Dutch medical physicist Arie van 't Riet spent his career working in the departments of radiotherapy, radiology, and nuclear medicine in various hospitals. One day, while training radiographers and physicians, he hit on a novel way of demonstrating the effect of the thickness of a material on X-ray absorption. "I chose flowers," he says. "The thickness of the leaf differs from the thickness of the stem of the flower, but it’s all the same material."
Van 't Riet began making X-rays of plants and flowers back in 2007, and subsequently began to digitize, invert, and partially color them. "Some people told me ‘That's art,’" he says. "And I became an artist." He describes the process in his TedX talk from last month:
He moved on to capturing animals in his images, starting with stuffed specimens from a taxidermist, which weren’t a great success as he explains in his talk, and progressing to using roadkill and the unfortunate victims of his cat. The radiation used in taking the X-rays would damage live animals, so he only uses the bodies of the deceased. Now Van 't Riet creates entire staged natural scenes that he calls "bioramas." "X-rays of flowers you will find all over Internet," he says. "X-rays of complete natural scenes as I make them I think are unique."
An X-ray machine is a type of camera which uses electromagnetic waves called X-rays instead of visible light to expose the film. Bone, fat, muscle, and tumors absorb X-rays to different degrees because of the variation in the density of the tissues. With normal light, you see the surface of an object in color. With X-rays, you see the internal structure in grayscale.
Van 't Riet has his own studio with X-ray equipment and a license to use it. To create a biorama, the artist takes flowers, animals, and other natural objects and arranges them in a simulated natural scene. He calculates the energy and amount of X-ray radiation required to get a well-exposed X-ray film of that specific biorama.
"Technically, these X-rays of bioramas are much more challenging than just flowers," Van 't Riet explains. "That’s because of the large difference in X-ray absorption between the thin leaves and the thick animal." Thin leaves require very low-energy X-rays, while you need high-energy rays for animals. For that reason, Van 't Riet sometimes needs to block off certain parts of the scene and take multiple X-rays.
The film is placed on one side of the biorama, the X-ray tube on the other. Turn the beam on and the X-ray film is exposed. The X-ray film is developed and digitized. The digital image is then inverted and finally partly colored.
Van 't Riet would like to add more reptiles, exotic fishes, and birds with pronounced beaks to his work. Van 't Riet has also made 3-D visualizations of his bioramas. The X-ray tube is rotated around the biorama making a new X-ray every 10 degrees. The multiple still images of the scene are combined into a video animation.
Now retired from the hospital, Van 't Riet continues to work in his studio. "Looking with X-ray eyes added a new dimension to my experience of nature," he says. "My eyes only can see the outer surface. My X-rays look inside. And that inner always fascinates me."