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Laser Ablation Tomography – Natural History’s “Hot” New Imaging Technique

Wheel Bug attacking a Wasp (LAT by L4IS)
Wheel Bug attacking a Wasp (Laser Ablation Tomogram by L4IS)

Imagine for a moment that you were given access to a nanosecond, Q-switched, ultraviolet laser; a servo-driven sample stage; a high resolution microscope-mounted CCD camera with a theoretical resolving power of 800 nm per pixel; and a collection of powerful computers loaded with advanced image collection and rendering software.  What would you do with it all?  Well, if you’re Benjamin Hall of Lasers for Innovative Solutions, then you use your newly acquired powers for the benefit of mankind and develop a new imaging technique.

Frustrated by the laborious, tedious, and often inadequate or otherwise inefficient capabilities of X-Ray, CT scanning, and MRI, Hall set to work developing a way to use ultrafast lasers and high resolution imaging to produce a cross-sectioning method that is orders of magnitude faster than traditional hand-sectioning.

Boll Weevil cross section (Laser Ablation Tomogram by L4IS)
Boll Weevil cross section (Laser Ablation Tomogram by L4IS)

The process involves placing a sample, such as a frozen yellow jacket (Vespinae), on a servo-driven stage and then subjecting it to a series of laser pulses that gradually ablate (i.e. “blast away) the tissue (or other material) layer by miniscule layer.  This generates a set of cross sections which are each recorded by the camera and then rendered into a tomogram post-process.  All this requires A LOT of computing power and storage.  For instance, according to Laser Focus World,

Imaged at a resolution of 5184 × 3456 pixels per slice, 1500 slices of a yellow-jacket stinger at 5 seconds of ablation per slice (and using a 160 μJ fluence level at a 28 kHz repetition rate) produced 27 billion voxels of data. To handle that amount of data, the use of a powerful video card, GPU processing, and significant subsampling are required to create digital models. Acquiring the data in full resolution allows for focusing in on particular features in high resolution using Visualization Sciences Group’s (Burlington, MA) Avizo Fire software.

Tip of a Fir Tree Branch (Laser Ablation Tomogram by L4IS)
Tip of a Fir Tree Branch (Laser Ablation Tomogram by L4IS)

The results of all this effort and computing is nothing shy of spectacular.  Once the images are assembled and rendered into 3D representations, you can literally see what it would be like to take a dive down the vessels in an apple tree root, see the precise arrangement of the organs and structures within a yellow jacket abdomen, or even capture the intricate internal aspects of a wheel bug attacking a wasp!  It’s a level of detail and insight that has wide-reaching applications for the natural sciences and for digital collections.  Botanists, entomologists, geologists, etc can all benefit from this technique and I can’t wait to see more (particularly when femtosecond lasers are employed which will minimize heat transfer to the areas around the ablated material.)

In the meantime, check out the videos below courtesy of Lasers for Innovative Solutions:

Further Reading:
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2 thoughts on “Laser Ablation Tomography – Natural History’s “Hot” New Imaging Technique Leave a comment

  1. Hi Mark. Thanks a lot for highlighting our technology. We are excited to see that our efforts to create a new 3 dimensional imaging technique are beginning to pick up some traction with the general public.

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    • You’re most welcome. It’s a fantastic technique and I’m very excited to see where it goes. Keep up the good work!

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