bone surface generated from a tomographic image to produce an alignment of the two models. The ultrasound transducer is replaced by an instrument which is also optically tracked. The alignment is used to translate instrument position in physical space to a position in image space for generation on a monitor of a composite display of the instrument and the tomographic image. This composite display can be used to guide positioning and orienting the instrument in physical space with respect to sites of interest observed in the tomographic image on the display.

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U.S. Patent # 6,106,464: Apparatus and method for bone surface-based registration of physical space with tomographic images and for guiding an instrument relative to anatomical sites in the image