Significance Magnetic-induction hyperthermia, also known as magnetic hyperthermia, is an emerging physical-therapy modality for treating tumors clinically. It utilizes magnetic nanomaterials to generate heat under an alternating magnetic field (AMF), thereby triggering molecular events that selectively destroy tumor cells. Hyperthermia offers several advantages over conventional treatments such as chemotherapy and radiotherapy, including its minimal invasiveness, remote controllability, potential for repeatable treatments, and ability to induce anti-tumor immunity. These characteristics highlight the significant potential of magnetic hyperthermia in clinical tumor treatment. Over the recent decades, continuous effort has been expended to enhance the design of AMF generators, with emphasis on the integration of inverter and power-amplification technologies. However, comprehensive summaries regarding the development of AMF generators are insufficient. Therefore, an overview of currently used AMF generators is necessary to encourage the development of magnetic-hyperthermia devices for clinical applications. Progress This paper elucidates the operating principles, coil types, and strategies for optimizing the AMF characteristic parameters-such as frequency, field strength, and uniformity-of magnetic-hyperthermia generators. We review relevant magnetic-hyperthermia devices and summarize their advantages and disadvantages. AMF generators generate two types of magnetic fields, ie, coil and core types. The coil type uses various conductor configurations, such as spiral tubes, flat coils, and Helmholtz coils. By contrast, the core type involves a conductor wrapped around a magnetically conductive medium, such as ferrite, which transfers magnetic field energy and creates an AMF concentrated in the ferrite gap. Additionally, we introduce two magnetic-hyperthermia systems equipped with AMF focusing and waveform-transformation capabilities. Previous studies three utilized hollow spiral tubes as output terminals to construct a magnetic-hyperthermia system equipped with AMF focusing (Fig. 2). These systems address the problem of dispersed action ranges. Systems with waveform-transformation capabilities can be used to investigate the effects of different magnetic-field waveforms on the magneto-thermal efficiency of magnetic nanomaterials. Furthermore, we discuss a research platform that integrates optical testing instruments, ie, a confocal laser scanning microscope and spectrometer, with a magnetic-hyperthermia device. Researchers have designed small ferrite coils with narrow gaps for confocal laser scanning microscopes to realize a research platform (Fig. 3). Similarly, Helmholtz-like coils have been used in conjunction with a spectrometer to create platforms (Fig. 4). This integration provides a unique tool for performing comprehensive studies on the magnetic-hyperthermia effect at the molecular/cellular level. Additionally, this study reviews existing clinical magnetic-hyperthermia devices and discusses their potential clinical applications. These devices include the first prototype developed by Jordan's group in Germany, the NFH (R) 300F commercial magnetic-hyperthermia equipment developed by Gneveckow's group in Germany, and a third-generation equipment developed by Tang Jintian's group in China. Continuous technological advancements and optimizations are expected to enhance the therapeutic efficacy and prognosis of tumor physical therapy, thus rendering magnetic hyperthermia a crucial tool in future cancer treatments. Conclusions and Prospects Magnetic-hyperthermia devices are pivotal in advancing research and enhancing oncology treatments. Although most current devices are primarily used in cellular and animal experiments, their broader clinical application requires emphasis on several key points. First, magnetic-hyperthermia devices must be able to generate therapeutic magnetic fields suitable for the human body. Hence, low-loss, high-power coils with a wide spatial range must be developed. Second, to generate wide-ranging, high-intensity, and high-frequency magnetic fields, inverter-circuit components must withstand high voltages and currents. Accurate control systems are required to reduce power loss. Third, as equipment power increases, better cooling systems are necessitated for stability and safety improvement. Additionally, magnetic field-focused devices should minimize heat damage to normal tissues, thereby reducing side effects. Developing new generations of magnetic-hyperthermia devices will advance scientific research and provide a foundation for widespread clinical applications, thus potentially offering optimism for cancer treatment.
