SQUID Magnetometry for Cancer Screening a Feasibility Study

The recent demonstration that nanoparticles associated with various biological molecules and pharmacological agents can be administered systemically to humans, without toxicity from the particles, has opened a new era in the targeting of such particles to specific tissues in the body for the imaging and therapy of disease. The majority of particles used for this purpose contain iron and are detected in the body by magnetic resonance imaging. We believe a superconducting quantum interference device (SQUID) could provide quantitative and spatial information relevant to localization of superparamagnetic nanoparticles directed to a specific cell target in vivo. We envision a scanning system consisting of a DC induction field, a transport device, and an array of planar first order gradiometer coils coupled to DC SQUID amplifiers. We performed a set of computer simulations using experimentally determined values for concentrations of paramagnetic particles achievable in specific tissues of the mouse in vivo and concentrations of particles linked to monoclonal antibodies specific to antigens of two human cancer cell lines in vitro. An instrument to target distance of 10 centimeters was selected so that for an average adult scanning both the anterior and posterior surfaces could provide coverage of most of the body. The simulations demonstrate the feasibility of SQUID magnetometry for monitoring achievable concentrations of superparamagnetic particles in vivo and raise the possibility of using this approach to detect and localize collections of abnormal cells targeted by such particles.