http://www.bme.cornell.edu/schafferlab

Femtosecond lasers for sub-surface tissue cutting

Chris B. Schaffer

http://www.bme.cornell.edu/schafferlab

Message

• Using a tightly-focused femtosecond laser, it is possible to produce an micrometer-scale incision in the bulk of a tissue without affecting the overlying surface

http://www.bme.cornell.edu/schafferlab

How sharp is our scalpel?

• Minimum cut size is smaller than a single cell

• Maximal depth is around 1 mm

• Cut rates could be around 1 cm/s

http://www.bme.cornell.edu/schafferlab

Nonlinear absorption

transparentmaterial

100 fs

objective

Tight focusing of femtosecond pulses produces high intensity in the focal volume

http://www.bme.cornell.edu/schafferlab

Nonlinear absorption

High intensity leads to nonlinear absorption

transparentmaterial

100 fs

objective

http://www.bme.cornell.edu/schafferlab

Nonlinear absorption

Energy is deposited into a microscopic volume located in the bulk of the material

transparentmaterial

objective

http://www.bme.cornell.edu/schafferlab

Nonlinear absorption

This energy deposition can lead to permanent structural changes in the bulk of the glass

transparentmaterial

objective

http://www.bme.cornell.edu/schafferlab

Can even cut inside a piece of glass

Sub-surface damage in a glass sample

C. B. Schaffer, et al., Appl. Phys. Lett 84, 1441 (2004)

http://www.bme.cornell.edu/schafferlab

In vivo cortical cutting

• Urethane anesthetized rat with craniotomy for optical access to the brain

• Intravenous injection of fluorescent dye with two-photon excited fluorescence microscopy to visualize vasculature

• Translate animal at 10 µm/s while irradiating with – 1-kHz train of 0.5 to 7-µJ energy, 50-fs duration, 800-nm

wavelength laser pulses

– Focused at 0.95 NA at multiple depths between 100 and 700 µm beneath the brain surface.

• Collaborative work with Ted Schwartz, Weill Cornell, Neurological Surgery

http://www.bme.cornell.edu/schafferlab

In vivo fluorescent angiography during cut

http://www.bme.cornell.edu/schafferlab

In vivo fluorescent angiography during cut

QuickTime™ and a decompressor

are needed to see this picture.

http://www.bme.cornell.edu/schafferlab

Post-mortem of cut

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Post-mortem of cut

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Demonstrated capabilities and limits

• Cuts up to 700 µm deep achievable in brain– We’ll likely reach the 1.1-mm theoretical limit (in brain)

• Cuts size ranges from sub-micrometer to 10’s of micrometers, depending on laser energy

• It is difficult to cut directly underneath large blood vessels

http://www.bme.cornell.edu/schafferlab

Microvascular lesioningHemorrhage

Intravascular clot

50 µm

Extravasation

Can selectively target any vesselwithin the top 0.7 mm of cortex

C. Schaffer, et al., PLoS Biology 4, e22 (2006)N. Nishimura, et al., Nature Methods 3, 99 (2006)

http://www.bme.cornell.edu/schafferlab

Surface arteriole occlusion

QuickTime™ and a decompressor

are needed to see this picture.

C. Schaffer, et al., PLoS Biology 4, e22 (2006)

http://www.bme.cornell.edu/schafferlab

Flow change after surface arteriole occlusion

C. Schaffer, et al., PLoS Biology 4, e22 (2006)

http://www.bme.cornell.edu/schafferlab

Single-cell surgery

Cutting the lateral dendrite in the Mauthner cell of a zebrafish

Collaboration with Joe Fetcho, Cornell Neurobiology

http://www.bme.cornell.edu/schafferlab

Acknowledgments

Funding: Ellison Medical FoundationAmerican Heart Association American Society of Laser Medicine and SurgeryPhotonics Technologies Assistantship ProgramCornell Ithaca/Weill seed grant

http://www.bme.cornell.edu/schafferlab