One of the main problems with laparoscopic surgery is that the images offer no sense of depth, which can confuse novice surgeons and makes instrument placement more difficult. With 3D imaging, however, it is possible to overcome this problem. Modifications of old technologies, as well as the recent development of some new ones, have made 3D easier than ever to use, and we expect it will become increasingly common in minimally invasive procedures.

In real life, depth results from binocular vision: the two eyes see objects at slightly different angles, and the brain then triangulates object distances. 3D visualization systems simulate this experience by separating two cameras by a fixed distance, then presenting their outputs to each eye separately.

There are several different methods for presenting 3D information to the eyes. The most obvious is to use goggles or some other head-mounted device with separate LCD panels in front of each eye, as in the Viking 3Di Vision System. Although this provides an effective 3D image, the headset may become cumbersome over time, and the screens must be flipped up or removed to look around the operating room.

The da Vinci robot-assisted surgery system is based on a similar principle: inside the console are two high-fidelity analog monitors, with a mirror prism between them that deflects their images to binocular stereoscopes. Although this setup also offers an excellent 3D image, no other members of the team can see it. Moreover, this kind of setup is not possible for non-robot cases in which the surgeon is standing.

An alternative is to connect the two video sources to two different projectors, and to fit the projectors with lenses that polarize light at right angles to each other. The projected images are then overlapped on a screen, and the surgeon views them using glasses with similarly polarized lenses, such that each blocks the light destined for the other eye. The TrueVision Systems line of 3D visualization equipment, for example, is based on this setup. A major shortcoming, however, is that several large projection apparatuses may be required for the different members of the team, each of which consumes significant OR real estate. Moreover, the separation of information into left and right is imperfect, resulting in ghosting effects that may cause headache with prolonged viewing.

A variation on the polarization method known as Infitec is available from D’Ambra Systems and is claimed to provide better left-right separation, which would reduce the incidence of headache during long or back-to-back procedures. The basic set-up of two projectors with overlapping images is the same, but instead of simply polarizing the light sources, their system uses more complex filters on the projectors that cause each to represent individual colors as slightly different red-green-blue triplets. The viewer wears passive glasses with lenses that filter out the color triplets destined for the other eye. (For a helpful diagram that explains this principle, click here.) This technology is still relatively new, so the jury is still out as to how much of an improvement it offers over traditional polarization schemes, but the idea is promising.

In yet another method, a single television screen receives both video signals and presents them in extremely rapid alternation (about 120 Hz, so that each individual signal is presented at 60 Hz). The person viewing this screen wears glasses with LCD-containing lenses that black out in sync with the television — such that when the “left eye” video is onscreen, the glasses’ right eye is blacked out, and vice versa. Because the switching happens so quickly, the viewer’s brain is tricked into believing that the eyes are seeing two different but continuous images, which then fuse to form a three-dimensional perception. The only problem with this method is that when the surgeon looks at something besides the television screen, the lens flicker becomes noticeable and may cause headache.

Different solutions work for different situations, and choosing between these options requires a careful evaluation of your needs and budget. Things to consider include: how much physical space do you have for new hardware? how many people need to view the image in 3D? how long are the cases you’ll be doing in 3D?

For our money, we prefer shutter lenses, as 3D-capable flatscreens can also be used for standard, non-3D image presentation. In addition, anyone in the operating room can pick up a pair of glasses and see the image in 3D, which should enhance teaching and team coordination. Although the latter point is also true of projected images, the sheer size of projection apparatuses makes it impossible to have several of them in one room; thus, if you and an assistant are facing each other, one of you will be unable to see anything, unless both of you want to constantly turn your heads. With that said, there is no perfect solution yet, and the potential buyer is advised to try each before making a purchase.

(Many thanks to David Kaplan, of D’Ambra Technologies, for supplying helpful information about the various 3D systems described here.)