Magnetic nanoparticle heating and heat transfer on a microscale: Basic principles, realities and physical limitations of hyperthermia for tumour therapy

In this review article, we present basic principles of magnetically induced heat generation of magnetic nanoparticles for application in magnetic particle hyperthermia. After explanation of heating mechanisms, the role of particle-particle as well as particle-tissue interactions is discussed with respect to achievable heating power of the particles inside the tumor. On the basis of heat transfer theory at the microscale, the balance between generated and dissipated heat inside the tumor and the resulting damaging effects for biological tissue is examined. The heating behavior as a function of tumor size is examined in combination with feasible field strength and frequency. Numerical calculations and experimental investigations are used to show the lower tumor size limit for tumor heating to therapeutically suitable temperatures. In summary, this article illuminates practical aspects, limitations, and the state of the art for the application of magnetic heating in magnetic particle hyperthermia as thermal treatment of small tumors.