Analysis of the Distribution of Magnetic Fluid inside Tumors by a Giant Magnetoresistance Probe

Magnetic fluid hyperthermia (MFH) therapy uses the magnetic component of electromagnetic fields in the radiofrequency spectrum to couple energy to magnetic nanoparticles inside tumors. In MFH therapy, magnetic fluid is injected into tumors and an alternating current (AC) magnetic flux is applied to heat the magnetic fluid- filled tumor. If the temperature can be maintained at the therapeutic threshold of 42°C for 30 minutes or more, the tumor cells can be destroyed. Analyzing the distribution of the magnetic fluid injected into tumors prior to the heating step in MFH therapy is an essential criterion for homogenous heating of tumors, since a decision can then be taken on the strength and localization of the applied external AC magnetic flux density needed to destroy the tumor without affecting healthy cells. This paper proposes a methodology for analyzing the distribution of magnetic fluid in a tumor by a specifically designed giant magnetoresistance (GMR) probe prior to MFH heat treatment. Experimental results analyzing the distribution of magnetic fluid suggest that different magnetic fluid weight densities could be estimated inside a single tumor by the GMR probe.

磁流体热疗（Magnetic fluid hyperthermia, MFH）疗法利用射频频段电磁场的磁分量，将能量耦合至肿瘤内部的磁性纳米颗粒。在MFH疗法中，磁流体被注入肿瘤，随后施加交变磁通（alternating current, AC）以加热充满磁流体的肿瘤。若能将温度维持在治疗阈值42℃并持续30分钟及以上，即可杀伤肿瘤细胞。在MFH疗法的加热步骤前，分析注入肿瘤的磁流体分布是实现肿瘤均匀加热的核心评判标准，借此可确定所需外部交变磁通密度的强度与定位，从而在不损伤健康细胞的前提下杀伤肿瘤。本文提出了一种分析方法，可在MFH热处理前通过特制巨磁阻（Giant magnetoresistance, GMR）探针检测肿瘤内的磁流体分布。针对磁流体分布的实验分析结果表明，通过该GMR探针可估算单颗肿瘤内不同的磁流体重量密度。