FOOTBALL teams of the future — even high school squads on limited budgets — may someday have a new tool to check players for brain injuries. It’s a special form of headgear, packed with sensors that read the brain waves of athletes after they come off the field, thus detecting changes caused by the trauma of hard knocks.

The compact, portable sensors decipher neural activity by measuring changes in the brain’s tiny magnetic field. These small magnetometers — still in the laboratory and in prototype — have yet to be tried on athletes. But their potential is enormous for brain imaging and for inexpensive monitoring of brain diseases, as well as for many other applications like the control of prosthetics, said Dr. José Luis Contreras-Vidal, a professor of electrical and computer engineering at the University of Houston.