Stereoscopic Glasses Help Pediatric Cardiac Surgeons See Better

Researchers at Children's Hospital Boston (MA, USA) had already been testing a three-dimensional (3D) ultrasound imaging system. But although the images are 3D and are displayed in real time, they give little indication of depth. In animal tests, surgeons trying to navigate surgical tools inside the heart became disoriented when guided by these images. The researchers then realized that what they needed was stereoscopic vision.

With the collaboration of a researcher from Harvard University (Boston, MA, USA) the researchers adapted a ready-made solution used in video games - splitting computer images in two and tilting them at slightly different angles. The real-time stereoscopic visualization system was designed to handle and render 30 MB of data every second. The data is streamed in real time from an ultrasound system to a graphics station computer, which renders left-eye and right-eye views by alternating the position and orientation of the image. The rendered volumes, immediately displayed on a conventional monitor, are concomitantly synchronized with flickering shutter glasses worn by the surgeon, yielding stereo-rendered 3D ultrasound images. This imaging technology provides surgeons with significantly better spatial information and depth perception for making repairs inside the beating heart. When wearing the stereoscopic shutter glasses, the users are able to see the ultrasound images of the beating heart as a hologram.

To test the system, the researchers then created a 6-mm atrial septal defect (ASD) in 6 pigs using 3D echocardiography guidance. The defect was then closed using the glasses and using a catheter-based patch delivery system, which was attached with tissue mini-anchors threaded into the heart through a vein. In all, the researchers placed 64 anchors: 32 under standard 3D ultrasound guidance, and 32 using the stereoscopic vision display. The mean time of the anchor deployment for stereoscopic vision display group was shorter by 44% compared with the standard display group. Trajectory tracking of the anchor deployment device tip demonstrated greater navigational accuracy measured by trajectory deviation, and the accuracy of anchor placement was not significantly different. The study was published in the June 2008 issue of the Journal of Thoracic and Cardiovascular Surgery.

"You definitely have depth perception. You feel like you're inside the heart chamber,” said co-investigator Nikolay Vasilyev, M.D., of the department of cardiac surgery. "Clinical trials of beating-heart surgery with the patching system could begin in children with ASDs this year.”

The researchers believe that stereoscopic imaging, coupled with recent advances in catheter-based surgical tools, will eventually allow surgeons to do much more complex operations on beating hearts. For children, being able to do beating-heart surgery avoids large incisions that can scar the heart and disrupt its rhythm, thus avoiding the potential need for a pacemaker. Opening the heart also invites infection, and air bubbles and emboli can enter into the bloodstream and damage the brain. Running blood through a bypass machine can also sometimes launch an inflammatory response, damaging organs throughout the body. And even in uncomplicated open-heart surgeries, recovery times are often weeks to months.


Related Links:
Children's Hospital Boston
Harvard University