PARIS - Is the Mona Lisa headed for surgery?
Leonardo da Vinci's 500-year-old painting of the woman with the mysterious smile will go under the microscope and be X-rayed for the first time in a half-century to determine what's causing it to warp.
The world's most famous portrait, painted in Italy over several years beginning about 1505, has long been known to be fragile. The oil sits on a half-inch poplar board that has undergone many nips and tucks over time.
Last week, the Louvre Museum said warping was discovered during a recent routine check and announced a new study of the painting. The examinations will be done when the museum is closed - allowing Leonardo's masterpiece to remain on public display.
Vincent Pomarede, chief curator in the Louvre's department of painting, said the study will help determine whether past repairs did more harm than good - and whether new work is needed.
"We're launching this study to understand exactly what's happening," he told Associated Press Television News.
"On the other hand, we think perhaps at a certain time we might have to intervene, not at all on the picture layer, but the back, on the panel itself," Pomarede said.
"We are going to use the chance to examine it in ways that we've not been able to in previous years," he added, saying that high-tech microscopes would be used as well as X-rays, last taken in the 1950s.
Previous work on the portrait has included attaching a brace made of strips of wood to the back of the painting to prevent a crack in the poplar panel from worsening.
The cause of the crack is not known, Pomarede said.
For curators, the worry is that the warping could one day worsen the crack or cause the painted image to bulge. "Obviously that would be a big problem," he said.
"Today, all this isn't evolving the way we'd like it to," Pomarede said. "The convex form is warping in different ways - there is one side moving more, and faster, than the other."
Nearly all 6 million visitors to the Louvre each year see the Mona Lisa. It reportedly has enjoyed an increase in American visitors due to Dan Brown's best-selling novel, "The Da Vinci Code."
For the Mona Lisa, little is left to chance: It's housed in an air-conditioned, bulletproof glass case and the humidity inside is carefully controlled.
Pomarede doesn't believe the daily barrage of camera flashes by tourists are damaging the painting, because the glass filters out all ultraviolet and most infrared light.
"It is more likely that (the warping is due) to pieces of wood added in the 17th and 18th centuries, and again in the middle of the 20th century," Pomarede said. He suspects a "different aging pattern" of the various pieces of wood is causing the Mona Lisa to warp.
The masterpiece has been through hard times. During World War II, French authorities hid the painting in small towns to keep it out of the hands of German forces. In 1911, an Italian house painter stole the Mona Lisa; it was recovered two years later in Florence and returned to France.
Pomarede says he's not too worried about the painting in the long run.
"Leonardo da Vinci worked brilliantly, and he knew perfectly well the evolution of materials," Pomarede said. "She's 500 years old and if we preserve her properly she will still be there 500 from now."