Atomic magnetometers (AM) and magnetic nanoparticle (MNP) samples — both in water–suspended solutions and in a blocked state — are at the heart of this Ph.D. thesis. On one hand, I have developed, constructed and characterized different types of atomic magnetometers and operation modes thereof. On the other hand, I have developed complex coil systems for generating and scanning both homogeneous and strongly inhomogeneous magnetic fields. The aim of the thesis was to demonstrate that AM methods can be used to detect, quantify, characterize and image MNP distributions.
Biomedical applications of MNPs have been rapidly evolving over the past decade, and many methods have been well established, while new techniques appear in the literature on a monthly, if not weekly, basis. The Fribourg group for Atomic Physics (FRAP) in whose labs the presented work was carried out has an internationally–recognized competence in the modeling, development and applications of atomic magnetometers. Since many MNP applications rely on the detection of the magnetic field produced by the MNPs, FRAP devotes most of its current research activity to explore whether detection of that field by AM methods offers advantage(s) over conventional/established detection methods.
The main experimental challenge that had to be surmounted is the fact that magnetizing the particles requires magnetic flux densities in the mT–range, while the flux density at the AM position is some 6–8 orders of magnitude weaker. To this adds a second obstacle, namely the use of strong magnetic field gradients (order of T/m) at the MNP position, and the necessity of their suppression at the AM site. In this talk I address the underlying concepts of the detection and imaging of MNP samples as well as the individual steps that leaded to the demonstration of an AM-based 2D magnetic nanoparticle imaging (MPI) scanner. In particular, I show that AMs can access signals in a different (lower) frequency band compared to established method being thus, in many applications, complementary to the latter.