Characterization of superparamagnetic iron oxide nanoparticles in biological environments

Characterization of superparamagnetic iron oxide nanoparticles on biological environment

Separation of excitation and detection coils to locate superparamagnetic iron oxide nanoparticles in vivo

The aim of this study is to develop a novel laparoscopic probe for sentinel node biopsy. The latter is a procedure to analyze the lymph node status of cancer patients [1], enabling personalized patient care

Separation of excitation and detection coils for in vivo detection of superparamagnetic iron oxide nanoparticles

A novel probe for laparoscopic in vivo detection of superparamagnetic iron oxide nanoparticles (SPIONs) has been developed. The main application for in vivo detection of SPIONs our research group aims at is sentinel node biopsy. This is a method to determine if a tumor has spread through the body, which helps to improve cancer patient care. The method we use to selectively detect SPIONs is Differential Magnetometry (DiffMag). DiffMag makes use of small magnetic field strengths in the mT range. For DiffMag, a handheld probe is used that contains excitation and detection coils. However, depth sensitivity of a handheld probe is restricted by the diameter of the coils. Therefore, excitation and detection coils are separated in our novel probe. As a result, excitation coils can be made large and placed underneath a patient to generate a sufficiently large volume for the excitation field. Detection coils are made small enough to be used in laparoscopic surgery. The main challenge of this setup is movement of detection coils with respect to excitation coils. Consequently, the detector signal is obscured by the excitation field, making it impossible to measure the tiny magnetic signature from SPIONs. To measure SPIONs, active compensation is used, which is a way to cancel the excitation field seen by the detection coils. SPIONs were measured in various amounts and at various distances from the excitation coils. Furthermore, SPIONs were measured in proximity to a surgical steel retractor, and 3 L water. It is shown that small amounts of SPIONs (down to 25 μg Fe) can be measured, and SPIONs can be measured up to 20 cm from the top of the excitation coil. Also, surgical steel, and diamagnetism of water – and thus of tissue – have minor influence on DiffMag measurements. In conclusion, these results make this novel probe geometry combined with DiffMag promising for laparoscopic sentinel node biopsy

Differential magnetometry to detect sentinel lymph nodes in laparoscopic procedures

Differential Magnetometry to detect sentinel lymph nodes in laparoscopic procedure

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. © 2013 IEEE