Laser light in combination with certain drugs – known as photodynamic therapy – can destroy cancer tumors. But, this method is currently used mostly to cure skin cancer. The reason that internal tumors are not treated with photodynamic therapy is that the technology does not exist to check that the precise amount of light is administered. However, software developed by researchers in atomic physics at Lund University in Sweden looks like it may solve the problem. The software’s unique feature is that it uses optical fibres for more than simply emitting light. Intermittently, they also gather information about the tumor, which they send back to the laser instrument. According to the researchers, the software could also be used with other light therapies that use LEDs or infra-red lasers.