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Objective: Magnetic fluid hyperthermia is a technique in which thermal energy is generated by magnetic nanoparticles (MNPs) that are excited by an alternating magnetic field (AC field). During hyperthermia, in-vivo monitoring of elevation of temperature relies on invasive insertion of conventional thermometers, or employment of thermo-sensitive cameras that lack high precision. The objective of this manuscript is to provide a mathematical approach to better estimate elevation of temperature and its profile after hyperthermia of MNPs inside an AC field. Methods: To this end, we first show that temperature profile due to hyperthermia of iron oxide MNPs at 10, 25, and 50 mg/ml are concentration dependent. Then by using best-fit polynomial equations, we show that the temperature profile for any given concentration of the same iron oxide MNPs can be traced to close approximation. Thermodynamic heat transfer equations were then used to graph the distribution of temperature in a tissue with a known heat capacity and conductivity parameters. Results: The resulting MatLab software simulation provides the thermal profile of a hypothetical tumor placed adjacent to a muscle tissue. Conclusions: In conclusion, the proposed mathematical approach can closely estimate the temperature profile of magnetic fluid hyperthermia.

We propose a new approach to microwave breast tumor sensing and diagnosis based on the use of biocompatible flagellated magnetotactic bacteria (MTB) adapted to operate in human microvasculature. It has been verified experimentally by Martel et al. that externally generated magnetic gradients could be applied to guide the MTB along preplanned routes inside the human body, and a nanoload could be attached to these bacterial microbots. Motivated by these useful properties, we suggest loading a nanoscale microwave contrast agent such as carbon nanotubes (CNTs) or ferroelectric nanoparticles (FNPs) onto the MTB in order to modify the dielectric properties of tissues near the agent-loaded bacteria. Subsequently, we propose a novel differential microwave imaging (DMI) technique to track simultaneously multiple swarms of MTB microbots injected into the breast. We also present innovative strategies to detect and localize a breast tissue malignancy and estimate its size via this DMI-trackable bacterial microrobotic system. Finally, we use an anatomically realistic numerical breast phantom as a platform to demonstrate the feasibility of this tumor diagnostic method.

Magnetic Resonance Navigation (MRN) relies on the use of an upgraded clinical Magnetic Resonance Imaging (MRI) scanner to navigate therapeutic, imaging, or diagnostic magnetic micro-agents in the vascular network. Although the high homogeneous field in the tunnel of the MRI scanner increases the magnetization of the navigable agents towards full saturation, the magnetic gradients superposed on such a high homogeneous field, generated by the Imaging Gradient Coils (IGC) typically used for MR-image slice selection, allow the induction of pulling forces to steer such agents in the targeted branches at the vessel's bifurcations. However, increasing the magnitude of such gradients leads to a significant decrease of the duty cycle, leading to a substantial reduction of the effective steering force being applied. To increase such a duty cycle, a Steering Gradient Coils (SGC) assembly capable of higher magnitudes while maintaining a 100% duty cycle can be installed at the cost of a much slower slew rate. Here, the use and the potential effectiveness of IGC and/or SGC for guiding such agents are briefly investigated on the basis of known specifications and experimental data.

The delivery of drug molecules to tumor hypoxic areas could yield optimal therapeutic outcomes. This suggests that effective cancer-fighting micro- or nanorobots would require more integrated functionalities than just the development of directional propelling constructs which have so far been the main general emphasis in medical micro- and nanorobotic research. Development of artificial agents that would be most effective in targeting hypoxic regions may prove to be a very challenging task considering present technological constraints. Self-propelled, sensory-based and directionally-controlled agents in the form of Magnetotactic Bacteria (MTB) of the MC-1 strain have been investigated as effective therapeutic nanorobots in cancer therapy. Following computer-based magnetotactic guidance to reach the tumor area, the microaerophilic response of drug-loaded MC-1 cells could be exploited in the tumoral interstitial fluid microenvironments. Accordingly, their swimming paths would be guided by a decreasing oxygen concentration towards the hypoxic regions. However, the implementation of such a targeting strategy calls for a method to switch from a computer-assisted magnetotactic displacement control to an autonomous aerotactic displacement control. In this way, the MC-1 cells will navigate to tumoral regions and, once there, target hypoxic areas through their microaerophilic behavior. Here we show not only how the magnitude of the magnetic field can be used for this purpose but how the findings could help determine the specifications of a future compatible interventional platform within known technological and medical constraints.