Image by Satre Stuelke

A CT scan of a McDonald's Big Mac sandwich.

Check out Stuelke’s Web site for more radiology art.

Despite having a less convoluted birth canal, Neandertals felt the difficult pangs of childbirth just like modern humans do, according to a recent study of a female Neandertal pelvis unearthed in Israel more than 70 years ago.

Unlike our ape and monkey relatives, human babies are about the same size as the birth canal, making for a “difficult” passage, the two male authors write. (How’s that for an understatement?)

In fact, the human birth canal is twisted, wider than it is long in some places, and longer than it is wide in others. This means that babies must twist as they make their egress: entering the birth canal sideways, the baby must rotate so its head is down, and then rotate again to allow its shoulders to pass.

When did the ape’s birth canal evolve into the twisted, and painful, human version? Timothy Weaver and Jean-Jacques Hublin used CT scans to reconstruct a birth canal from pelvic bone fossil fragments from a Neandertal and compared this to data from pelvic bones from modern humans.

Weaver and Hublin’s reconstruction suggest that the Neandertal’s birth canal was less twisted than that of modern humans. But the pelvic area in Neandertals and modern humans is similar, suggesting that even though Neandertal babies didn’t have to twist as much during delivery, their size relative to the birth canal was close enough to insure a painful passage.

The results mean that changes in childbirth probably occurred “quite late in human evolution, during the last few hundred thousand years.”

A word of caution - this type of research relies on intact fossils. The pelvis survives very poorly, which is why scientists must rely on sophisticated reconstruction techniques. The current study is based on bone from a single Neandertal, making it difficult to take normal variations present within a species into account.

You know the cliché that science knows no borders? The current study was written by a scientist in the United States and one in Germany - examining a specimen discovered in Israel by a British archaeologist - using imaging technology developed by scientists from South Africa and the United Kingdom (one of whom worked in the United States).

Source: “Neandertal birth canal shape and the evolution of human childbirth” by Timothy D. Weaver and Jean-Jacques Hublin published April 20 online in PNAS (doi: 10.1073/pnas.0812554106).

A 40,000 year-old baby mammoth

Last month I spoke with Satre Stuelke, the artist turned medical student who is using CT scans to produce works of art. Reuters recently did a great little video about his work, highlighting how he is using the CT scanner as a camera. CT scanners use X-rays instead of light to capture images.

Unconventional uses of CT scans are in the news this month - the current issue of National Geographic features a cover story on a well-preserved 40,000 year-old frozen mammoth. Scientists used CT scans to learn more about the mammoth’s anatomy and the cause of her death. The scan revealed sediment blocking nasal passages in her trunk, suggesting that she died from asphyxiation after drowning in mud.

In February I wrote about using CT scans to analyze fossils. Now I have uncovered another unusual application of the technology: Art.

Satre Stuelke, a third-year medical student at Weill Cornell Medical College in New York, is putting everyday objects into a scanner and producing works of art.

He told me that during his first year in medical school, he thought about using a CT scanner to “analyze culturally significant objects, looking for some sort of pathology,” much like we scan humans looking for something out of the ordinary.

His Web site now includes dozens of images, including an iPod, a McDonald’s BigMac sandwich, and a Barbie doll (check her out on the left).

A CT scan reveals that Barbie has a “rather detailed skeletal structure, most extensively present in the legs.” Much of Stuelke’s descriptions use the passive voice and anatomical terms of medical imaging. An iPod: “Behind the screen and to the most cephalic extreme of the body, a gray battery pack can be seen …. Note the headphone jack in the upper right part of the image proximal to the battery pack.”

Stuelke attended medical school at the University of Iowa from 1988 to 1990, but dropped out to become an artist. After attending graduate school at the Art Institute of Chicago, he established himself in the art world with a faculty position in New York and more than 60 art shows.

A confluence of events – the September 11, 2001, attacks (which occurred 1,600 meters from his work), a search for obstetricians in preparation for having a baby, and the increasing lack of challenge in the art world – led Stuelke to return to medical school.

Stuelke is now in the unusual position of being a third-year medical student in his fifth year of medical school. He received no credit for the time he spent in Iowa, which might be just as well. He says that he remembers some of his previous medical training, but a lot has changed in 20 years, particularly genetics, immunology, developmental biology and endocrinology.

The university allows him to use an older CT scanner that is only used for research, and only when scientists are not using it. Stuelke remembers asking whether he could put a frozen dinner in the scanner, for artistic purposes. The medical director eventually answered, “we could support the arts.” You can see that result below.

The New York Times covered Stuelke’s work on March 23, and today his pager was beeping with media requests. His attending physician, Dr. Erica Jones, generously gave him the day off, which explains why he had time to speak with me.

After he receives his medical degree, Stuelke plans to specialize in – what else? – radiology.

Ted Pietsch and colleagues from the University of Washington discovered a new species of fish with a psychedelic pigment pattern.

In June 1992, staff from the Dallas Aquarium found two frogfish with an unusual pigment pattern amid a shipment of live fish from Bali. The “paisley anglers” arrived in poor condition and didn’t last long. They were preserved in ethanol and shipped to Pietsch for study.

Unbeknownst to the scientists, the fish’s color fades in ethanol. So Pietsch, making only a superficial examination, placed the seemingly unremarkable white fish on a shelf and ignored them for 16 years.

In January 2008, Toby Fadirsyair, a guide, and Buck and Fitrie Randolph, two of the co-owners of Maluku Divers in Ambon Island, Indonesia, spotted a psychedelic fish. The local diving community had never seen anything like it, so photos were sent to Pietsch, who wrote “I can say that in my 40 years studying frogfishes, and anglerfishes in general, I have never seen one quite like this.”

Detailed study, including DNA analysis, supports Pietsch’s original conclusion – these fish are a new species of Histiophryne, frogfish whose leg-like fins allow them to hop along the sea floor.

Another unique feature of the psychedelic fish – its eyes face forward, suggesting that, like humans, it may have binocular vision. Most fish have eyes on each side of the head, so each eye’s field of vision does not overlap.

Re-examining the 16-year-old “paisley angler” specimens, Pietsch found that though their skin appeared white, the distinctive striping pattern was visible under the microscope.

Pietsch will have the honor of giving the new species a scientific name. The current favorite? Histiophryne psychedelica.

Source: “A Bizarre New Species of Frogfish of the Genus Histiophryne (Lophiiformes: Antennariidae) from Ambon and Bali, Indonesia” by Theodore W Pietsch, Rachel J. Arnold and David J. Hall, published in the February issue of Copeia.

Today we celebrate the birthday of Allan M. Cormack, inventor of the CAT scan, who would have turned 85 today (he died in 1998).

A CAT scan (computer assisted tomography or computed axial tomography or computed tomography, CT) is a three-dimensional (3D) image reconstructed from a series of two-dimensional X-ray images. Compared with a conventional X-ray image, a CAT scan provides better resolution, which helps identify the position, size and shape of tumors, among other medical applications.

Cormack won the Nobel Prize in medicine in 1979 for discovering the mathematical formulas that allow scientists to reconstruct an object’s cross section from a series of two-dimensional X-ray images. (Co-winner Godfrey Hounsfield constructed the first CAT scan system used in medical care.)

Other imaging methods, such as magnetic resonance imaging (MRI, Nobel Prize 2003), frequently are used in medicine today, but computed tomography is still popular among scientists. Structural biologists use cryo-electron tomography to reconstruct 3D images of proteins from multiple 2D images taken using an electron microscope. This technique is similar to a CAT scan, except the specimen is frozen and repeatedly tilted to acquire images from different angles (in a medical CAT scan, the patient lies still, at room temperature, while the X-ray source rotates around the patient).

Researchers also use a variation of the CAT scan to examine fossils. High-resolution X-ray CT can resolve much finer details than medical CAT scans, probably because radiation exposure is not an issue with animal remains.

My favorite use of CT scanning? Rather than disassembling a vintage guitar to see how it was built, scientists used CT scans to determine how the instrument’s bracing was assembled (see photo). The Gretsch model 6120 was manufactured with unique bracing from 1959-1961. Once the CT scan revealed the instrument’s exact measurements, guitar makers were able to recreate the unique bracing.

Know of other unusual applications for CT scanning?

Our eyes, like cameras and microscopes, focus light using lenses – that’s refraction. For example, look at an object through water, like a straw in a filled glass, and the object will appear distorted.

Many telescopes, on the other hand, focus light using mirrors – that’s reflection.

Crustaceans such as scallops, lobsters and prawns have mirrors in their eyes, but this phenomenon had never been observed in vertebrates, until last month, when a team of scientists from Germany, the United Kingdom and the United States discovered the Brownsnout spookfish uses reflection to see.

Mirrors are common in animal eyes, but they usually aren’t used to focus light, like a lens. The eye-shine of cats is due to a reflective membrane, the tapetum lucidum, that sits behind the retina. Incoming light (refracted through the lens) that doesn’t get captured by photoreceptors in the retina is reflected back into the photoreceptors by the tapeta. “Light-doubling” systems like this are prevalent in nocturnal animals like sharks, crocodiles, and spiders.

In this picture of the spookfish, looking down at the head (in science jargon this is a dorsal view, anterior to the top), you can see that each eye has two parts that receive light. One part faces up, toward the ocean’s surface as the fish swims, and focuses light using refraction. These main parts appear colored in the photo. The second part of each eye faces downward (black in the photo), and contains stacks of crystals that reflect light onto the retina, enabling the spookfish to produce brighter images of the deep.

The spookfish Dolichopteryx longipes has been described only once before, in a 1973 paper. It was a dead, preserved specimen so authors had to make assumptions – some that turned out to be erroneous – about its anatomy. Kudos to Hans-Joachim Wagner and colleagues for collecting a live spookfish from a depth somewhere between 600 and 800 meters in the South Pacific.

Perhaps the most impressive aspect of the study is a technical one: having only a single specimen left the authors little margin for error in their examination. I’ve spent months slicing zebrafish tissue into thin sections and examining them under the microscope. Even on the best days no sample was perfect, but I had dozens of samples available. Wagner and colleagues only had one. If they had botched their preparation, we might never have learned that at least one vertebrate animal uses reflection to form images.

Source: “A Novel Vertebrate Eye Using Both Refractive and Reflective Optics” by Hans-Joachim Wagner, Ron H. Douglas, Tamara M. Frank, Nicholas W. Roberts, and Julian C. Partridge, published in Current Biology, January 27, 2009.