What if a microscope allowed us to explore the 3D microcosm of blood vessels, nerves and cancer cells instantly in virtual reality? What if it could provide views in multiple directions in real time without physically moving the sample and operated up to 100 times faster than current technology?
Scientists at UT Southwestern collaborated with colleagues in England and Australia to build and test a new optical device that converts commonly used microscopes into multi-angle projection imaging systems. The invention, described in an article of Natural methods, could open new avenues in advanced microscopy, according to the researchers.
“This is a completely new technology, although the theoretical underpinnings of it can be found in old computer literature,” says corresponding author Reto Fiolka, Ph.D. Him and co-author Kevin Dean, Ph .D., Are both Assistant Professors in Cell Biology and in the Lyda Hill Department of Bioinformatics at UT Southwestern.
“It’s like holding the biological sample with your hand, rotating it and inspecting it, which is an incredibly intuitive way to interact with a sample. By quickly imaging the sample from two different perspectives, we can view the sample interactively in virtual reality on the fly, ”says Dean, director of UTSW Microscopy Innovation Laboratory, which works with researchers across campus to develop custom instruments that take advantage of advances in optical microscopy.
Currently, acquiring 3D image information from a microscope requires a data-intensive process, in which hundreds of 2D images of the sample are assembled into what is called a stack of images. To visualize the data, the stack of images is then loaded into graphics software that performs calculations to form two-dimensional projections from different viewing perspectives on a computer screen, the researchers say.
“Both of these steps are very time consuming and can require a very powerful and expensive computer to interact with the data,” says Fiolka.
The team realized that they could form projections from multiple angles by optical means, without having to acquire stacks of images and render them with a computer. This is achieved by a simple and economical unit consisting of two rotating mirrors which is inserted in front of the camera of the microscope system.
“As a result, we can do all of this in real time, without any noticeable delay. Surprisingly, we can look at our samples from different angles ‘live’ without spinning the samples or the microscope,” says Fiolka. “We believe that this invention may represent a new paradigm for the acquisition of 3D information via a fluorescence microscope.”
It also promises blazingly fast imaging. While an entire stack of 3D images may require hundreds of camera images, the new method requires only one camera exposure.
Initially, researchers developed the system with two common light sheet microscopes that require a post-processing step to make sense of the data. This step is called misalignment and basically means rearranging the individual images to remove some distortion from the 3D image stack. Scientists originally sought to perform this rectification optically.
While experimenting with the optical straightening method, they realized that when they used the wrong amount of “misalignment”, the projected image appeared to rotate.
“That was the moment aha !. We realized that this might be more important than just an optical misalignment method; that the system might work for other types of microscopes as well,” Fiolka said.
“This study confirms that the concept is more general,” says Dean. “We have now applied it to a variety of microscopes, including confocal light sheet and spinning disc microscopy.”
Using the new method under a microscope, they imaged calcium ions carrying signals between nerve cells in a culture dish and examined the vascular system of a zebrafish embryo. They also quickly imaged moving cancer cells and a beating zebrafish heart.