Jung Kyung Kim

Effect of tumor properties on energy absorption, temperature mapping, and thermal dose in 13.56-MHz radiofrequency hyperthermia

Computational techniques can enhance personalized hyperthermia-treatment planning by calculating tissue energy absorption and temperature distribution. This study determined the effect of tumor properties on energy absorption, temperature mapping, and thermal dose distribution in mild radiofrequency hyperthermia using a mouse xenograft model. We used a capacitive-heating radiofrequency hyperthermia system with an operating frequency of 13.56u202fMHz for in vivo mouse experiments and performed simulations on a computed tomography mouse model. Additionally, we measured the dielectric properties of the tumors and considered temperature dependence for thermal properties, metabolic heat generation, and perfusion. Our results showed that dielectric property variations were more dominant than thermal properties and other parameters, and that the measured dielectric properties provided improved temperature-mapping results relative to the property values taken from previous study. Furthermore, consideration of temperature dependency in the bio heat-transfer model allowed elucidation of precise thermal-dose calculations. These results suggested that this method might contribute to effective thermoradiotherapy planning in clinics.

Computational fluid dynamics of impinging microjet for a needle-free skin scar treatment system

A needle-free injection system is a non-invasive drug delivery system, and its applications are currently being extended from the delivery of vaccines and insulin. At present, they are gaining considerable popularity in skin remodeling treatment techniques, particularly in skin rejuvenation procedures involving the injection of aesthetic materials. Although some clinical studies have been conducted to understand the mechanisms involved in these practices, an extensive study from an engineering point of view has not yet been conducted. Herein, we aim to identify the key parameters in the needle-free injection process and study their effects on microjet characteristics. The total stagnation pressure of an impinging microjet determines the penetration capabilities of the injection and is monitored with the aid of both experimental and computational tools employed on a typical commercial injector. Our findings indicated that the filling ratio and driving pressure had significant impacts on the peak and average stagnation pressures of the impinging microjet. Furthermore, the penetration characteristics of a standard nozzle and injection fluid could be controlled by an effective combination of the filling level and driving pressure, and thus, they can be considered as vital parameters when performing skin remodeling procedures.

Temperature mapping and thermal dose calculation in combined radiation therapy and 13.56 MHz radiofrequency hyperthermia for tumor treatment

To evaluate the synergistic effect of radiotherapy and radiofrequency hyperthermia therapy in the treatment of lung and liver cancers, we studied the mechanism of heat absorption and transfer in the tumor using electro-thermal simulation and high-resolution temperature mapping techniques. A realistic tumor-induced mouse anatomy, which was reconstructed and segmented from computed tomography images, was used to determine the thermal distribution in tumors during radiofrequency (RF) heating at 13.56 MHz. An RF electrode was used as a heat source, and computations were performed with the aid of the multiphysics simulation platform Sim4Life. Experiments were carried out on a tumor-mimicking agar phantom and a mouse tumor model to obtain a spatiotemporal temperature map and thermal dose distribution. A high temperature increase was achieved in the tumor from both the computation and measurement, which elucidated that there was selective high-energy absorption in tumor tissue compared to the normal surrounding tissues. The study allows for effective treatment planning for combined radiation and hyperthermia therapy based on the high-resolution temperature mapping and high-precision thermal dose calculation.

Enhanced Particle Detection in a Spinning Helical Microchannel

The present study is focused on developing a CD4+ T-cell counting device for HIV/AIDS monitoring with the aid of a helical microchannel. Numerical studies were carried out in a stationary and a spinning helical microchannel to compare the effect of pressure drop and flow distribution for a high pressure and varying spinning speed and thereby stable conditions for the experiment was derived out. For the experiment, 10 μm sized particles were used for visualization with a fluorescence microscope system. A sample with the viscosity as that of blood and other samples with different viscosities were also prepared to determine the effect of density and viscosity in aligning the particles. The samples were then injected into the channel and the particles were then traced in stationary and spinning channels. The channels were rotated using a DC motor controlled by an Arduino board with a Bluetooth shield. It was found that when the sample cartridge was made stationary, no particle alignment was achieved for a medium with density lower than that of the particles, but when it was spun at 2000–3000 rpm for 1–4 min, an alignment was obtained at the top of the channel facilitating detection of those particles. Since an alignment of particles was achieved for a medium with density as that of blood plasma, the same approach can be applied for aligning and counting CD4+ T-lymphocytes in whole blood samples collected from patients.