Superconducting magnetometer system for detecting lung contaminants

We describe a superconducting magnetometer system for the detection and measurement of ferrimagnetic contaminants or tracer materials in the lungs. This technique, known as magnetopneumography (MPG), offers a non-invasive, passive means to investigate lung clearance mechanisms using inhaled biologically inert magnetic tracers or to measure some potentially toxic air-borne particulates due to environmental or occupational sources. The MPG system consists of two principal components, a SQUID magnetometer and a superconducting magnet, each with its own liquid helium dewar. The response of the system is a function of both the magnetizing field and the field sensitivity of the SQUID detection coils. The SQUID magnetometer has a sensitivity of less than 700 fT (1 fT = 10^-15Tesla). The equivalent system noise in terms of particulate contaminants is less than one microgram of total ferrimagnetic particulates dispersed uniformly throughout in the lungs. The MPG system described has an order of magnitude better sensitivity than any previously constructed system, and has the ability to detect relaxation phenomena with time constants as short as 10 seconds. This is expected to assist in the understanding of lung clearance mechanisms.