Anand Kumar, Ph.D.
Assistant Professor
Department of Radiology
Massachusetts General Hospital

“Molecular imaging with time domain fluorescence”

Molecular imaging combines the use of disease targeted contrast agents with advanced imaging techniques to visualize intact living organisms from the small animal to the human scale. Established techniques for whole animal imaging, including positron emission tomography (PET) and magnetic resonance imaging (MRI) offer high resolution and depth penetration but have limited flexibility in spectral and lifetime multiplexing. They are also expensive, highly complex in design, require significant expertise for their operation and maintenance. Optical techniques are emerging as a cost effective and portable alternative for functional contrast, and are particularly attractive given the potential for a rich variety of fluorescent contrast agents with spectral and fluorescence lifetime tunability.

Our laboratory is focused on whole body time domain techniques, with emphasis on lifetime contrast. Although fluorescence lifetime imaging is well established for microscopy (FLIM), whole body lifetime imaging is relatively recent. This can be attributed in part to the mathematical complexity involved in modeling time-resolved fluorescence in tissue. The imaging of fluorescent lifetimes through turbid media requires the separate consideration of two phenomena. The first is the interaction of the fluorophore with the biological environment (e.g., pH, protein binding, activation) which can shift the natural lifetime of the fluorophore. This shift can be well characterized in advance using careful control measurements. The second phenomenon, the main focus of our research, is the interaction of light with tissue, which can also indirectly affect the apparent lifetime of the fluorophore as measured on the surface of the subject.

This presentation will outline theoretical and experimental methods centered on a “tomographic FLIM” model. This model is valid under a widely applicable condition, namely that the fluorescence lifetime is longer than the intrinsic diffusive timescales in the medium, and naturally leads to an elegant algorithm for tomographic FLIM that allows the separate 3-D localization of multiple lifetimes present within biological tissue. The presentation will also include recent extensions of this work to the spatial frequency domain, and in vivo applications pertaining to cancer and cardiac disease models.

Anand Kumar is Assistant Professor at the Massachusetts General Hospital in Boston. Dr. Kumar received his M.Sc. and Ph. D. degrees from the Indian Institute of Technology, Chennai, India and Northeastern University, Boston, respectively, all in Physics. His research focus is on diffuse optical tomography and optical molecular imaging.

Wednesday February 6, 2013
4:15 PM
GBSF Room 4202