Mitigating thermal mechanical damage potential during two-photon dermal imaging

Barry R. Masters; Peter T. C. So; Christof Buehler; Nicholas P. Barry; Jason D. B. Sutin; William W. Mantulin; Enrico Gratton

doi:10.1117/1.1806135

1 November 2004 Mitigating thermal mechanical damage potential during two-photon dermal imaging

Barry R. Masters, Peter T. C. So, Christof Buehler, Nicholas P. Barry, Jason D. B. Sutin, William W. Mantulin, Enrico Gratton

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Journal of Biomedical Optics, Vol. 9, Issue 6, (November 2004). https://doi.org/10.1117/1.1806135

Abstract

Two-photon excitation fluorescence microscopy allows in vivo high-resolution imaging of human skin structure and biochemistry with a penetration depth over 100 μm. The major damage mechanism during two-photon skin imaging is associated with the formation of cavitation at the epidermal-dermal junction, which results in thermal mechanical damage of the tissue. In this report, we verify that this damage mechanism is of thermal origin and is associated with one-photon absorption of infrared excitation light by melanin granules present in the epidermal-dermal junction. The thermal mechanical damage threshold for selected Caucasian skin specimens from a skin bank as a function of laser pulse energy and repetition rate has been determined. The experimentally established thermal mechanical damage threshold is consistent with a simple heat diffusion model for skin under femtosecond pulse laser illumination. Minimizing thermal mechanical damage is vital for the potential use of two-photon imaging in noninvasive optical biopsy of human skin in vivo. We describe a technique to mitigate specimen thermal mechanical damage based on the use of a laser pulse picker that reduces the laser repetition rate by selecting a fraction of pulses from a laser pulse train. Since the laser pulse picker decreases laser average power while maintaining laser pulse peak power, thermal mechanical damage can be minimized while two-photon fluorescence excitation efficiency is maximized.

©(2004) Society of Photo-Optical Instrumentation Engineers (SPIE)

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Barry R. Masters, Peter T. C. So, Christof Buehler, Nicholas P. Barry, Jason D. B. Sutin, William W. Mantulin, and Enrico Gratton "Mitigating thermal mechanical damage potential during two-photon dermal imaging," Journal of Biomedical Optics 9(6), (1 November 2004). https://doi.org/10.1117/1.1806135

Published: 1 November 2004

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