Myocardium tissue ablation with high-peak-power nanosecond 1,064- and 532-nm pulsed lasers: Influence of laser-induced plasma
✍ Scribed by Makoto Ogura; Shunichi Sato; Miya Ishihara; Satoko Kawauchi; Tunenori Arai; Takemi Matsui; Akira Kurita; Makoto Kikuchi; Hiroshi Ashida; Minoru Obara
- Publisher
- John Wiley and Sons
- Year
- 2002
- Tongue
- English
- Weight
- 377 KB
- Volume
- 31
- Category
- Article
- ISSN
- 0196-8092
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✦ Synopsis
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 approximately 5.0 gw/cm(2). 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 (approximately 0.8 gw/cm(2)) was lower than that at 532 nm (approximately 1.6 gw/cm(2)), 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 (approximately 0.8 gw/cm(2)), while for the 532-nm laser ablation, the optical emission threshold ( approximately 2.4 gw/cm(2)) 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 > approximately 0.8 gw/cm(2). at laser intensities of > 3.0 gw/cm(2), 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 > approximately 1.6 gw/cm(2). at laser intensities of > 2.4 gw/cm(2), 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.