August 24, 2009 - By Stephanie Pappas
Detailed scans at Stanford help reveal the secrets of an ancient Egyptian priest
Elizabeth Cornu (left) and Alisa Eagleston (right), conservators at the Fine Arts Museums of San Francisco, load the mummy of Iret-net Hor-irw onto a cart in a conservation lab in the de Young Museum on Aug. 20.
To the naked eye, the linen-swathed remains of Iret-net Hor-irw reveal little. A blackened fingernail and the leathery soles of two ancient feet are the only visible hints of the mummified Egyptian priest inside his wrappings. But on Aug. 20, with the help of a high-resolution CT scanner at Stanford, the ancient mummy came into sharp focus: a smooth, unbroken skull with a full set of teeth, two arms carefully crossed over the chest and an assortment of dark shapes that seemed to orbit his bones.
“You’ve got a pillow amulet at the base of the skull,” said Egyptologist Jonathan Elias, PhD, peering at a computer monitor in the School of Medicine’s AxiomLab, where physicist Rebecca Fahrig, PhD, was overseeing the computed tomography imaging of the 2,500-year-old mummy. Elias, who is part of the Pennsylvania-based Akhmim Mummy Studies Consortium, pointed to a dark rectangle at the intersection of the skull and vertebrae. “It’s exactly where it should be,” he said.
The amulet, a powerful symbol of protection for the ancient Egyptians, is the first of what researchers hope will be a long line of discoveries about Iret-net Hor-irw, who has belonged to the Fine Arts Museums of San Francisco since 1917. Researchers will use images from the scans to create three-dimensional computer models of the mummy’s skeleton. In the process, they’ll examine his bones and wrappings for hints about his age, height, health and death. The CT scans also revealed the shape of the mummy’s skull, which will allow researchers to reconstruct and sculpt his face.
“This is a really comprehensive CT investigation of this mummy,” said Fahrig, an associate professor of radiology at the medical school. “Everything we can throw at it, we’re going to.”
Researchers hope the scans will add to their limited knowledge of Iret-net Hor-irw. Writings on the man’s coffin suggest that he was a minor priest to the gods Osiris and Min in the east Nile city of Akhmim. He died around 500 B.C., probably in his 20s. In the late 1800s, someone excavated him from Akhmim’s large cemetery and sold his body, likely to a tourist. By 1917, he was in California, where a private owner donated him to the Fine Arts Museums. He has been on loan to the Haggin Museum in Stockton since 1944, where he remained on display until Aug. 18, when conservators carefully packed and transported him to San Francisco in preparation for an upcoming show at the Legion of Honor Museum. The exhibition, “Very Postmortem: Mummies and Medicine,” opens Oct. 31.
“I wanted to show the mummy now as a resource, a way of understanding how people lived and how they died,” said Renee Dreyfus, PhD, curator of ancient art for the Fine Arts Museums. “Our working together with Stanford is our golden opportunity.”
This is the second mummy scan for Fahrig, who helped to image the mummy of an Egyptian child belonging to the Rosicrucian Museum in San Jose in 2005. Fahrig’s lab contains a CT scanner with a rotating arm, which enables researchers to capture images from multiple angles without moving the patient. The images available from the machine are up to six times sharper than images from a typical hospital CT scanner.
The mummy’s dried-out state does create challenges, Fahrig said. The CT machine picks up on boundaries between different density tissues. In a live patient, those boundaries are usually “bone/water,” Fahrig said: dry bone bordering wet tissue. In a desiccated mummy, the boundaries are bone/air. These sharp boundaries can confuse the CT, leading to artifacts, or shadowy figures that aren’t really there. On the other hand, Fehrig said, a mummy’s postmortem stillness does have some advantages for getting a sharp image.
“When you tell them not to breathe, they don’t breathe,” she said.
The scans almost immediately revealed some of the mummy’s secrets: His internal organs are mummified in linen pouches placed back inside his torso, as was common at the time. He was laid to rest with a scarab beetle amulet on his forehead, representing eternal being. Above his right eye is a two-plumes amulet, a symbol of fertility and the good life. The pillow amulet at the back of his head represents an Egyptian headrest, a magical object of protection. Finally, the mummy clutches one more amulet in his hand: a sacred eye of Horus, another powerful, protective talisman.
“This seems to be a well-thought-out amulet placement and one that was quite normal at the time,” Elias said. Finding amulets was exciting, he said, because not all mummies have them. Finding them in the correct positions was even better, he added, as it suggests that the mummy’s embalmers were diligent.
Once the images are fully processed in the next several weeks, researchers may find more amulets on Iret-net Hor-irw. Thanks to a second set of scans, done at a separate Stanford location—the medical center's Imaging Center on Sherman Avenue in Palo Alto—researchers may also be able to determine what the amulets were made of. These additional scans were done with a dual-energy CT scanner, which uses two frequencies of X-rays to better differentiate between different materials. The data from those scans should help Egyptologists understand the materials used in the mummification process.
Meanwhile, anatomists will sculpt flesh onto a model of the man’s skull, revealing his face for the first time in thousands of years. They’re hoping to find a family resemblance to a mummy currently in Tacoma, Wash., who is believed to be a relative of Iret-net. Researchers will examine the scans for any insights into the man’s health and death, and may also use the ultra-crisp images as a teaching tool for anatomy classes, said Paul Brown, DDS, a researcher at the Stanford-NASA Biocomputation Center who has been involved with both Stanford mummy scans.
The day’s images were everything researchers had hoped for, Fahrig said. In fact, the pictures were so sharp that researchers can make out the grooves in the ancient man’s teeth.
It was exciting to get such clear images, Fahrig said. But when she peers beneath the priest’s tattered wrappings, she sees more than just a collection of baubles and bones.
“I see something that tells me so much about that person and that time,” she said. “What I see is a piece of history.
Stephanie Pappas is a science-writing intern in the Office of Communication & Public Affairs.
Stanford Medicine integrates research, medical education and health care at its three institutions - Stanford University School of Medicine, Stanford Health Care (formerly Stanford Hospital & Clinics), and Lucile Packard Children's Hospital Stanford. For more information, please visit the Office of Communication & Public Affairs site at http://mednews.stanford.edu.