Highlights of the LASER-TISSUE INTERACTIONS IX conference at the SPIE Biomedical Optics Society (BiOS) meeting at Photonics West, San Jose.

NewsEtc., March, 1998. Steven Jacques, Oregon Medical Laser Center

The 9th annual Laser-Tissue Interaction Conference was held at the Biomedical Optics Symposium of the SPIE Photonics West '98 meeting in San Jose, California, January 24-30, 1998. The conference was supported by a grant from the Air Force Office of Sponsored Research (AFOSR). Here is a quick summary of the meeting and some highlights.

Click here for the 3-day conference schedule

The conference began with a special session on immune responses to cancer following laser-tissue interactions, either photodynamic therapy or photothermal injury combined with a stimulatory adjuvant. The ability to recruit an immunological response following direct damage to cancer tissue by a laser therapy may prove to be an important mechanism of cancer treatment. The session was organized by Oklahoma School of Science and Mathematics and Univ. of Oklahoma.

My favorite talk of the conference was by Jay Walsh, Northwestern Univ., on flash photography with polarized light to visualize transient strain in collagen fibers of the cornea caused by an expanding/collapsing vapor bubble generated under water by a pulsed holmium:YAG laser.
Laser-induced straining of a biologic material analyzed using a polariscopic imaging technique, J. T. Walsh, Jr., Northwestern Univ.; G. P. Delacretaz, D. Beghuin, Ecole Polytechnique Federale de Lausanne (Switzerland) [3254-44]
They used 5-ns pulses of circularly polarized light for illumination to create freeze-action photographs of the birefringent collagen fibers of the cornea which captured the instantaneous distribution of strain in fibers. The photographs demonstrated the most intense strain occured during the bubble collapse.

On the theoretical front, reports by Los Alamos National Laboratory, Lawrence Livermore National Laboratory, and several others showed progress in the understanding of laser-induced mechanical effects in biomaterials. Of special note:

• Internal photomechanical fracture of spatially limited absorbers irradiated by short laser pulses, G. Paltauf and H.Schmidt-Kloiber, Karl-Franzens-University Graz (Austria) [3254-67]
  Once again, Guenther Paltauf and H. Schmidt-Kloiber presented compelling flash photography pictures of ns-pulse laser effects.
• Simulations of waves and cavitation bubbles produced in water by picosecond and nanosecond laser pulses, R. J. Scammon, E. J. Chapyak, R. P. Godwin, Los Alamos National Lab.; A. Vogel, Medizinisches Laserzentrum Luebeck (FRG) [3254-35]
  The agreement between theory and experiment continues to improve. The dynamics of bubble expansion and collapse are important for many pulsed laser applications when laser energy is delivered under water or within a saline flush.
• Two-dimensional vapor bubble simulations for medical applications, P. Amendt, D.S. Bailey, R.A. London, D. Maitland, Lawrence Livermore Natl. Lab.; M.Strauss, Nuclear Research Ctr. (Israel) [3254-XX]
  The Lawrence Livermore group continues to develop their 2-D hydrodynamic code LATIS for modeling LASer-TISsue interactions. Recent code improvements include accounting for multi-photon absorption and the effects of material strength and failure including rate hardening and dynamic melt effects.

Since 1993, the conference has been home for a group of investigators presenting reports on ocular effects of pulsed lasers. This year Sessions 6 and 7 were chaired by Pat Roach (AFOSR) and Bernard Gerstman (Florida International Univ.) and covered a variety of topics related to pulsed laser effects and mechanisms of eye injury.

Sorry all reports could not be mentioned here. The quality of papers was consistently high. A total of 48 papers were presented.