BERLIN - Researchers in Germany have used a modern medical procedure to uncover a secret within one of ancient Egypt's most treasured artworks -- the bust of Nefertiti has two faces.

A team led by Dr. Alexander Huppertz, director of the Imaging Science Institute at Berlin's Charite hospital and medical school, discovered a detailed stone carving that differs from the external stucco face when they performed a computed tomography, or CT, scan on the bust.

The findings, published Tuesday in the monthly journal Radiology, are the first to show that the stone core of the statue is a highly detailed sculpture of the queen, Huppertz said.

"Until we did this scan, how deep the stucco was and whether a second face was underneath it was unknown," he said. "The hypothesis was that the stone underneath was just a support."

The differences between the faces, though slight -- creases at the corners of the mouth, a bump on the nose of the stone version -- suggest to Huppertz that someone expressly ordered the adjustments between stone and stucco when royal sculptors immortalized the wife of Pharaoh Akhenaten 3,300 years ago.

"Changes were made, but some of them are positive, others are negative," Huppertz said.

John H. Taylor, a curator for Ancient Egypt and Sudan at the British Museum in London, said the scan raises interesting questions about why the features were adjusted -- but that answers will probably remain elusive.

"One could deduce that the final version was considered in some way more acceptable than the 'hidden' one, though caution is needed in attempting to explain the significance of these changes," Taylor wrote in an e-mail.

The bust underwent a similar CT scan in 1992. But the more primitive scanner used then only generated cross sections of the statue every 5 millimeters -- not enough detail, Huppertz said, to reveal the subtlety of the carving hidden just 1-2 millimeters under the stucco.

Egyptologist Ludwig Borchardt discovered the bust in 1912 and added it to Berlin's Egyptian collection on Museum Island, a cluster of five neoclassical art halls that make up one of the city's most familiar landmarks.

Currently on display at the Altes Museum, the bust will move next door when the Neues Museum reopens in October after a lengthy restoration by British architect David Chipperfield.

In 2007, Wildung denied a request from Egypt's antiquities chief to borrow the bust for an exhibition, saying it was too fragile to transport. Huppertz said the results of his scan added credence to that claim.

Taylor, the British Museum curator, said the better understanding of the bust's structure will also help preserve it.

"The findings are particularly significant for the information they shed on the constructional process and the subsurface condition of the bust, which will be of value in ensuring its long-term survival in good condition" Taylor said.