Sentinel lymph node biopsy using magnetic nanoparticles: Towards implementation in laparoscopic surgery

The overall aim of this thesis is to explore the usage of magnetic nanoparticles for sentinel lymph node biopsies in the abdomen, and further develop a new magnetic detection prototype for laparoscopic surgery. The central medical problem which a sentinel lymph node biopsy (SLNB) tries to solve can be split into two parts. First, when a primary tumour is surgically treated by radical removal of the tumour and surrounding lymph nodes (LNs), unneeded tissue damage is caused if all removed LNs did not contain tumour cells. Second, if tumour cells spread to LNs outside the selected resection area, chance of tumour recurrence is high, leading to a worse patient prognosis. By using a tracer to select the primary draining lymph nodes (sentinel lymph nodes, SLNs) and removing those regardless of the anatomical area, less tissue damage is expected but with still a high accuracy to detect possible tumour cells. The used tracer in this thesis consists of superparamagnetic iron oxide nanoparticles. With a magnetic core and polymer coating, the tracer is seen as inert by the human body and is encapsuled by white blood cells in LNs, resulting in a good biocompatibility. The main parameter of interest of this tracer is it superparamagnetic (nonlinear) magnetic behaviour. Because of this, it is possible to automatically remove linear signals (e.g. surgical steel and the human body) with the used differential magnetometry method. To find this tracer, a magnetometer is necessary. Currently, there is only one commercially available magnetometer, which senses magnetic tracer, surgical steel and even the human body. To compensate, manual balancing between every measurement is necessary, which is time consuming. A novel magnetometer is further developed and described in this thesis which does not need balancing and can also be used during laparoscopic surgery. This thesis successfully demonstrates ways of using magnetic nanoparticles for SLNB. It also describes the development of a novel prototype for laparoscopic magnetic detection