Polish scientists say they've used a medical imaging technique to detect the forgery of an artist's signature and changes in paintings hundreds of years old.

Associate Professor Piotr Targowski of Nicolaus Copernicus University in Torun, Poland, said easel paintings prepared according to traditional techniques consist of multiple layers. The artist, for instance, first applies a glue sizing over the canvas to ensure proper adhesion of later layers. Those layers may include an outline of the painting, the painting itself, layers of semitransparent glazes, and finally transparent varnish.

Although a variety of technologies is used to detect forgeries or alterations of such works of art, some of the technologies might damage the paintings or not be sensitive enough to detect finer details.

In the new study, the scientists utilized a medical technique called Optical Coherence Tomography that is used to produce three-dimensional images of the layers of the retina.

They said they used OCT to analyze two oil paintings from the 18th and 19th centuries. In one, "Saint Leonard of Porto Maurizio," OCT revealed evidence that the inscription "St. Leonard" was added approximately fifty years after completion of the painting. In the other, "Portrait of an unknown woman," OCT found evidence of the possible forgery of the artist's signature.

The research is detailed in the journal Accounts of Chemical Research.