Analyzing magnetic nanoparticle content in biological samples: Acsusceptometry using offset fields

The clinical application of magnetic nanoparticles is a developing field with promising perspectives in treatment and diagnosis [1]. After the first applications as a contrast agent in MRI, other magnetic methods have been developed for excitation and detection of magnetic nanoparticles. For magnetic detection, the nonlinear behavior of superparamagnetic iron oxides provide excellent contrast in the linear magnetic human body. To exploit these properties, the design of magnetic nanoparticles as well as detection systems has to be optimized for clinical practice. The particles have to provide optimal sensitivity in contrast to tissue, whereas the signal-to-noise ratio and applicability of a measurement system are important for successful clinical implementation. In this contribution a setup is presented that is able to assess these both elements for sentinel lymph node mapping. Small intact biological samples, such as lymph nodes, can be measured at room temperature to characterize the magnetic nanoparticle content by differential magnetometry. Furthermore, the system can be used as a tool to analyze the magnetic properties of nanoparticles, providing insight in the quality for nonlinear particle detection.