BiOS Hot Topics highlights photonics' move into clinical applications

San Francisco, CA--Every year, Laser Focus World and BioOptics World editors write about many of the latest biophotonic advances including optogenetics, photoacoustics, and multi-modality or hybrid imaging. While many of these disciplines are less than a decade old, the well-attended Saturday night 7-9 pm BiOS Hot Topics session at SPIE Photonics West (http://spie.org/photonics-west.xml) highlighted how these technologies are already making tremendous inroads into clinical applications--targeting neural diseases, cancer, and making surgery less invasive.

Optogenetics--the science of activating or silencing tissues and individual cells using light-activated channelrhodopsins--seemed like science fiction only a decade ago. But in his presentation "Optogenetics and Hybrid Optical Control of Cells," Ernst Bamberg from Germany's Max Planck Institute said that channelrhodopsin 2 (ChR2) is being used in more than 1000 labs worldwide for everything from nerve cell activation towards understanding how the brain is affected by physical body movements to ophthalmic substitution to allow blind animals--eventually humans--to see. While still in the R&D stage, optogenetics has blossomed into a mainstream analysis tool in the hands of thousands, rather than just a few research groups.

Another case in point of the rapid progression of photonics into the clinical biomedical arena is optical coherence tomography (OCT). In 2010, Ben Potsaid of the Massachusetts Institute of Technology (MIT) said in his presentation entitled "MEMS Tunable VCSEL Technology for High-Speed OCT" that 16 million ophthalmic OCT-based procedures had been completed in 2010. And while the current technology is impressive at some 26,000 axial scans per second, vertical-cavity surface-emitting laser (VCSEL) sources for OCT can achieve 50X faster scan rates: 1.2 MHz versus the standard 25 kHz OCT systems being used today. And what about the -25 dB image degradation for traditional OCT at 3 mm tissue depths? A VCSEL-based source can, says Potsaid, see at depths of 1.5 m at only 10 dB down. Rather than just seeing small section of tissue, the cornea, lens, and retina of the eye, for example, can all be seen together.

Dan Oron of the Weizmann Institute of Science in Israel discussed how temporal focusing allows imaging through scattering or turbid tissue, using correlated speckle patterns to see brain tissue at depths > 200 microns. And in a related talk from Bernard Choi at the Beckman Laser Institute on "Camera-Based Functional Imaging of Tissue Hemodynamics," speckle contrast imaging is being used in conjunction with spatial frequency domain imaging--a hybrid imaging or multi-modality setup--to image blood flow.

Real-time blood-flow imaging is extremely important to monitoring tissues during surgery, and has serious implications for "reduced surgical morbidity," which was the subject of another presentation from Jonathan Sorger of Intuitive Surgical who discussed clinical needs for robotic surgery. Although of the 240 million total surgeries performed last year only 500,000 were performed using robotic systems such as DaVinci, contrast that with just several thousand robotic surgeries only a few years ago. Without the imaging capabilities being developed by the photonics community, robotic surgery would not be progressing at its current astonishing pace.

Matthias Fink of Institute ESPCI, CNRS (France) explained how elasticity imaging (shear-wave imaging) can play a critical role in identifying benign vs. malignant tumors based on tissue stiffness, and Joe Culver of Washington University in St. Louis described "Functional Imaging of the Brain"--an attempt to correlate human brain mapping (functional MRI mapping) to an understandable mouse model to better map brain disease.

And the evening concluded with Vladimir Zharov of the University of Arkansas for Medical Sciences on how photoacoustic flow cytometry is gaining specificity to the level where individual cancer cells or other diseases could be identified in blood flows and zapped by a laser as they pass by. While it may sound decades away, the capability is being demonstrated today and a company has been formed--Cyto Wave Technologies--with an aim to develop "a first-in-class laser-based medical device that allows the in vivo detection and destruction of metastatic cancer cells." The capability would be groundbreaking and life-saving; far too many people are being taken from us due to cancer.

--Gail Overton

SOURCE:Laser Focus World; http://www.laserfocusworld.com