Tomographic reflection combines visual and ultrasound images

JANUARY 18--George Stetten, assistant professor of bioengineering at the University of Pittsburgh and the Carnegie Mellon Robotics Institute (Pittsburgh, PA; www.stetten.com/george/rttr), has developed a method that combines visual images with ultrasound images to aid in invasive surgical procedures such as tissue biopsy.

JANUARY 18--George Stetten, assistant professor of bioengineering at the University of Pittsburgh and the Carnegie Mellon Robotics Institute (Pittsburgh, PA; www.stetten.com/george/rttr), has developed a method that combines visual images with ultrasound images to aid in invasive surgical procedures such as tissue biopsy. In performing such procedures, physicians must look away from the patient to view the guiding ultrasound images. Such indirect hand-eye coordination systems can limit the physician's ability to easily find specific areas of interest without damaging the surrounding critical structures.

Called tomographic reflection, the process merges the visual outer surface image of the patient with a simultaneous ultrasound scan of the patient's interior. This resultant image allows the physician to visualize the skin and underlying tissues as if they were translucent. As a result, the physician no longer has to look away from the patient to see associated ultrasound images because they now appear merged with the outer skin of the patient.

Stetten developed both an immobile stationary prototype system and a portable hand-held device that he calls the Sonic Flashlight, which uses a 12 x 9-in. half-silvered mirror that bisects the angle between the ultrasound slice and a flat-panel monitor. Points in the ultrasound slice and their corresponding locations on the monitor are equidistant from the half-silvered mirror along a line perpendicular to the mirror distance. And, because the angle of incidence equals the angle of reflectance, the surgeon sees each point in the reflection at its corresponding physical location.

After images are captured with an ultrasound machine from Pie Medical (Indianapolis, IN), they are digitized using a PC-based video-capture board from Matrox (Dorval, Quebec, Canada) and displayed on a flat-panel monitor made by Pixtech (Santa Clara, CA). According to Stetten, these devices can capture and display images at 30 frames/s.

For more information, see Vision Systems Design, January 2002.

More in Life Sciences