Researchers at Purdue University and the Imperial College of Science
in London have created a real-time holographic system to acquire a fly-through
movie of living tissue using infrared light and a special, semiconductor
holographic film. The acquired images showed structure inside rat tumors
that, with conventional techniques, would only be visible if the tumor
was sectioned into thin slices or imaged with ionizing radiation.
The researchers created the fly-through movie using optical coherence
imaging (OCI). OCI is related to the more widely known optical coherence
tomography (OCT). However, OCT involves scanning a laser beam through
a sample and gathering information point by point, which then must be
assembled into a complete image. OCI, on the other hand, captures complete
images of thin tissue sections that can be recorded directly with a
The key to the holographic OCI technique is a dynamic holographic film
that filters out the scattered, incoherent background light but passes
the coherent, full-frame images to a camera. Tissue readily reflects
image-bearing infrared light, but it also strongly scatters the light,
and without coherence filtering the scattered light would overwhelm
the coherent pictures.
By adjusting the relative delay between the image beam and the reference
beam in the OCI system's imaging interferometer, the researchers (Ping
Yu, 765-494-3004, email@example.com, David Nolte, 765-494-3013,
firstname.lastname@example.org) could control the depth of the images and
assemble a slice-by-slice tour through a tumor while leaving the tissue
Application of the OCI technique to cultured rat tumors revealed structures
that appeared to be necroses (regions of dead tissue) and calcifications
much like those found in human cancers (see image).
Ultimately, the researchers explain, holographic OCI could offer a
nondestructive alternative to x-rays and microsectioning methods for
studying living tissue. (P.
Yu et al., Applied Physics Letters, 21 July 2003.)