How They Did It

By David Bjerklie

With just a few keystrokes, Alexander Tsiaras does the impossible. He takes the image of a 56-day-old human embryo and peers through its skin, revealing liver, lungs, a bulblike brain and the tiny, exquisite vertebrae of a developing spine.

These are no ordinary baby pictures. What Tsiaras and his colleagues are manipulating are layers of data gathered by CT scans, micro magnetic resonance imaging (MRI) and other visualization techniques. When Lennart Nilsson took his groundbreaking photographs in the 1960s, he was limited to what he could innovatively capture with a flash camera. Since then, says Tsiaras, "there's been a revolution in imaging."

What's changed is that development can now be viewed through a wide variety of prisms, using different forms of energy to illuminate different aspects of the fetus. CT scans, for example, are especially good at showing bone, and MRI is excellent for soft tissue. These two-dimensional layers of information are assembled, using sophisticated computer software, into a three-dimensional whole.

The results are painstakingly accurate and aesthetically stunning. Tsiaras, who trained as a painter and sculptor, used medical specimens from the Carnegie Human Embryology Collection at the National Museum of Health and Medicine in Washington as models for all but a few images. The specimens came from a variety of sources, according to museum director Adrianne Noe, including miscarriages and medically necessary procedures. None were acquired from elective abortions. --By David Bjerklie