Application of Femtosecond Lasers in Confocal and Scanning Tunnelling Microscopy
Femtosecond lasers for sub-surface tissue cutting
description
Transcript of Femtosecond lasers for sub-surface tissue cutting
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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
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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
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Nonlinear absorption
transparentmaterial
100 fs
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Tight focusing of femtosecond pulses produces high intensity in the focal volume
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Nonlinear absorption
High intensity leads to nonlinear absorption
transparentmaterial
100 fs
objective
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Nonlinear absorption
Energy is deposited into a microscopic volume located in the bulk of the material
transparentmaterial
objective
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Nonlinear absorption
This energy deposition can lead to permanent structural changes in the bulk of the glass
transparentmaterial
objective
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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)
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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
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In vivo fluorescent angiography during cut
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In vivo fluorescent angiography during cut
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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
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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)
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Surface arteriole occlusion
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C. Schaffer, et al., PLoS Biology 4, e22 (2006)
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Flow change after surface arteriole occlusion
C. Schaffer, et al., PLoS Biology 4, e22 (2006)
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Single-cell surgery
Cutting the lateral dendrite in the Mauthner cell of a zebrafish
Collaboration with Joe Fetcho, Cornell Neurobiology
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Acknowledgments
Funding: Ellison Medical FoundationAmerican Heart Association American Society of Laser Medicine and SurgeryPhotonics Technologies Assistantship ProgramCornell Ithaca/Weill seed grant
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