Rationale and objectives

Real-time tomographic reflection (RTTR) permits in situ visualization of tomographic images so that natural hand-eye coordination can be used directly during invasive procedures. The method uses a half-silvered mirror to merge the visual outer surface of the patient with a simultaneous scan of the patient's interior without requiring a head-mounted display or tracking. A viewpoint-independent virtual image is reflected precisely into its actual location. When applied to ultrasound, we call the resulting RTTR device the sonic flashlight. We previously implemented the sonic flashlight using conventional two-dimensional ultrasound scanners that produce B-mode slices. Real-time three-dimensional (RT3D) ultrasound scanners recently have been developed that permit RTTR to be applied to slices with other orientations, including C-mode (parallel to the face of the transducer). Such slice orientation may offer advantages for image-guided intervention.

Materials and methods

Using a prototype scanner developed at Duke University (Durham, NC) with a matrix array that electronically steers an ultrasound beam at high speed in 3D, we implemented a sonic flashlight capable of displaying C-mode images in situ in real time.

Results

We present the first images from the C-mode sonic flashlight, showing bones in the hand and the cardiac ventricles.

Conclusion

The extension of RTTR to matrix array RT3D ultrasound offers the ability to visualize in situ slices other than the conventional B-mode slice, including C-mode slices parallel to the face of the transducer. This orientation may provide a broader target, facilitating certain interventional procedures. Future work is discussed, including display of slices with arbitrary orientation and use of a holographic optical element instead of a mirror.