Optimal design of bone tumor ablation device based on radio frequency heating using Taguchi method.

This study investigated the optimal design of a radio-frequency (RF) bone tumor ablation device to achieve uniform heating. In a previous study, we confirmed the feasibility of this device, which could heat all regions of the bone to 70 °C or higher and maintain this temperature for more than 30 min. However, the temperature in each part was non-uniform. To address this issue, the shape of the electrode must be modified to create a uniform electric field. The design of the electrode was optimized to reduce temperature deviations. It is difficult to analytically model the relationship between the shape of the electrode and the electric field. The electrode's design factors were fine-tuned using the Taguchi method, a robust design of experiment approach. The primary objective in this optimization was to maximize the signal-to-noise ratio for temperature in each component, aiming for higher values. After four trials, the signal-to-noise ratio increased in comparison with the initial modified shape from 68.3 to 98.6. The experiment was conducted using an experimental device fabricated using the optimal design factors. In comparison to the previous experiment, the temperature standard deviation per part over time decreased from 10.56 °C 4.28 °C. The experimental results demonstrated the validity of the proposed optimal design approach. In the future, the proposed method can be used to optimize the design factors when a product is advanced to develop a device that can be applied to the human body.

Effect of radio frequency energy on buckwheat quality: An insight into structure and physicochemical properties of protein and starch.

Radio frequency (RF) heating as an emerging technology is widely used to improve cereal-based food quality. To further investigate effects of RF treatment on buckwheat quality, structures and physicochemical properties of protein and starch in buckwheat were evaluated under various temperatures (80, 90, and 100 °C) and holding times (0, 5, and 10 min). Results showed that protein-starch complexes were reaggregated with the increases of RF heating temperature and time, as well as the values of R1047/1022, crystallinity, random coil, and α-helix significantly decreased, and the values of ß-sheet obviously increased. Moreover, viscosities and rheological properties of buckwheat were reduced by the raised RF treatment intensity. Besides, the RF processing had a mostly positive effect on swelling power at low temperature of 30 °C, but contrary effect at high temperatures of 60 °C and 90 °C. However, changes of water solubility index, emulsifying capacity, and emulsion stability depended on the RF processing intensity. These results of the study suggested that buckwheat quality was affected by multiple RF treatment conditions, which can be tailored to develop a RF process having the potential to improve the function of buckwheat flour.

Effects of sequential treatments using radio frequency energy and ultraviolet light on inactivation of Bacillus cereus spores and quality attributes of buckwheat.

Buckwheat kernels were susceptible to be contaminated by heat-resistant spores. This study aimed to investigate effects of radio frequency (RF) heating, ultraviolet (UV) light and their combination treatment on the inactivation of B. cereus spores and quality attributes of buckwheat kernels. Results showed that Weibull model well fitted the inactivation curves of B. cereus spores under RF heating or UV light, and both of the two techniques had a tailing phenomenon (n < 1) in the decontamination process. But the inactivation levels of spores significantly increased by the combined treatments of RF and UV, regardless of the treatment sequence. Treatment by individual RF heating at 105 °C for 30 min or UV exposure at 5.00 mW/cm2 for 60 min resulted in >2.0 log CFU/g reduction of B. cereus spores. The similar inactivation effect could be achieved with shorter processing times by combined treatments (RF temperature-holding time + UV intensity-irradiation time: 85-10 + 3.50-10, 90-0 + 2.25-10, and 95-5 + 1.00-10). Besides, the colors, antioxidant compounds and antioxidant activities of buckwheat were not significantly deteriorated after these combined treatments, but the enzymatic activities were reduced, which was beneficial for long-term storage. Therefore, the proposed sequential treatment of RF heating and UV light in this study holds great potential to assure the food safety of grains.

Gel properties and thermal gelling mechanism in myofibrillar protein of grass carp (Ctenopharyngodon idellus) under the synergistic effects of radio frequency combined with magnetic field.

This study evaluated the effects of radio frequency (RF)-replaced water bath (WB) or/and magnetic field (MF)-assisted WB heating on various quality parameters of grass carp myofibrillar protein (GCMP) gel and to understand the thermal gelling mechanism. Compared with the control, RF-replaced 40°C WB combining MF-assisted 80°C WB heating promoted GCMP structural changes, that was random coil content observably increased from 28.87% to 32.3% at the expense of α-helix reducing from 17.93% to 15.80%, even promoting the self-assembly of exposed residues. These structural changes were conducive to form relatively smooth and loose gel network structures, thus significantly increasing immobilized and bound water and improving water holding capacity. The electrostatic repulsion between exposed residues was conducive to the stability of protein molecules and gel structure. Overall, the RF-replaced 40°C WB combining MF-assisted 80°C WB heating was a desirable thermal alternative to conventional WB heating for improving gel quality.

Effect of Large-Scale Paddy Rice Drying Process Using Hot Air Combined with Radio Frequency Heating on Milling and Cooking Qualities of Milled Rice.

The objectives of the study on a continuous flow hot air dryer combined with radio frequency heating at different temperatures (HA/RF) (38 °C, 42 °C, 46 °C, and 50 °C) in a large-scale process compared with conventional continuous flow hot air drying (HA) were (1) to investigate the drying characteristics, drying kinetics, and milling quality of the process and (2) to observe the cooking quality and compare the sensory differences of the cooked rice after treatment. The drying characteristics and moisture diffusivity showed that the higher the radio frequency (RF) heating temperature, the shorter the drying time. The specific energy consumption and energy cost decreased when the RF heating temperature increased. The optimal condition in terms of fissure percentage was HA/RF42. In addition, there were no significant differences in head rice yield and white rice color determination, amylose content, texture profiles, and pasting properties in all HA/RF treatments. In the triangle test, it was found that at least 6% of the population could perceive a difference between HA and HA/RF50. In conclusion, this study proposes the further development of the HA/RF drying process at low-temperature profiles and shows the great potential of RF technology for commercial drying in rice industry.

Combined effects of intermittent radio frequency heating with cinnamon oil vapor on microbial control and quality changes of alfalfa seeds.

Alfalfa sprouts have high nutritional values when consumed raw, but are easily contaminated by food pathogens. This study aimed to evaluate effects of essential oil (EO) vapors, RF heating and their combinations on microbial inactivation, germination rate and generated sprouts' quality of alfalfa seeds at moisture contents of 7.52%, 9.53% and 11.45% wet basis (w.b.). Results showed that cinnamon oil and oregano oil vapors both had antimicrobial effects against Salmonella on alfalfa seeds and cinnamon oil vapor had a little better activity. Weibull model well fitted the Salmonella inactivation curves under RF heating. The rate of Salmonella inactivation increased but germination rate decreased with increasing temperature and moisture content of seeds. The intermittent RF treatments improved the heating uniformity and germination rate of the whole batch of seeds as compared to the continuous RF heating. The combination of intermittent RF heating and cinnamon oil vapor exhibited additive antimicrobial effects, up to 3.99-4.12 log CFU/g Salmonella reductions, and maintained the germination rate above 90%. However, for natural microbial decontamination, combined treatments only caused 0.56-0.82 log CFU/g reductions of total bacterial counts. The fresh weight, length, flavor, the content of phenolics and ascorbic acid, and antioxidant capacity of generated sprouts were not significantly impacted. The study provided an effective method for microbial control on sprouting seeds.

Hot air-assisted radio frequency drying of apricots: Mathematical modeling study for process design.

Conventional hot air and solar energy processes have been used for apricot. These processes had adverse effects on the quality due to the longer process times, and this indicates the need for an innovative approach. Radio frequency (RF) processing has innovation potential for drying with its volumetric heating feature, but an optimal process should be designed for process efficiency in industrial-scale applications. Therefore, the objective of this study was to confirm the RF process for industrial-scale apricot drying. For this purpose, a mathematical model was developed to predict temperature and moisture content change of apricots during drying, and experimental validation study was carried out. For the RF drying process, pre-dried apricots (0.58-0.75 kg water/kg dry matter, db) by solar energy were used. The purpose was to start the RF process at a suitable moisture content level as this process was not feasible to apply directly due to the high initial moisture content of apricots (up to 4 kg water/kg dry matter, db). RF drying experiments were carried out in a 10 kW hot air-assisted (50-60°C) staggered through electrode system. Optimum electrode gap was 81 mm with 2500 V potential of the charged electrode. Final moisture content of the dried apricots was 0.25-0.33 kg water/kg dry matter (db). Following the model validation for temperature and moisture content change, industrial-scale apricot drying scenarios were demonstrated to confirm the RF process for feasibility and process design. PRACTICAL APPLICATION: A comprehensive mathematical model was developed for radio frequency (RF) drying of apricots. This model was experimentally validated with respect to the temperature and moisture content change. Various process design studies were carried out for an industrial-scale apricot drying process to confirm the process feasibility. With this background, the results of this study can be directly used in an industrial drying for an optimal process design and energy efficiency.

Effects of radio frequency heating on microbial populations and physicochemical properties of buckwheat.

Microbial contamination is a persistent problem for grain industry. Many studies have shown that radio frequency (RF) heating can effectively reduce pathogens populations in low moisture foods, but there is a lack on the efficacy to decontaminate natural microbiome. The main objectives of this study were to investigate the effects of different RF heating conditions on natural microbial populations and physicochemical properties of buckwheat. In this study, 30 buckwheat samples collected from 10 different Provinces in China were analyzed for their microbial loads, and the samples with the highest microbial populations were used for further study to select the suitable RF heating conditions. The results showed that microbial loads in tested buckwheat kernels were in the range of 3.4-6.2 log CFU/g. Samples from Shanxi (SX-3) had significantly higher microbial counts than other samples. The selected four temperature-time combinations: 75 °C-20 min, 80 °C-10 min, 85 °C-5 min, and 90 °C-0 min of RF heating could reduce microbial counts to <3.0 log CFU/g in buckwheat kernels at 16.5% w.b. moisture content. Furthermore, the reduction populations of the inoculated pathogens (Salmonella Typhimurium, Escherichia coli, Cronobacter sakazakii, and Bacillus cereus) reached 4.0 log CFU/g under the above conditions, and almost 5.0 log CFU/g especially at high temperature-short holding time combinations (85 °C-5 min and 90 °C-0 min). Besides, physicochemical properties evaluation also showed the insignificant color changes and nutrients loss after RF treatment at 90 °C-0 min. Therefore, the RF heating at 90 °C-0 min holds greater potential than the other lower temperature-longer holding time combinations for applications in buckwheat pasteurization.

Inactivation of Salmonella enterica Serovar Typhimurium and Staphylococcus aureus in Rice by Radio Frequency Heating.

ABSTRACT: The objectives of this study were to determine the effect of the milling degree (MD) of rice (Oryza sativa L.) on the heating rate, pathogen inactivation (Salmonella Typhimurium and Staphylococcus aureus), and color change resulting from radio frequency (RF) heating. Rice samples inoculated with pathogens were placed in a polypropylene jar and subjected to RF heating for 0 to 75 s. The heating rate of rice with a 2% MD was the highest during RF heating, followed by those with a 0, 8, and 10% MD; the reduction of pathogens showed the same trend. The reductions of pathogen levels in rice with MDs of 0 and 2% were significantly higher than those observed for rice with MDs of 8 and 10% under the same treatment conditions. For example, log reductions of Salmonella Typhimurium in rice by 55-s RF heating were 3.64, 5.19, 2.18, and 1.80 for MDs of 0, 2, 8, and 10%, respectively. At the same treatment conditions, log reductions of S. aureus were 2.77, 5.08, 1.15, and 0.90 for MDs of 0, 2, 8, and 10%, respectively. The color of rice measured according to L*, a*, and b* was not significantly altered after RF heating, regardless of the MD. Therefore, the MD of rice should be considered before RF heating is applied to inactivate foodborne pathogens.

Multi-Channel RF Supervision Module for Thermal Magnetic Resonance Based Cancer Therapy.

Glioblastoma multiforme (GBM) is the most lethal and common brain tumor. Combining hyperthermia with chemotherapy and/or radiotherapy improves the survival of GBM patients. Thermal magnetic resonance (ThermalMR) is a hyperthermia variant that exploits radio frequency (RF)-induced heating to examine the role of temperature in biological systems and disease. The RF signals' power and phase need to be supervised to manage the formation of the energy focal point, accurate thermal dose control, and safety. Patient position during treatment also needs to be monitored to ensure the efficacy of the treatment and avoid damages to healthy tissue. This work reports on a multi-channel RF signal supervision module that is capable of monitoring and regulating RF signals and detecting patient motion. System characterization was performed for a broad range of frequencies. Monte-Carlo simulations were performed to examine the impact of power and phase errors on hyperthermia performance. The supervision module's utility was demonstrated in characterizing RF power amplifiers and being a key part of a feedback control loop regulating RF signals in heating experiments. Electromagnetic field simulations were conducted to calculate the impact of patient displacement during treatment. The supervision module was experimentally tested for detecting patient motion to a submillimeter level. To conclude, this work presents a cost-effective RF supervision module that is a key component for a hyperthermia hardware system and forms a technological basis for future ThermalMR applications.

Radio frequency heating improves water retention of pork myofibrillar protein gel: An analysis from water distribution and structure.

This study was to explore effects of hot air assisted or not assisted radio frequency (RF, 27.12 MHz, 1.4 kW) heating with different electrode gaps (100 mm, 120 mm, and 140 mm) on the water-holding capacity (WHC) of myofibrillar protein (MP) gel and to understand the underlying mechanism through chemical forces, water distribution, and structure. The results showed that the MP gels heated by RF (100 mm) had the highest WHC and uniform gel network structure. As for RF with 100 mm electrode gap, the increased ionic and hydrogen bonds might be conducive to the WHC compared to water bath heating, which was verified by Low-field nuclear magnetic resonance results that the free water converted into the immobilized water. Raman spectroscopy results revealed that RF (100 mm) induced the self-assembly of ß-sheet to α-helix, which conduced to the stable and ordered gel network structure.

Effects of radio frequency heating on water distribution and structural properties of grass carp myofibrillar protein gel.

This study explored effects of radio frequency (RF, 27.12 MHz, 3 kW) heating replacing the first stage (electrode gaps of 120, 140 and 160 mm) or/and the second stage (95 mm) of the water bath heating on water distribution and structural characteristics of grass carp myofibrillar proteins gels. Compared with control, RF heating (140) during the first stage significantly reduced the total time to prepare gels from 70 min to 45.3 min and increased springiness and water holding capacity from 62.9% to 68.3%. It may be attributed to the appropriate RF heating contributing to α-helix turning into random coil and cross-linking via hydrophobic interactions and disulfide bonds, thus forming smooth gels with clear network structures. Structural changes further affected water distribution (immobilized water increasing from 97.8% to 98.7%). Namely, RF (140 mm) heating improved water distribution and structural characteristics of gels, which provided basic information for RF heating surimi gels.

Radio frequency energy inactivates peroxidase in stem lettuce at different heating rates and associate changes in physiochemical properties and cell morphology.

Radio frequency (RF) is an emerging technology applied in blanching treatment as alternative to conventional treatment. This study aimed to investigate the effects of RF heating rate on peroxidase (POD) inactivating efficiency, physiochemical properties (texture, color and vitamin C) and cell structure of stem lettuce. POD enzyme inactivation efficiency increased with increased RF heating rate. When POD activity was reduced to <5%, better physiochemical properties and less cell damage occurred in RF heating compared with conventional hot water (HW) blanching (HWB); Relative electrolyte leakage (REL) analysis and microscopic observation suggested that the loss of integrity of cell walls and membranes, the decrease in turgor pressure and the weakened connections between adjacent cells leaded to the deterioration of physiochemical properties. The degrees of cell destruction varied with RF heating rates, which provide a new idea for RF blanching for producing different types of fruits and vegetables products (Solid and juice products).

Design, Implementation, Evaluation and Application of a 32-Channel Radio Frequency Signal Generator for Thermal Magnetic Resonance Based Anti-Cancer Treatment.

Thermal Magnetic Resonance (ThermalMR) leverages radio frequency (RF)-induced heating to examine the role of temperature in biological systems and disease. To advance RF heating with multi-channel RF antenna arrays and overcome the shortcomings of current RF signal sources, this work reports on a 32-channel modular signal generator (SGPLL). The SGPLL was designed around phase-locked loop (PLL) chips and a field-programmable gate array chip. To examine the system properties, switching/settling times, accuracy of RF power level and phase shifting were characterized. Electric field manipulation was successfully demonstrated in deionized water. RF heating was conducted in a phantom setup using self-grounded bow-tie RF antennae driven by the SGPLL. Commercial signal generators limited to a lower number of RF channels were used for comparison. RF heating was evaluated with numerical temperature simulations and experimentally validated with MR thermometry. Numerical temperature simulations and heating experiments controlled by the SGPLL revealed the same RF interference patterns. Upon RF heating similar temperature changes across the phantom were observed for the SGPLL and for the commercial devices. To conclude, this work presents the first 32-channel modular signal source for RF heating. The large number of coherent RF channels, wide frequency range and accurate phase shift provided by the SGPLL form a technological basis for ThermalMR controlled hyperthermia anti-cancer treatment.

Inactivation of Escherichia coli, Salmonella enterica serovar Typhimurium, and Bacillus cereus in roasted grain powder by radio frequency heating.

AIMS: The objective of this study was to evaluate the antimicrobial effects of radio frequency (RF) heating and the combination treatment of RF heating with ultraviolet (UV) radiation against foodborne pathogens in roasted grain powder (RGP). METHODS AND RESULTS: Foodborne pathogens inoculated on RGP were subjected to RF heating or RF-UV combination treatments. After 120 s of RF heating, 4·68, 3·89 and 4·54 log reductions were observed for Escherichia coli, Salmonella Typhimurium and Bacillus cereus vegetative cells respectively. The combined RF-UV treatment showed synergistic effects of over 1 log unit compared to the sum of individual treatment for E. coli and S. Typhimurium, but not for B. cereus vegetative cells because of their high UV resistance. Germinated B. cereus cells were not significantly inactivated by RF heating (<1 log CFU per gram), and increased heat resistance compared to the vegetative cells was verified with mild heat treatment. The colour of RGP was not significantly affected by the RF or RF-UV treatments. CONCLUSIONS: Applying RF heating to grain-based food products has advantages for the inactivation of E. coli and S. Typhimurium in RGP. SIGNIFICANCE AND IMPACT OF THE STUDY: The results of the present study could be used as a basis for determining the treatment conditions for inactivating E. coli and other foodborne pathogens such as S. Typhimurium and B. cereus in RGP.

Controlled Release of Therapeutics from Thermoresponsive Nanogels: A Thermal Magnetic Resonance Feasibility Study.

Thermal magnetic resonance (ThermalMR) accommodates radio frequency (RF)-induced temperature modulation, thermometry, anatomic and functional imaging, and (nano)molecular probing in an integrated RF applicator. This study examines the feasibility of ThermalMR for the controlled release of a model therapeutics from thermoresponsive nanogels using a 7.0-tesla whole-body MR scanner en route to local drug-delivery-based anticancer treatments. The capacity of ThermalMR is demonstrated in a model system involving the release of fluorescein-labeled bovine serum albumin (BSA-FITC, a model therapeutic) from nanometer-scale polymeric networks. These networks contain thermoresponsive polymers that bestow environmental responsiveness to physiologically relevant changes in temperature. The release profile obtained for the reference data derived from a water bath setup used for temperature stimulation is in accordance with the release kinetics deduced from the ThermalMR setup. In conclusion, ThermalMR adds a thermal intervention dimension to an MRI device and provides an ideal testbed for the study of the temperature-induced release of drugs, magnetic resonance (MR) probes, and other agents from thermoresponsive carriers. Integrating diagnostic imaging, temperature intervention, and temperature response control, ThermalMR is conceptually appealing for the study of the role of temperature in biology and disease and for the pursuit of personalized therapeutic drug delivery approaches for better patient care.

Effect of radio frequency treatment on functional, structural and thermal behaviors of protein isolates in rice bran.

To investigate the influence of radio frequency (RF) stabilization treatment on rice bran protein isolate (RBPI) properties, functional, structural and thermal behaviors of RBPI obtained from RF treated RB were evaluated under various temperatures between 80 and 120 °C holding for 5 min. The results showed that RF heating had negative impact on the yield, purity, foaming properties and solubility of RBPI when the treatment temperature was higher than 100 °C, while the absorption and emulsifying properties were improved. No significant changes were observed in primary structure of RF treated samples, but the second structure changed with an increase in random coil and a decrease in ß-sheet, α-helix and ß-turn. The decreased tryptophan fluorescence and increased surface hydrophobicity suggested alterations in tertiary structure. RF treatment also caused noticeable decrease in denaturation temperature and enthalpy of RBPI. The results would provide basic information for food applications of proteins isolated from RF stabilized RB.

The effect of radio-frequency heating on vacuum-packed saury (Cololabis saira) in water.

We characterized vacuum-packed whole saury (Cololabis saira) treated using radio-frequency (RF) heating and compared it with that treated using conventional retort heating. RF heating is electrical heating based on dielectric heating. In this study, the effect of RF heating on softening and collagen in backbone was analyzed. RF heating heated the center of fish faster than water. The backbone was softened to a chewable level, and the heating time was shortened to one-third. The amount of crude protein and collagen in backbone decreased with decreasing elasticity, although that heated using RF (131°C) still contained a higher amount than conventional heating. However, ß and γ collagen, and then α1 and α2 collagen chain in backbone disappeared with heating; therefore, collagen was degraded to collagen peptide. Results confirmed that RF heating provided wholly eatable fish containing low-molecular collagen peptide in a short heating time.

Magnetic resonance conditional paramagnetic choke for suppression of imaging artifacts during magnetic resonance imaging.

Higher risk patient populations require continuous physiological monitoring and, in some cases, connected life-support systems, during magnetic resonance imaging examinations. While recently there has been a shift toward wireless technology, some of the magnetic resonance imaging devices are still connected to the outside using cabling that could interfere with the magnetic resonance imaging's radio frequency during scanning, resulting in excessive heating. We developed a passive method for radio frequency suppression on cabling that may assist in making some of these devices magnetic resonance imaging compatible. A barrel-shaped strongly paramagnetic choke was developed to suppress induced radio frequency signals which are overlaid onto physiological monitoring leads during magnetic resonance imaging. It utilized a choke placed along the signal lines, with a gadolinium solution core. The choke's magnetic susceptibility was modeled, for a given geometric design, at increasing chelate concentration levels, and measured using a vibrating sample magnetometer. Radio frequency noise suppression versus frequency was quantified with network-analyzer measurements and tested using cabling placed in the magnetic resonance imaging scanner. Temperature-elevation and image-quality reduction due to the device were measured using American Society for Testing and Materials phantoms. Prototype chokes with gadolinium solution cores exhibited increasing magnetic susceptibility, and insertion loss (S21) also showed higher attenuation as gadolinium concentration increased. Image artifacts extending <4 mm from the choke were observed during magnetic resonance imaging, which agreed well with the predicted ∼3 mm artifact from the electrochemical machining simulation. An accompanying temperature increase of <1 °C was observed in the magnetic resonance imaging phantom trial. An effective paramagnetic choke for radio frequency suppression during magnetic resonance imaging was developed and its performance demonstrated.

Effects of radio frequency assisted blanching on polyphenol oxidase, weight loss, texture, color and microstructure of potato.

This paper is focused on the effects of radio frequency (RF) heating on the relative activity of polyphenol oxidase (PPO), weight loss, texture, color, and microstructure of potatoes. The results showed that pure mushroom PPO was almost completely inactivated at 80 °C by RF heating. The relative activity of potato PPO reduced to less than 10% with increasing temperature (25-85 °C). Enzyme extract showed the lowest PPO relative activity at 85 °C after RF treatment, followed by the potato cuboids and mashed potato, about 0.19 ±â€¯0.017%, 3.24 ±â€¯0.19%, and 3.54 ±â€¯0.04%, respectively. Circular dichroism analysis indicated that RF heating changed the secondary structure of PPO, as α-helix content decreased. Both electrode gap and temperature had significant effect (P < .05) on weight loss, color, and texture of the potato cuboids. Microstructure analysis showed the changes of potato cell and starch during RF heating.