A method for use and an improved oximeter sensor substrate that is conforming to the shape of the patient's forehead. In one embodiment, the present invention is an oximeter sensor, having a substrate with a shape similar to a shape of at least a portion of a patient's forehead and including a section adapted to substantially fit over a portion of a forehead of a patient; an emitter disposed on the substrate at a position located on the section; and a detector disposed on the substrate at a distance from the emitter. In one embodiment, the substrate includes a hat that holds the emitter and the detector in a spaced-part manner against the patient's forehead.