ITHACA, N.Y., June 12 -- A new imaging technique that could lead to optical biopsies without removal of tissue is being reported by biophysical scientists at Cornell and Harvard universities. The advance in biomedical imaging enables noninvasive microscopy scans through the surface of intact organs or body systems. Demonstrations of the new technique are producing images of diseased tissue at the cellular level with unprecedented detail, according to a Cornell statement.
Diagnoses of cancers and neurodegenerative diseases, such as Alzheimer's disease, are two applications suggested by the researchers in their report in Proceedings of the National Academy of Sciences (PNAS, June 10, 2003), "Live tissue intrinsic emission microscopy using multiphoton-excited native fluorescence and second harmonic generation." The researchers predict it should be possible to obtain endoscopic and laparoscopic images of tissues at the cellular level from deep within living animals, or even human patients, thus enabling a new form of optical biopsy.
The new imaging technique takes advantage of a Cornell-patented fluorescence emission microscopy system and the natural fluorescence of certain bodily constituents. The Cornell-Harvard team incorporated a technology into the new imaging procedure called multiphoton microscopy, invented in 1989 by Watt W. Webb an engineering and applied physics professor at Cornell, and Winfried Denk, now director of the The Max Planck Institute in Germany.
Multiphoton microscopy produces high-resolution, 3-D pictures of tissues with minimal damage to living cells, using a laser that produces a stream of extremely short, intense pulses, increasing the probability that two or three interact with an individual biological molecule at the same time. "This cumulative effect is the equivalent of delivering one photon with twice the energy (or half the wavelength) in the case of two-photon excitation, or three times the energy (one-third the wavelength) in three-photon excitation," Webb said.
The scanning laser microscope moves the focused beam of pulsed photons across a sample at a precise depth (plane of focus) so that cells above or below the plane are not affected, according to Webb. When repeated scans at different focal planes are "stacked," a 3-D picture emerges.
For more information, visit: www.drbio.cornell.edu/drbio.html