Effect of pulse duration on photomechanical response of soft tissue during ho:yag laser ablation

E. Duco Jansen; Massoud Motamedi; T. Joshua Pfefer; Thomas Asshauer; Martin Frenz; Guy Delacrétaz; George S. Abela; A. J. Welch

doi:10.1117/12.209071

Effect of pulse duration on photomechanical response of soft tissue during ho:yag laser ablation

E. Duco Jansen, Massoud Motamedi, T. Joshua Pfefer, Thomas Asshauer, Martin Frenz, Guy Delacrétaz, George S. Abela, A. J. Welch

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Abstract

Mechanical injury during pulsed holmium laser ablation of tissue is caused by rapid bubble expansion and collapse or by laser-induced pressure waves. In this study the effect of pulse duration on the photomechanical response of soft tissue during holmium:YAG laser ablation has been investigated. The dynamics of laser-induced bubble formation was documented in water and in transparent polyacrylamide tissue phantoms with a water concentration of 84 %. Holmium:YAG laser radiation (λ= 2.12 rim) was delivered in water or tissue phantoms via an optical fiber (200 or 400μm). The laser was operated in either the Q-switched mode ('ri, = 500 ns, Q_p = 14±1 mJ, 200 n fiber, H = 446 mJ/mm²) or the free-running mode (100-1100 s, Q = 200±5 mJ, 400 .im fiber, H = 1592 mJ/mm²). Bubble formation was documented using a fast flash photography setup while simultaneously a PVDP needle hydrophone (40 ns risetime), recorded pressures. The effect of the pulse duration on the photomechanical response of soft biological tissue was evaluated by delivering 5 pulses of 800 mJ to the intimal side of porcine aorta in vitro, followed by histologic evaluation. It was observed that, as the pulse duration was increased the bubble shape changed from almost spherical for Q-switched pulses to a more elongated, cylindrical shape for the longer pulse durations. The bubble expansion velocity was larger for shorter pulse durations. A thermo-elastic expansion wave was measured only during Q-switched pulse delivery. All pulses that induced bubble formation generated pressure waves upon collapse of the bubble in water as well as in the gel. The amplitude of the pressure wave depended strongly on the size and geometry of the laser-induced bubble. The important fmdings of this study were (1) the magnitude of collapse pressure wave decreased as laser pulse duration increased, and (2) mechanical tissue damage is reduced significantly by using longer pulse durations (> 460 is, for the pulse energy used).

Original language	English (US)
Pages (from-to)	459-465
Number of pages	7
Journal	Proceedings of SPIE - The International Society for Optical Engineering
Volume	2395
DOIs	https://doi.org/10.1117/12.209071
State	Published - May 12 1995
Event	Lasers in Surgery: Advanced Characterization, Therapeutics, and Systems V 1995 - San Jose, United States Duration: Feb 1 1995 → Feb 28 1995

Keywords

Ablation
Bubble Formation
Holmium Laser
Infrared
Photomechanical
Pressure
Pulse Duration
Tissue Damage

ASJC Scopus subject areas

Electronic, Optical and Magnetic Materials
Condensed Matter Physics
Computer Science Applications
Applied Mathematics
Electrical and Electronic Engineering

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10.1117/12.209071

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@article{c1a49294e2e247ad88187289f707a8cc,

title = "Effect of pulse duration on photomechanical response of soft tissue during ho:yag laser ablation",

abstract = "Mechanical injury during pulsed holmium laser ablation of tissue is caused by rapid bubble expansion and collapse or by laser-induced pressure waves. In this study the effect of pulse duration on the photomechanical response of soft tissue during holmium:YAG laser ablation has been investigated. The dynamics of laser-induced bubble formation was documented in water and in transparent polyacrylamide tissue phantoms with a water concentration of 84 %. Holmium:YAG laser radiation (λ= 2.12 rim) was delivered in water or tissue phantoms via an optical fiber (200 or 400μm). The laser was operated in either the Q-switched mode ('ri, = 500 ns, Qp = 14±1 mJ, 200 n fiber, H = 446 mJ/mm2) or the free-running mode (100-1100 s, Q = 200±5 mJ, 400 .im fiber, H = 1592 mJ/mm2). Bubble formation was documented using a fast flash photography setup while simultaneously a PVDP needle hydrophone (40 ns risetime), recorded pressures. The effect of the pulse duration on the photomechanical response of soft biological tissue was evaluated by delivering 5 pulses of 800 mJ to the intimal side of porcine aorta in vitro, followed by histologic evaluation. It was observed that, as the pulse duration was increased the bubble shape changed from almost spherical for Q-switched pulses to a more elongated, cylindrical shape for the longer pulse durations. The bubble expansion velocity was larger for shorter pulse durations. A thermo-elastic expansion wave was measured only during Q-switched pulse delivery. All pulses that induced bubble formation generated pressure waves upon collapse of the bubble in water as well as in the gel. The amplitude of the pressure wave depended strongly on the size and geometry of the laser-induced bubble. The important fmdings of this study were (1) the magnitude of collapse pressure wave decreased as laser pulse duration increased, and (2) mechanical tissue damage is reduced significantly by using longer pulse durations (> 460 is, for the pulse energy used).",

keywords = "Ablation, Bubble Formation, Holmium Laser, Infrared, Photomechanical, Pressure, Pulse Duration, Tissue Damage",

author = "Jansen, {E. Duco} and Massoud Motamedi and Pfefer, {T. Joshua} and Thomas Asshauer and Martin Frenz and Guy Delacr{\'e}taz and Abela, {George S.} and Welch, {A. J.}",

note = "Publisher Copyright: {\textcopyright} SPIE 1995. All rights reserved.; Lasers in Surgery: Advanced Characterization, Therapeutics, and Systems V 1995 ; Conference date: 01-02-1995 Through 28-02-1995",

year = "1995",

month = may,

day = "12",

doi = "10.1117/12.209071",

language = "English (US)",

volume = "2395",

pages = "459--465",

journal = "Proceedings of SPIE - The International Society for Optical Engineering",

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TY - JOUR

T1 - Effect of pulse duration on photomechanical response of soft tissue during ho:yag laser ablation

AU - Jansen, E. Duco

AU - Motamedi, Massoud

AU - Pfefer, T. Joshua

AU - Asshauer, Thomas

AU - Frenz, Martin

AU - Delacrétaz, Guy

AU - Abela, George S.

AU - Welch, A. J.

PY - 1995/5/12

Y1 - 1995/5/12

N2 - Mechanical injury during pulsed holmium laser ablation of tissue is caused by rapid bubble expansion and collapse or by laser-induced pressure waves. In this study the effect of pulse duration on the photomechanical response of soft tissue during holmium:YAG laser ablation has been investigated. The dynamics of laser-induced bubble formation was documented in water and in transparent polyacrylamide tissue phantoms with a water concentration of 84 %. Holmium:YAG laser radiation (λ= 2.12 rim) was delivered in water or tissue phantoms via an optical fiber (200 or 400μm). The laser was operated in either the Q-switched mode ('ri, = 500 ns, Qp = 14±1 mJ, 200 n fiber, H = 446 mJ/mm2) or the free-running mode (100-1100 s, Q = 200±5 mJ, 400 .im fiber, H = 1592 mJ/mm2). Bubble formation was documented using a fast flash photography setup while simultaneously a PVDP needle hydrophone (40 ns risetime), recorded pressures. The effect of the pulse duration on the photomechanical response of soft biological tissue was evaluated by delivering 5 pulses of 800 mJ to the intimal side of porcine aorta in vitro, followed by histologic evaluation. It was observed that, as the pulse duration was increased the bubble shape changed from almost spherical for Q-switched pulses to a more elongated, cylindrical shape for the longer pulse durations. The bubble expansion velocity was larger for shorter pulse durations. A thermo-elastic expansion wave was measured only during Q-switched pulse delivery. All pulses that induced bubble formation generated pressure waves upon collapse of the bubble in water as well as in the gel. The amplitude of the pressure wave depended strongly on the size and geometry of the laser-induced bubble. The important fmdings of this study were (1) the magnitude of collapse pressure wave decreased as laser pulse duration increased, and (2) mechanical tissue damage is reduced significantly by using longer pulse durations (> 460 is, for the pulse energy used).

AB - Mechanical injury during pulsed holmium laser ablation of tissue is caused by rapid bubble expansion and collapse or by laser-induced pressure waves. In this study the effect of pulse duration on the photomechanical response of soft tissue during holmium:YAG laser ablation has been investigated. The dynamics of laser-induced bubble formation was documented in water and in transparent polyacrylamide tissue phantoms with a water concentration of 84 %. Holmium:YAG laser radiation (λ= 2.12 rim) was delivered in water or tissue phantoms via an optical fiber (200 or 400μm). The laser was operated in either the Q-switched mode ('ri, = 500 ns, Qp = 14±1 mJ, 200 n fiber, H = 446 mJ/mm2) or the free-running mode (100-1100 s, Q = 200±5 mJ, 400 .im fiber, H = 1592 mJ/mm2). Bubble formation was documented using a fast flash photography setup while simultaneously a PVDP needle hydrophone (40 ns risetime), recorded pressures. The effect of the pulse duration on the photomechanical response of soft biological tissue was evaluated by delivering 5 pulses of 800 mJ to the intimal side of porcine aorta in vitro, followed by histologic evaluation. It was observed that, as the pulse duration was increased the bubble shape changed from almost spherical for Q-switched pulses to a more elongated, cylindrical shape for the longer pulse durations. The bubble expansion velocity was larger for shorter pulse durations. A thermo-elastic expansion wave was measured only during Q-switched pulse delivery. All pulses that induced bubble formation generated pressure waves upon collapse of the bubble in water as well as in the gel. The amplitude of the pressure wave depended strongly on the size and geometry of the laser-induced bubble. The important fmdings of this study were (1) the magnitude of collapse pressure wave decreased as laser pulse duration increased, and (2) mechanical tissue damage is reduced significantly by using longer pulse durations (> 460 is, for the pulse energy used).

KW - Ablation

KW - Bubble Formation

KW - Holmium Laser

KW - Infrared

KW - Photomechanical

KW - Pressure

KW - Pulse Duration

KW - Tissue Damage

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DO - 10.1117/12.209071

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VL - 2395

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EP - 465

JO - Proceedings of SPIE - The International Society for Optical Engineering

JF - Proceedings of SPIE - The International Society for Optical Engineering

T2 - Lasers in Surgery: Advanced Characterization, Therapeutics, and Systems V 1995

Y2 - 1 February 1995 through 28 February 1995

ER -

Effect of pulse duration on photomechanical response of soft tissue during ho:yag laser ablation

Abstract

Keywords

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