Spatial quantitative information about magnetic nanoparticle (MNP) distributions is a prerequisite for biomedical applications like magnetic hyperthermia and magnetic drug targeting. This information can be gathered by means of magnetorelaxometry (MRX) imaging, where the relaxation of previously aligned MNP’s magnetic moments is measured by sensitive magnetometers and an inverse problem is solved. To remove or minimize the magnetic shielding in which MRX imaging is carried out today, the knowledge of the influence of background magnetic fields on the MNP’s relaxation is a prerequisite. We show MRX measurements using an intensity-modulated optically pumped magnetometer (OPM) in background magnetic fields of up to $100~\upmu \mbox{T}$ . We show that the relaxation parameters alter or may be intentionally altered significantly by applying static fields parallel or antiparallel to the MNP’s alignment direction. Further, not only the relaxation process of the MNP’s magnetic moments could be measured with OPM, but also their alignment due to the MRX excitation field.

中文翻译：

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存在直流偏置磁场的OPM磁弹性法

有关磁性纳米颗粒（MNP）分布的空间定量信息是生物医学应用（如磁性热疗和磁性药物靶向）的前提条件。此信息可以通过磁弹性法（MRX）成像收集，其中以前对准的MNP磁矩的弛豫由灵敏的磁强计测量，并且可以解决反问题。为了消除或最小化当今进行MRX成像的磁屏蔽，必须了解背景磁场对MNP弛豫的影响。我们显示了使用强度调制的光泵磁强计（OPM）在最高$ 100〜\ upmu \ mbox {T} $的背景磁场中进行MRX测量。我们表明，通过应用与MNP的排列方向平行或反平行的静态场，弛豫参数会发生改变或有意被显着改变。此外，不仅可以使用OPM来测量MNP磁矩的弛豫过程，而且可以通过MRX励磁场来测量它们的对准。