A system for estimating the brain blood volume and/or brain blood flow and/or depth of anesthesia of a patient, comprising: - at least one excitation electrode to be placed on a temple of the head of a patient for applying an excitation signal, - at least one sensing electrode to be placed on a temple of the head of the patient for sensing a measurement signal caused by the excitation signal, - at least one electrode to be placed on the scalp of the patient's head to receive an EEG signal of spontaneous electrical activity of the brain of the patient, and - a processor device for processing said measurement signal sensed by the at least one sensing electrode in a first processing path comprising an amplification device for amplifying the measurement signal and an analog-to-digital converter for digitizing the measurement signal, for determining an output indicative of the brain blood volume and/or the brain blood flow, wherein the processor device is constituted to reduce noise in the measurement signal by applying a non-linear noise-reduction algorithm, and the processor device is constituted to determine, based on the noise-reduced version of the measurement signal, a correlate of the brain blood volume according to an area obtained from integration of the measurement signal, wherein the area is obtained from integration of the measurements signal over the LVTE period, which is estimated as the period from a point, defined as the minimum of the derivative of voltage curve prior to a maximum point, to a point, defined as the minimum of the derivative of the voltage curve immediately after said maximum point, and wherein the processor device is constituted to determine a correlate of the brain blood flow by multiplying said correlate of the brain blood volume with a value indicative of the heart rate of the patient, wherein the processor device is constituted to feed the correlate of the brain blood volume and/or the correlate of the brain blood flow into a first non-linear model to obtain output values indicative of the brain blood volume and/or the brain blood flow, wherein the processor device is constituted to feed said output values and features derived from the EEG signal, via a second processing path of the processor device, into a second non-linear model to obtain final output values for the brain blood volume and/or the brain blood flow, and/or an output value indicative of a depth of anesthesia. - at least one excitation electrode to be placed on a temple of the head of a patient for applying an excitation signal, - at least one sensing electrode to be placed on a temple of the head of the patient for sensing a measurement signal caused by the excitation signal, - at least one electrode to be placed on the scalp of the patient's head to receive an EEG signal of spontaneous electrical activity of the brain of the patient, and - a processor device for processing said measurement signal sensed by the at least one sensing electrode in a first processing path comprising an amplification device for amplifying the measurement signal and an analog-to-digital converter for digitizing the measurement signal, for determining an output indicative of the brain blood volume and/or the brain blood flow, the processor device is constituted to reduce noise in the measurement signal by applying a non-linear noise-reduction algorithm, and the processor device is constituted to determine, based on the noise-reduced version of the measurement signal, a correlate of the brain blood volume according to an area obtained from integration of the measurement signal, wherein the area is obtained from integration of the measurements signal over the LVTE period, which is estimated as the period from a point, defined as the minimum of the derivative of voltage curve prior to a maximum point, to a point, defined as the minimum of the derivative of the voltage curve immediately after said maximum point, and wherein the processor device is constituted to determine a correlate of the brain blood flow by multiplying said correlate of the brain blood volume with a value indicative of the heart rate of the patient, wherein the processor device is constituted to feed the correlate of the brain blood volume and/or the correlate of the brain blood flow into a first non-linear model to obtain output values indicative of the brain blood volume and/or the brain blood flow, wherein the processor device is constituted to feed said output values and features derived from the EEG signal, via a second processing path of the processor device, into a second non-linear model to obtain final output values for the brain blood volume and/or the brain blood flow, and/or an output value indicative of a depth of anesthesia.