Sebastiaan Waanders

A handheld SPIO-based sentinel lymph node mapping device using differential magnetometry

Sentinel lymph node biopsy has become a staple tool in the diagnosis of breast cancer. By replacing the morbidity-plagued axillary node clearance with removing only those nodes most likely to contain metastases, it has greatly improved the quality of life of many breast cancer patients. However, due to the use of ionizing radiation emitted by the technetium-based tracer material, the current sentinel lymph node biopsy has serious drawbacks. Most urgently, the reliance on radioisotopes limits the application of this procedure to small parts of the developed world, and it imposes restrictions on patient planning and hospital logistics. Magnetic alternatives have been tested in recent years, but all have their own drawbacks, mostly related to interference from metallic instruments and electromagnetic noise coming from the human body. In this paper, we demonstrate an alternative approach that utilizes the unique nonlinear magnetic properties of superparamagnetic iron oxide nanoparticles to eliminate the drawbacks of both the traditional gamma-radiation centered approach and the novel magnetic techniques pioneered by others. Contrary to many other nonlinear magnetic approaches however, field amplitudes are limited to 5 mT, which enables handheld operation without additional cooling. We show that excellent mass sensitivity can be obtained without the need for external re-balancing of the probe to negate any influences from the human body. Additionally, we show how this approach can be used to suppress artefacts resulting from the presence of metallic instruments, which are a significant dealbreaker when using conventional magnetometry-based approaches.

SPIO requirements for in vivo sentinel lymph node localization

Magnetic detection of sentinel lymph nodes using superparamagnetic iron oxide nanoparticles (SPIONs) is rapidly proving itself as a replacement technique for the logistically complex radioisotope-based standard of care. However, the SPIONs currently used in the magnetic procedure are chosen based purely on commercial availability. In this research, we evaluated three iron oxide based nanoparticles on both their magnetic characteristics and their performance in an in vivo porcine model, to illustrate that particle properties should be tailored for the application.

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.

Finding the Sentinel Lymph Node with a handheld differential magnetometer

In cancer staging, the Sentinel Lymph Node (SLN) procedure is a common method to assess the stage to which a cancer has progressed[1]. Currently, the SLN procedure is performed by injecting both a blue dye and a radionuclide tracer near or into the tumor area, and the first lymph node(s) draining the tumor area are located by means of visual inspection and a gamma probe which detects the radiation emitted by the radionuclide tracer. This combined procedure has proven to be very reliable and is used frequently, but suffers from some serious drawbacks that limit its applicability in general practice. These problems are mostly caused by the usage of ionizing radiation, which poses occupational hazards to medical staff and requires extensive logistics, which not all hospitals can offer.