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	Research Group Medical Image Processing

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Medical Image Processing

Ultrasound Bone Imaging

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•	Prof. Dr. Laurenz Wiskott
•	Prof. Dr. Gregor Schöner
Research groups
•	Theory of embodied cognition Prof. Dr. Gregor Schöner
•	Theory of Neural Systems Prof. Dr. Laurenz Wiskott
•	Neural Plasticity Lab PD Dr. Hubert Dinse
•	Real-Time Optical Imaging Lab Dr. Dirk Jancke
•	Organic Computing Dr. Rolf Würtz
•	Optimization of adaptive systems Jun.-Prof. Dr. Christian Igel
•	Autonomous robotics Dr. Ioannis Iossifidis
•	Medical Image Processing Dr. Susanne Winter
•	Real-time computer vision Jan Salmen
•	Multi-sensory fusion Dr. Andrey Bogdanov

Ultrasound Bone Imaging

Fig. 1: Axial ultrasound and corresponding CT slice of the lumbar spine

The disadvantage of bone imaging with ultrasound lies in the fact that, in contrast to CT or MR imaging, only few parts of the bone surface can be visualized (see Figure 1). Therefore, volume based registration algorithms cannot be used for bone registration. Existing approaches apply surface-surface registration methods after segmentation of bone surfaces in both ultrasound and CT images. However, the ultrasound surface segmentation is time consuming and not robust enough to be applied to real data, especially to data of the spine.
We developed a robust algorithm to register intraoperative three dimensional ultrasound data of the spine with preoperative CT data. Our approach based on surface-volume registration overcomes the abovementioned disadvantages by avoiding the segmentation of ultrasound data.

The tissue-bone interface produces a very strong signal in the ultrasound data. And because of the nearly total reflection at the tissue bone interface only the first bone surface reached by the ultrasound wave can be imaged. As the reflection at the bone surface is almost perfectly specular, it can be compared to a mirror for the ultrasound waves. Therefore the ultrasound sensor detects only surfaces which are nearly orthogonal to the direction of the ultrasound propagation (see figure 2).

Fig. 2: Sound reflection at bone surfaces

Fig. 3: Axial and sagittal ultrasound slices of a phantom with plastic vertebrae

patient

Fig. 4: Axial and sagittal ultrasound slices of a human lumbar spine

Research GroupMedical Image Processing

Ultrasound Bone Imaging

Research Group
Medical Image Processing