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Prof. David D. Nolte

October 17, 2002

Holographic Video "Fly-Throughs" of Cancer Tissue

Prof. David D. Nolte

Dept. of Physics
Purdue University

A long-standing effort of biomedical imaging has been the search for clinical situations where optical (non-ionizing) imaging can replace x-ray imaging without sacrificing (and indeed contributing) valuable diagnostic information. The search has been significantly aided by the fact that light is not strongly absorbed as it propagates through most biological tissue in the near infrared, even though it is significantly scattered.

We use self-adaptive optics to construct a "vibration-free" interferometer that requires neither vibration isolation nor active damping to selectively peer inside living tissue. The interferometer is constructed from a dynamic holographic film that acts as a coherence filter. It is inserted directly before a video camera and passes full-frame coherent image-bearing light from a given depth, while rejecting scattered background. Because of its use as a simple filter in the optical imaging path, it provides direct images in principle without computed reconstructions, much like putting on a pair of polarized sun-glass to remove the bright "glare" that obscures the weak coherent images. It is depth-gated, making it possible to fly through scattering tissue as a succession of optical sections.

Here we demonstrate the first in vitro fly-through images of living tissue. The fly-through data consist of cross-sectional video frames recorded by a digital camera from successive depths inside rat osteogenic sarcoma tumor spheroids in vitro. An optoelectronic semiconductor device is used as an adaptive (self-updating) holographic film that acts as a simple coherence filter. It passes image-bearing light to the camera during holographic read-out, while rejecting the usually obscurring scattered light coming from tissue at other depths. The data from the tumor spheroids reveal heterogeneous structure presumably caused by necrosis and microcalcifications characteristic of human tumors.