Non-invasive measurement of blood flow using magnetic disturbance method

Current laser Doppler method of blood flow sensing requires optical contact to the skin, tend to be bulky and have performance subjective to body fluids (e.g. blood, perspiration) and environmental contaminants (e.g. mud, water). This paper proposes a novel method of noninvasive acquisition of blood flow by measuring the magnetic disturbance created due to blood flowing through a localized magnetic field. The proposed system employs a GMR based magnetic sensor and magnet of 3 mm radius, placed on a major blood vessel. The magnetic field generated by the magnet acts both as the biasing field for the sensor and also the uniform magnetic flux for blood flow disturbance. As such, the system is compact, operates at room temperature and is able to sense through clothing. The signal acquired from the magnetic and optical methods are compared using the post-occlusive reactive hyperaemia test, where measurement results on 6 different healthy subjects are found to have error of less than 5%, showing the successful use of the magnetic method to measure blood flow.