When you suspect a fever, you pop a thermometer in your mouth and take your temperature. In diseases such as Alzheimer's and Parkinson's, no simple tool can identify its biological traces. Now hope is emerging from an unexpected source: lasers. A new study suggests that a laser technique thought to be safe in humans can identify the telltale protein clumps that accumulate in these disorders.

Amyloid fibrils, which are dense buildups of abnormally folded proteins, occur in many neurological diseases. Currently the only way to detect them in the brain is during a postmortem dissection or using highly expensive PET scans. The new study, published in the December 2013 issue of Nature Photonics, uses a method called Z-scan spectroscopy to examine amyloid fibrils. The proteins' unusual structure appears to cause them to absorb more light than healthy tissue, which means a laser could theoretically detect their presence. Yet these are early days; we do not yet know if other proteins in the body could interfere with detection, according to Piotr Hanczyc, a chemist at the Chalmers University of Technology in Sweden, who led the study.

The current experiment used fibrils suspended in quartz, so the next step will be to extend the technique to living tissue. If scientists can pull it off, this method could represent a major advance in the diagnosis of these diseases, according to Daofen Chen, a program director at the National Institute of Neurological Disorders and Stroke. “You could intervene earlier,” Chen says. “That would provide a huge benefit.