Hielscher Builds Optical Tomography System

Associate Professor Andreas Hielscher of the Department of Biomedical Engineering has received a grant from the National Cancer Institute at the National Institutes of Health to build an optical tomographic imaging system. The grant will fund research to develop image reconstruction algorithms and instrumentation for tomographic imaging of green fluorescent proteins (GFP) in small animals. The approximately $1.5 million grant is for four years.
Columbia holds the main patent on the use of GFP, an imaging marker developed by Prof. Martin Chalfie, Chair of the Biological Sciences Department. Using GFP and its derivatives, it is now possible to visualize nearly any protein of interest in any cell, tissue, or species. Researchers working at all levels of biology and medicine, such as single-molecule dynamics, protein trafficking within cells, organelle dynamics, and cell and tissue behaviors during development, cancer progression, and other diseases, are nowadays making use of GFP. 
Until now, tomographic imaging has relied on the diffusion model of light propagation in tissue. This has limited its application to studies involving fluorophores that emit in the near-infrared range, where tissue absorption is smaller than in the visible spectrum. By extending the optical tomographic methods to shorter wavelengths, there would be a way to image GFPs, which emit light in the visible spectrum.

Developing an optical tomography system for in vivo GFP imaging will have a significant impact on many areas of biomedical research. In this particular project, Professor Hielscher and his collaborators, Assistant Professor Alexander Klose of the Department of Radiology, and Professor Ronald Blasberg, M.D., of the Memorial Sloan Kettering Cancer Center, will use their new imaging system to study the growth characteristics of GFP-expressing tumors in the lung, liver and brain. This collaborative effort brings together researchers with expertise in optical tomographic instrumentation and algorithm development, and expertise in GFP reporter gene design and cancer research involving small animal imaging.

“Our interdisciplinary research team believes that limitations related to existing instrumentation for optical tomography can be overcome by an imaging system that uses a frequency-domain light propagation model based on the equation of radiative transfer,” said Dr. Hielscher. “We expect that, in combination with instrumentation that allows for modulation frequencies higher than the currently available 150MHz, there will be better spatial resolution so that we can see and monitor the growth characteristics of various tumor cells in vivo.”

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