Will SPIM kill the confocal?

I’ve been hearing more and more about SPIM systems, or “Light Sheet” microscopes. They rely on a simple change in the use of objectives, which provides one objective for excitation of an imaging plane, and another objective for collection of emission. This avoids the PSF error found in a conventional system, where the exciting and collecting objective are the same, resulting in excitation of non-focal areas. Compared to a traditional confocal, this design offers numerous advantages.

• Because the illumination plane is not provided by the collecting objective, the plane’s depth can be controlled. So you can image at, or below, the depth of field of the collecting lens.
• As no out of focus light is used for excitation, you don’t collect this noise in the emission image. While avoiding the out of focus light, you don’t have to exclude it subtractively like you do on a pinhole-based confocal, so you get a LOT more light throughput from the system.
• The design requires minimal hardware investment and can use lower power excitation light, dropping the cost of acquisition down to a very reasonable price.

As with everything new, I’d assume there will be numerous drawbacks that prevent this technique from being the “end all/be all” new technique. For instance even now it’s difficult to figure out how to mount specimens, how to orient the “microscope” as it’s not traditional, and how to maneuver the specimen so that motion appears the same as what we see on other scopes.

Over time, it’s possible that a solution like this may in fact eliminate the use of the pinhole for subtracting “bad” light. So will SPIM Kill the confocal? Well, sorry to say that’s a teaser title, and of course there’s no way to know! But, consider that confocal tech has been around for quite some time now, and it continues to be a low efficiency solution to the problem of haze. So who knows whether this will be the next big technique. I think it has the elements for success. It leverages currently available technology, lowers cost to produce a system, and does so without complicated post-processing. So I’d say this technique has the potential to replace confocal systems, but only time will tell. 🙂

-Austin