Researchers have developed a way to measure the brain's precise temperature with a device only as thick as a poker-chip and which rests on a patient's head, eliminating the necessity of insertion.

The doctors also suggest that an injured brain can be significantly warmer than the body, a finding critical to cooling therapies that reduce brain damage in everyone from elderly heart attack victims to hypoxic (lacking oxygen) newborns.

"This is the first time that anyone has presented data on the brain temperature of a human obtained non-invasively," said principal researcher Thomas Bass, professor and neonatologist at Children's Hospital of The King's Daughters in Norfolk.

Hypoxic brain damage in infants occurs most often in full-term births when the child suffers oxygen loss either immediately before or during delivery, according to a Children's Hospital statement.

Because of a quirk in the brain, a child can be revived but brain cells continue to die over several days, resulting in brain damage or death.

Doctors could do little to stop this progression - parents often watched helplessly as their sons and daughters literally died before their eyes.

A research team led by Professor Bass, who pioneered research on cooling therapy for hypoxic newborns, adapted an instrument that calculates temperatures by detecting microwave emissions produced by all human tissues.

Those microwaves pass unimpeded through the skull, like light passing through a sheet of glass. As tissue temperatures increase, the emissions grow more intense.