You can read more information about crystals to measure brain damage at this site.  The military wants to use this for every soldier so there will be a reliable way to detect brain damage early.  This is beneficial because often brain damage may go undetected and thus untreated.  However, undetected brain damage can have many negative consequences for the individual even if it is nearly imperceptible.  These crystals will be able to detect the force of a blast from a bomb.  Often the shock wave of a bomb causes the brain to push against the skull and this may cause some damage.