Putting a finger on a person's age

There are many ways to estimate a person's age -- gray hair, wrinkles, acne. Israeli inventor Shmuel Levin thinks he's found a better way, by measuring a person's middle finger. It may sound odd, but Levin's idea has caught the attention of RSA Security Inc. of Bedford, a leading maker of computer security products. RSA and Levin's company, I-Secure of Tel Aviv, are teaming up in hopes of creating products that will protect children from inappropriate Internet content, or prevent adult child molesters from entering Internet chat rooms meant for kids.

"We are very happy with the support and the partnership we have with RSA," said Levin, an electrical engineer who has previously worked on artificial limbs that can be controlled by electrical impulses from the user's muscles.

In search of a new market, Levin and his colleagues decided on biometrics -- the science of identifying someone by precise measurement of physical features.

Their research on human anatomy led them to the idea of measuring age by studying the size and structure of bones. Levin found that the structure of a bone in the middle finger called the proximal phalanx is a reliable indicator of a person's age. The finger bone features a "growth plate" of cartilage.

"When you're young, it consists more of cartilage," said Levin. But as the years go by, the growth plate "ossifies," or turns to solid bone. Levin and his colleagues say they can use the size and condition of the growth plate to estimate age.

To view the bone, the I-Mature system uses a small device that emits low-frequency ultrasound, using the echoes through the finger to draw a digital picture of the digit. This data is fed to a computer that estimates the person's age. "It is not invasive and absolutely safe," said Levin.

The concept fascinated Burt Kaliski, chief scientist at RSA Labs. "We were intrigued by the very existence of this technology," he said. RSA saw an opportunity to build the I-Mature system into computer security products for use in schools and public libraries, to prevent kids from going to the Internet's rougher neighborhoods.

But the I-Mature system has its limits. Humans don't all grow at the same rate, so the system can't deliver exact age measurements. It can tell that one person is an adult, and another is a child. But it can't distinguish between a 17-year-old and an 18-year-old.

"They do this by age group . . . rather than predicting the actual age of the individual," said Kaliski. "They're saying, 'Does this person appear to be under 14 or over 14?' "

That's not good enough, in the view of Herb Lin, senior scientist at the National Research Council, which is associated with the National Academy of Sciences. Lin co-edited a 2002 report on shielding children from Internet pornography. He said that companies like AOL, which offer chaperoned Internet services for children, will work just as well as the I-Mature system.

"I'm not sure what problem they're trying to solve," Lin said.

Lin also cast doubt on the accuracy of the I-Mature system. He cited his own daughter, who suffers from a growth hormone deficiency and receives regular bone scans.

"She's 10 now," said Lin. "Her bone age is about 8." Any unusually small or large child would deceive the scanner, he said.

Still, Levin thinks his device is accurate enough to distinguish between children and adults, and he believes that's good enough to generate demand for the product. He hopes that with RSA's help, he can get the I-Mature adopted in schools and libraries. After that, Levin hopes to offer a version that would connect to a home PC and sell for around $25.

Hiawatha Bray can be reached at bray@globe.com.