Digital volumetric holograms for medical imaging

An interview with Allan Wolfe and Stephen Hart, Voxel

Adapted from OE Reports, No. 159, p. 5-7, March 1997. Scanned, filtered by optical character recognition. For further details please see the original article.

How did this technology, volumetric holograms, start for you folks? And how did it find its way into medical imaging?

Stephen Hart: I was at Imperial College, London, in the applied optics and astrophysics groups there. Our group had built an imaging, scanning Fabry-Perot interferometer for astronomical use, which could, in a very short period of time on a telescope, get, instead of a 2D image, a 3D volume of data. We had x and y on the sky and our z dimension was wavelength. We could map out the red and blue shifts of receding and approaching gases, respectively, in different astrophysical objects. I had all this 3D data on which I had done all the computer graphics things, but I still didn't understand this information.

Allan Wolfe: When I first met Stephen, they bad the technology that enabled them to produce real volumes. We started thinking about the various potential applications and, for a variety of reasons, medical imaging (Figure 1) made sense to us. Over the last couple of decades, physicians realized that viewing and knowing everything that was in -a volume was important, and the development of technologies like computer tomography (CT) and magnetic resonance (MR) made it possible to collect information about the volume. What remained was to look at the volume in some coherent way, because existing displays only showed the volume as a series of 2D pictures rather than a real 3D image.

Hart: In the astronomical objects I was looking at, we weren't quite sure what it was we should be seeing. Holography gave me a way to directly print those slices, one behind the other, in three dimensions, and actually see the structure of the objects. But, as an astronomer, we get a few data sets like that a year, whereas in radiology, something like 50 million times a year world wide, a patient undergoes a CT or MR scan. As far as this technology is concerned, that sort of data is identical to astronomical data. It's parallel slices, all 2D, black and white images, and somebody, in this case, a radiologist or surgeon, is trying to understand what the structures are, how things interrelate, e.g., how blood vessels relate to tumor tissue.

When did you folks found this company?

Wolfe: It was 1988. Initially, we were trying to confirm if we had a viable product.

Figure 1. In the process of operating on a large brain tumor in the region of the acoustic canal in a patient with neurofibromatosis, Dr. John Cornns (Tripler Army Medical Center, Honolulu), inserted a cotton swab in the cavity where he was excavating the tumor. By directly comparing the volume of the cotton swab to the tumor in the life-size hologram of the patient, he was able to determine that he had removed only 1/3 of the tumor.