Portable devices with painless laser beams could soon replace X-rays as a non-invasive way to diagnose disease.

带有无痛激光束的便携设备可能将迅速取代X射线成为诊断疾病得力工具。

Researchers say that the technique could become widely available in about five years.

The method, called Raman spectroscopy（光谱学） , could help spot the early signs of breast cancer, tooth deca（蛀牙，龋齿） and osteoporosis（骨质疏松症） .

Scientists believe that the technology would make the diagnosis¹ of illnesses faster, cheaper and more accurate.

Raman spectroscopy is the measurement of the intensity² and wavelength³ of scattered⁴ light from molecules⁵.

It is already being used in the chemical and pharmaceutical⁶ industries. For instance, Raman lasers are used to measure flame characteristics. By studying how fuels burn, pollution from the products of combustion⁷（燃烧） can be minimised.

Michael Morris, a chemistry professor at the University of Michigan, US, has been using Raman for the past few years to study human bones.

So far, he has been working on cadavers⁸, but he says that Raman could prove effective in living patients.

"You can replace a lot of procedures, a lot of diagnostics that are out there right now. The big advantage is that it's non-invasive, pretty fast - much faster than classical procedures - and more accurate," he told BBC News.

When a person is sick, or about to become sick, the chemical mix in the tissue is quite different from that in healthy tissue, scientists say. So the Raman spectrum⁹ changes depending on the tissue it analyses, Professor Morris explained.

"Raman gives you a molecular¹⁰ fingerprint¹¹, a composition of whatever it is you're measuring," he said.

"In diseased states, the chemical composition is either slightly abnormal or very markedly（显著地） abnormal, depending upon the diseases."