Optical and life scientists connect at OSA meeting

The Optical Society of America (OSA; Washington, DC) is seeking and finding more involvement with scientific and regulatory communities in the life sciences, according to Thomas Baer, president of Arcturus Engineering (Mountain View, CA) and cochair of the committee for the 1997 OSA meeting that was held in Long Beach, CA, last October.

Optical and life scientists connect at OSA meeting

Hassaun Jones-Bey

The Optical Society of America (OSA; Washington, DC) is seeking and finding more involvement with scientific and regulatory communities in the life sciences, according to Thomas Baer, president of Arcturus Engineering (Mountain View, CA) and cochair of the committee for the 1997 OSA meeting that was held in Long Beach, CA, last October.

The need for involvement is twofold. A great deal of optical technology developed for nonmedical applications could have a significant positive impact if applied to the life sciences. In addition, much of the work of optics researchers could take on more practical biomedical value if the researchers are better informed of the needs of people working in medicine and the life sciences.

Several people are already doing optics development in the biomedical area, Baer said. Their effectiveness could be enhanced by active OSA involvement with biomedical communities.

"There is a large community in regulatory areas, both at the US Food and Drug Administration (FDA) and at the Patent Office, that could benefit from greater exposure to what is really the state of the art in the optics area. So part of my agenda is to provide this opportunity," Baer said about the Focus on the Life Sciences in the 1997 meeting. He added that the communication needs to go both ways.

"The majority of the OSA community is relatively sheltered from what I consider to be major medical issues recognized by the medical community," he said. "There are certain exceptions, but, to a large extent, research here is done by and reported to the community within the OSA and not extensively outside."

In preparing for the meeting, Baer and cochair Mary Johnson of the University of Maryland (Baltimore, MD) asked technical groups in the society to come u¥with symposia related to the life-sciences theme. As a result, about 200 talks and 40 symposia (20% of the scientific program) had life-science components.

Interesting examples of life-science applications discussed included the use of rubber mirrors--originally developed for the Strategic Defense Initiative--to study and improve visual acuity in humans; the adaptation of multispectral imaging--originally developed for aerospace programs--to biomedical imaging problems; and the development of disposable optics for clinical uses, such as noninvasive glucose monitoring.

The OSA also made special efforts at this meeting to encourage participation by dermatologists who perform skin resurfacing and ophthalmologists who perform photorefractive keratectomy (PRK). Multidisciplinary symposia at the beginning of the meeting included FDA representatives, equipment manufacturers, physicians, and optical scientists all giving different perspectives on the pros and cons of PRK.

Spectral karyotyping

During a symposium on spectral imaging in the life sciences, Merryn Macville from the National Institutes of Health (NIH; Bethesda, MD) and Roland Eils from the University of Heidelberg (Heidelberg, Germany) gave the first two talks on multicolor fluorescence imaging of human chromosomes. Following was a talk during the same symposium on ultrafast laser research at the University of California-San Diego (UCSD) that may prove useful for biological studies.

Macville presented a spectral- karyotyping (SKY) technique that combines fluorescence microscopy, Fourier-transform interferometry, and CCD imaging to identify and examine chromosomes. The chromosomes are first "painted" using a fluorescence in situ hybridization (FISH) technique in which each target chromosome hybridizes with a corresponding probe chromosome labeled with a unique combination of fluorescent dyes. Finding 24 different fluorescent dyes would normally limit the ability of the FISH technique to mark all 24 human chromosomes.

Combinatorial labeling of the painting probes overcomes this limitation by requiring only five different fluorescent dyes that can be applied in any of 31 possible combinations. The SKY technique can then resolve the various frequency combinations after a single exposure on each chromosome through spectral imaging of all points in the sample simultaneously.

Applications for multicolor karyotyping, which offers improved accuracy over conventional approaches, include clinical applications such as predicting birth defects and studying cancer cells in tumors, as well as in experimental studies that either use animal models of human disease or make comparisons between species (see Fig. 1 on p. 15).

Researchers at the University of Heidelberg have developed a software-intensive version of the multicolor-karyotyping technique, which requires less human interaction for image acquisition and spectral calibration than the SKY system developed at the NIH, Eils said.

SKY uses Sagnac interferometry to build an interferogram that yields a continuous spectrum, while the Multiplex-FISH method developed at Heidelberg uses five gray-scale CCD images acquired through five fluorochrome-specific optical filters to create a spectral datastack. The software in the Multiplex-FISH method plays an important role in providing good spectral resolution.

A possibility for improving the resolution in both methods was raised during a presentation on two-photon confocal microscopy being performed with ultrafast lasers in the femtobiology program at UCSD. Jeff Squier, of UCSD, reported his group`s success, in cooperation with a team from the University of Amsterdam, in using 15-fs pulses to measure and compensate for dispersion characteristics in the entire series of objectives for microscopes manufactured by Zeiss (Oberkochen, Germany; see Fig. 2).

Measurement of dispersion at the microscope focus with ultrafast pulses allowed the researchers to determine precise spacing for a pair of fused-silica prisms to cancel the dispersive effects for each objective in the series. The results, which have been submitted for publication in the Journal of Microscopy, also apply to microscopy performed with broader pulses, according to Squier.

"People won`t necessarily image with 15-fs pulses," Squier said. "[But 15-fs pulses] provide a very sensitive way of characterizing the system."

A number of factors will have to be worked out before the UCSD work can actually be applied to the multicolor-fluorescence-imaging technique. Re searchers on both sides were intrigued by the possibilities, however. And Kevin Liddane of OptoSigma (Santa Ana, CA) has already begun preparations for a session on ultrafast-laser applications in the life sciences for the 1998 OSA meeting. "[Many people in the optics community] feel that there`s a significant contribution that can be made to advance biomedical applications, instrumentation, and techniques," said Liddane. "In putting everybody together in the same room, one of the things I hoped to accomplish was to give people working on the front lines of research--in genetics for example--a chance to teach the optical people what`s going on in genetics and perhaps to present some of the issues they would like to solve."

Total attendance of 2169 at the 1997 meeting exceeded the expected attendance figure of 1500 by more than a third. But it didn`t approach the unusually high attendance of 3200 at the 1996 meeting, which was held in Rochester, NY, and coincided with the 80th anniversary of the society.

Nobel winners announced

On the third day of the meeting, William Phillips of the National Institute of Standards and Technology (Gaithersburg, MD) was one of three researchers awarded the Nobel Prize in physics for work in laser cooling. Arthur Schawlow, who helped introduce the idea that light could be used to cool atoms in 1975 and who won a Nobel Prize in physics in 1981, shared the podium with Phillips and Robert Curl, who was awarded the Nobel Prize in chemistry in 1996.

Asked how he expected life to change after winning the Nobel Prize, Phillips said colleagues who had won it previously told him to expect to do a lot less laser science for a while and to talk about it a lot more. While giving more talks won`t directly advance his laboratory`s research, Phillips said the communications activities "are useful in their own right."

REFERENCE

1. E. Schröck et al., Science, 273, 494 (26 July 1996).

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