"Sonic Flashlight" Makes Human Body Appear Translucent

Originally Published MDDI January 2002R&D DIGEST"Sonic Flashlight" Makes Human Body Appear Translucent

January 1, 2002

3 Min Read
"Sonic Flashlight" Makes Human Body Appear Translucent

Originally Published MDDI January 2002


"Sonic Flashlight" Makes Human Body Appear Translucent

The technique used in the "sonic flashlight" uses a tanslucent mirror to merge an ultrasound-based image with the physician's view of the patient. Photo courtesy of George Stetten.(click to enlarge)

Physicians have continued to use traditional film or screen images to assess the condition of a patient. For example, invasive procedures such as needle biopsies are guided by ultrasound images. Because the doctor must look away from the patient at a display screen, his or her hand-eye coordination can be affected. Now, a prototype device developed by a biomedical engineer at the University of Pittsburgh enables a physician to remain focused on the patient during an ultrasound-guided procedure. Called a "sonic flashlight," the device makes the human body seem translucent, says George Stetten, MD, PhD, assistant professor of bioengineering at the university and a research scientist at the Carnegie Mellon University Robotics Institute.

The view provided by the device essentially combines the visual outer surface of a patient's skin with a real-time ultrasound scan of the tissues within. The result is a 3-D translucent ultrasound image of blood vessels, muscle tissue, and other structures that appears to float in its actual location within the patient.

There have been previous attempts to combine ultrasound and x-ray images with a physician's direct view of a patient. Most have been quite complex or limited by the amount of additional hardware the physician had to contend with, such as head-mounted video cameras. Other approaches, while similar to Stetten's, required the use a tracking device to monitor the viewer's location.

The biomedical engineer claims that his method eliminates the need for tracking devices and transmitters. Stetten explains that the system functions much like the way a translucent mirror superimposes images from opposite sides of the glass.

In Stetten's sonic flashlight, an ultrasound scanner and the ultrasound display are positioned on opposite sides of a half-silvered, translucent mirror. The patient and the ultrasound scanner positioned on the patient's skin can be viewed through the mirror. The ultrasound image is simultaneously projected on the viewer's side of the mirror in alignment with the corresponding location within the patient's body. This makes the ultrasound image appear to occupy the same physical space as the body part that is being imaged. The system enables the combined view to remain accurate as the viewing angle is changed.

The researcher calls the process "tomographic reflection," and explains that the method relies on maintaining the precise geometric relationships between the ultrasound slice being scanned, the monitor displaying the slice, and the mirror. "We are actually merging the virtual image in 3-D with the interior of the patient," Stetten says. "The reflected image is optically indistinguishable from the corresponding space within the patient."

The resulting image appears within the natural field of view. This enables the physician to perform such invasive procedures as amniocentesis, catheterization, or minimally invasive surgery while looking directly at the patient and not looking away toward a monitor.

Stetten has also built a prototype of a portable sonic flashlight that would be suitable for routine use in a physician's office. He explains that both the stationary and portable devices will need to be refined and tested in the laboratory before being tested in a clinical setting, however. Stetten received a research grant from The Whitaker Foundation for the project in 1994.

Copyright ©2002 Medical Device & Diagnostic Industry

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