Application and comparison of thermistors and fiber optic temperature sensor reference for ILP measurement of magnetic fluids in double cell magnetic hyperthermia.

One of the simplest way to characterize the heating efficiency of magnetic fluids used in hyperthermia treatment is the calorimetric measurement of the specific loss power with direct temperature detection. However, the performance of metallic sensors in an alternating magnetic field is degraded by the self-heating of the probes, and electromagnetic interference can be also significant. In our double cell differential thermometric system these disturbing effects can be compensated. Specific loss power measurements of EMG700 magnetic fluid with negative temperature coefficient thermistors in differential configuration are presented, and control measurements were performed with an optical fiber thermometer in f = 470 kHz - 1020 kHz frequency and H = 0.13 kA m - 1 - 1.19 kA m - 1 magnetic field strength range. We found that the specific loss power is proportional to the frequency and shows a quadratic dependence on the field strength in the low field strength region, therefore we calculated the intrinsic loss power of the fluid from the measured specific loss power. At this field conditions intrinsic loss power up to 0.53 nH m 2 kg - 1 was determined.

Magnetic field response of aqueous hydroxyapatite based magnetic suspensions.

During the biomedical and biotechnological applications of hydroxyapatite based magnetic biomaterials the response to various magnetic fields (i.e. change in flow behavior) plays a pivotal role in manipulating these materials. Numerous studies discuss the synthesis, characterization and possible applications of magnetic hydroxyapatite, however the number of reports related to the magnetic response is limited. In this study we investigated the response of aqueous suspensions of magnetite/hydroxyapatite composites with gelatin as an additive to homogeneous and inhomogeneous magnetic fields. Under homogeneous field the change in rheological properties was determined, and correlated with the composition of the composites. The effect of magnetite and gelatin content on the zero field viscosity and magnetic susceptibility were also evaluated. The response to inhomogeneous field was characterized by measuring the magnetic body force acting on droplets of the aqueous suspensions. We found that the formulation of the composites and the presence of additive largely affect the magnetic response.