Carlton Hayden, Ivkov Robert
Department of Radiation Oncology and Molecular Radiation Sciences, Johns Hopkins University School of Medicine, Baltimore, Maryland 21231, USA.
J Appl Phys. 2023 Jan 28;133(4):044302. doi: 10.1063/5.0131058. Epub 2023 Jan 27.
Heating magnetic nanoparticles (MNPs) with alternating magnetic fields (AMFs) have applications in biomedical research and cancer therapy. Accurate measurement of the heating efficiency or specific loss power (SLP) generated by the MNPs is essential to assess response(s) in biological systems. Efforts to develop standardized equipment and to harmonize results obtained from various MNP samples and AMF systems have met with little success. Without a standardized magnetic nanoparticle or calorimeter device, objective comparisons of estimated thermal output among laboratories remain a challenge. In addition, the most widely used adiabatic initial slope model fails to account for thermal losses, which are unavoidable. We propose a non-adiabatic method to analyze MNP heating efficiency derived from the Box-Lucas equation, wherein the sample is subjected to several short duration heating pulses. SLP is then estimated from an arithmetic average of the Box-Lucas fitted coefficients obtained from each pulse. Heating experiments were conducted with two identical samples that were placed within vessels having different thermal insulation using the same AMF parameters. Though the samples generated different temperature curves, the pulsed Box-Lucas method produced nearly equivalent SLP estimates. Further, the pulsed test enabled analysis of the heat transfer coefficient providing quantitative measures of sample heat loss throughout the test, with robust statistical confidence. We anticipate this new methodology will aid efforts to standardize measurements of MNP heating efficiency, enabling direct comparison among varied systems.
用交变磁场（AMF）加热磁性纳米颗粒（MNP）在生物医学研究和癌症治疗中具有应用价值。准确测量MNP产生的加热效率或比损耗功率（SLP）对于评估生物系统中的反应至关重要。开发标准化设备以及协调从各种MNP样品和AMF系统获得的结果的努力收效甚微。如果没有标准化的磁性纳米颗粒或量热计设备，各实验室之间对估计热输出进行客观比较仍然是一项挑战。此外，最广泛使用的绝热初始斜率模型无法考虑不可避免的热损失。我们提出一种非绝热方法，用于分析从Box-Lucas方程导出的MNP加热效率，其中样品受到几个短持续时间的加热脉冲。然后根据从每个脉冲获得的Box-Lucas拟合系数的算术平均值来估计SLP。使用相同的AMF参数，对放置在具有不同热绝缘的容器中的两个相同样品进行加热实验。尽管样品产生了不同的温度曲线，但脉冲Box-Lucas方法产生的SLP估计值几乎相同。此外，脉冲测试能够分析传热系数，在整个测试过程中提供样品热损失的定量测量，具有可靠的统计置信度。我们预计这种新方法将有助于实现MNP加热效率测量的标准化，从而能够在不同系统之间进行直接比较。
