In August 1985, Mizuo Shinohara, D.D.S., Ph.D., a dentist and forensic scientist, was one of more than 2,800 doctors, dentists and scientists called to the scene of the horrific Japan Airlines Flight 123 crash on Mount Takamagahara in Japan’s Gunma Prefecture. Selecting from 215,150 possible pairs of dental radiographs, Dr. Shinohara and others worked for more than three months to identify the burned remains of 520 people. The pain of victims’ families was compounded by a Japanese Buddhist tradition calling for the burial or cremation of human remains within a week to 10 days.

Dr. Shinohara’s daughter, Eiko Kosuge, D.D.S., Ph.D., remembers her father’s efforts at the crash site. “His stories from that time, plus stories of grieving families anxiously waiting for loved ones, inspired me to automate the process,” said Dr. Kosuge, who presented her system at RSNA 2007.

“Manual dental identification works fine when the number of victims is low—for example, a house fire or single auto accident,” said Dr. Kosuge, of the Shinohara Dental Clinic and the Department of Oral and Maxillofacial Radiology at the Kanagawa Dental College. “However, as the number of victims increases, the time required to identify the bodies increases exponentially and the risk of identification error increases sharply as well.”

To automate the process, Dr. Kosuge had to overcome technical obstacles such as the lack of consistency of angle when dental X-rays are taken. Separate radiographs of the same tooth have distortions of rotation, translation and scale, altering the tooth’s appearance.

A breakthrough came with the help of Koichi Ito, Ph.D., an assistant professor in the Graduate School of Information Sciences at Tohoku University. Dr. Ito realized that the phase-only correlation (POC) algorithm used to identify fingerprints and align satellite images could be employed to eliminate distortions when comparing dental records.

The POC matching system evaluates two images, assigns them a matching score and creates a candidate list of possible matches for each X-ray. By eliminating about 95 percent of all possible matches and offering a list of the three top candidates, Dr. Kosuge said the system “will cut the time required to produce matches to about 3.6 seconds per pair and dramatically cut the workload of forensic scientists.”

For example, in the case of the 1985 Japan Airlines crash, her father and his co-workers would have only had to evaluate around 10,000 possible matches instead of more than 200,000.

Recently testing the POC matching system using dental records from 60 people, Dr. Kosuge and her team achieved 100 percent matching.

The team was also excited to discover that they were still able to produce matches even in cases of small changes in tooth structures. “This is important because victims will often experience some sort of dental work or damage after their last X-ray,” said Dr. Kosuge.

Dr. Kosuge said that for her, it all comes back to alleviating the suffering of the victims’ families. “Perhaps the most important advancement is cultural in nature,” she said. “If our system had been used in the Japan Airlines crash, the remains of loved ones could have returned to families in days instead of months.”

This article was adapted from a story that appeared in the RSNA 2007 Daily Bulletin. The daily newspapers from the annual meeting are available online at RSNA.org/bulletin.