Hyperthermia is a non-invasive localized heating technique that has proven to be an efficient cancer treatment method. Hyperthermia therapy needs precise temperature control to ensure delivery of the proper thermal dose, causing minimum damage to the neighboring healthy tissues. This work reports the indigenous development of a custom-designed hyperthermia instrument. An advanced RISC machine (ARM)-based embedded closed-loop proportional-integral (PI) controller is developed for controlling the temperature. As per the applied methodology, the DC bias of a Mazzilli oscillator-based half-bridge inverter is controlled through the controller. The PI controller reads the hyperthermia system temperature using an infrared (IR) radiation thermometer and generates an analog output accordingly. This, in turn, changes the amplitude of the alternating magnetic field (AMF), thus controlling the temperature of the magnetic nanoparticles (MNPs). Its potential has been explored for in vitro hyperthermia studies. In vitro experiments have been carried out successfully with the custom-designed heater and controller assembly utilizing commercial non-invasive temperature measurement with a standard deviation of about 0.3°C and overshoot within the hyperthermia temperature range (3°C). The developed system has also obtained a satisfactory value of specific absorption rate (SAR). This paper infers the feasibility of the indigenously developed circuit and the related controller for hyperthermia therapy and preclinical studies. This system can be used for clinical applications with suitable customizations.
Keywords: Magnetic hyperthermia; Mazzilli inverter; PI control; infrared (IR) radiation thermometry.
This paper reports an indigenously developed complete magnetic hyperthermia instrument including a custom-designed driving circuit with real-time embedded proportional-integral (PI) control and non-invasive infrared (IR) thermometry. This developed instrument has been tested with two planar coils in different frequencies (199 to 290 kHz) and the system performance has also been presented here. This paper establishes the feasibility of the development of an integral system with a versatile inductive driver circuit, indigenous coil, and PI controller for hyperthermia applications. This system can be used for non-invasive, superficial tissue temperature control in hyperthermia therapy or preclinical hyperthermia studies. If the fiber-based sensor is used in place of IR thermometer, the proposed induction heater assembly, along with the temperature controller, can be used for deep tissue hyperthermia as well.