Myocardium tissue ablation with high-peak-power nanosecond 1,064- and 532-nm pulsed lasers: Influence of laser-induced plasma

Makoto Ogura, Shunichi Sato, Miya Ishihara, Satoko Kawauchi, Tunenori Arai, Takemi Matsui, Akira Kurita, Makoto Kikuchi, Hiroshi Ashida, Minoru Obara

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Abstract

Background and Objectives: We investigated the mechanism and characteristics of porcine myocardium tissue ablation in vitro with nanosecond 1,064- and 532-nm pulsed lasers at laser intensities up to ≈5.0 GW/cm2. Particular attention was paid to study the influence of the laser-induced plasma on the ablation characteristics. The applicability of these two lasers to transmyocardial laser revascularization (TMLR) was discussed. Study Design/Materials and Methods: Porcine myocardium tissue samples were irradiated with 1,064- and 532-nm, Q-switched Nd:YAG laser pulses, and the ablation depths were measured. The temporal profiles of the laser-induced optical emissions were measured with a biplanar phototube. For the ablated tissue samples, histological analysis was performed with an optical microscope and a polarization microscope. Results: The ablation efficiency at 1,064 nm was higher than that at 532 nm. The ablation threshold at 1,064 nm (≈0.8 GW/cm2) was lower than that at 532 nm (≈1.6 GW/ cm2), in spite of the lower absorption coefficient being expected at 1,064 nm. For the 1,064-nm laser-ablated tissues, thermal damage was very limited, while damage presumably caused by the mechanical effect was observed in most of the cases. For the 1,064-nm laser ablation, the ablation threshold was equal to the threshold of the laser-induced optical emission (≈0.8 GW/cm2), while for the 532-nm laser ablation, the optical emission threshold (≈2.4 GW/cm2) was higher than the ablation threshold. Conclusions: We considered that for the 1,064-nm laser ablation, the tissue removal was achieved through a photodisruption process at laser intensities of > ≈0.8 GW/cm2. At laser intensities of > 3.0 GW/cm2, however, the ablation efficiency decreased; this can be attributed to the absorption of incoming laser pulses by the plasma. For the 532-nm laser ablation, the tissue removal was achieved through a photothermal process at laser intensities of > ≈1.6 GW/ cm2. At laser intensities of > 2.4 GW/cm2, a photodisruption process may also contribute to the tissue removal, in addition to a photothermal process. With regard to the ablation rates, the 1,064-nm laser was more suitable for TMLR than the 532-nm laser. We concluded that the 1,064-nm Q-switched Nd:YAG laser would be a potential candidate for a laser source for TMLR because of possible fiber-based beam delivery, its compact structure, cost effectiveness, and easy maintenance. Animal trials, however, have to be carried out to evaluate the influence of the tissue damage.

Original languageEnglish
Pages (from-to)136-141
Number of pages6
JournalLasers in Surgery and Medicine
Volume31
Issue number2
DOIs
Publication statusPublished - 2002 Sep 17

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Keywords

  • Laser-induced plasma
  • Mechanical damage
  • Photodisruption
  • Porcine myocardium
  • Q-switched Nd:YAG laser
  • Transmyocardial laser revascularization (TMLR)

ASJC Scopus subject areas

  • Surgery
  • Dermatology

Cite this

Ogura, M., Sato, S., Ishihara, M., Kawauchi, S., Arai, T., Matsui, T., Kurita, A., Kikuchi, M., Ashida, H., & Obara, M. (2002). Myocardium tissue ablation with high-peak-power nanosecond 1,064- and 532-nm pulsed lasers: Influence of laser-induced plasma. Lasers in Surgery and Medicine, 31(2), 136-141. https://doi.org/10.1002/lsm.10081