Field Applicator Research Articles

Light-Controlled Magnetic Properties: An Energy-Efficient Opto-Mechanical Control over Magnetic Films by Liquid Crystalline Networks.

Magnetostrictive materials are essential components in sensors, actuators, and energy-storage devices due to their ability to convert mechanical stress into changes in magnetic properties and vice-versa. However, their operation typically requires physical contact to apply stress or relies on magnetic field sources to control magnetic properties. This poses significant limitations to devices miniaturization and their integration into contactless technologies. This work reports on an approach that overcomes these limitations by using light to transfer mechanical stress to a magnetostrictive device, thereby achieving non-contact and reversible opto-mechanical control of its magnetic and electrical properties. The proposed solution combines a magnetostrictive Fe70Ga30 thin film with a photo-responsive Liquid Crystalline Network (LCN). Magnetic properties are modulated by changing the light wavelength and illumination time. Remarkably, the stable shape change of the LCN induced by ultraviolet (UV) light leads to the retention of magnetic properties even after the light is switched off, resulting in a magnetic memory effect with an energy consumption advantage over the use of conventional magnetic field applicators. The memory effect is erased by visible light, which releases the mechanical stress in the photoresponsive layer. Therefore, this new composite material creates a fully reconfigurable magnetic system controlled by light.

Personalized Intraoperative Radiotherapy Balloon Applicator Design and Production With 3D Printer

Radiation is the energy released from matter. Radiation is divided into two according to its source: natural and artificial radiation. Artificial radiation is used in treatment methods in medicine. One of these treatment methods is brachytherapy. Brachytherapy treatment is applied by placing small radioactive sources inside the body and sending beams directly to the cancerous cell. The main thing to consider in brachytherapy treatment is the selection of the applicator. The applicator is the device that enters the patient's body cavity. 
 In this study, based on the applicators currently used in the medical field, a patient-specific, biocompatible, sterilized, and reusable applicator will be created from PLA material by using a 3D printer.
 The applicator to be designed will consist of 2 parts: the intrauterine tube and the spherical tip. The spherical tips, which vary according to the size of the tumor, will be pressed to integrate with the tube part of the applicator. Thus, a patient-specific design will be realized by using the spherical tip suitable for the patient’s tumor region.
 As a result of the project, since the applicator will have spherical tips of different sizes, it completely covers the intrabody cavity of the patient. Thus, the movement of the applicator is limited, and dose distribution is prevented. The treatment process of the patient is improved.
 Another result is that the prototype applicator printed with PLA filament is produced at a very low cost. Thus, access to the applicator becomes easier and its use in the medical field increases.

Design and Validation of Experimental Setup for Cell Spheroid Radiofrequency-Induced Heating.

While hyperthermia has been shown to induce a variety of cytotoxic and sensitizing effects on cancer tissues, the thermal dose-effect relationship is still not well quantified, and it is still unclear how it can be optimally combined with other treatment modalities. Additionally, it is speculated that different methods of applying hyperthermia, such as water bath heating or electromagnetic energy, may have an effect on the resulting biological mechanisms involved in cell death or in sensitizing tumor cells to other oncological treatments. In order to further quantify and characterize hyperthermia treatments on a cellular level, in vitro experiments shifted towards the use of 3D cell spheroids. These are in fact considered a more representative model of the cell environment when compared to 2D cell cultures. In order to perform radiofrequency (RF)-induced heating in vitro, we have recently developed a dedicated electromagnetic field applicator. In this study, using this applicator, we designed and validated an experimental setup which can heat 3D cell spheroids in a conical polypropylene vial, thus providing a reliable instrument for investigating hyperthermia effects at the cellular scale.

Development of handheld induction heaters for magnetic fluid hyperthermia applications and in-vitro evaluation on ovarian and prostate cancer cell lines

Objective: Magnetic fluid hyperthermia (MFH) is a still experimental technique found to have a potential application in the treatment of cancer. The method aims to reach around 41 °C–47 °C in the tumor site by exciting magnetic nanoparticles with an externally applied alternating magnetic field (AMF), where cell death is expected to occur. Applying AMFs with high spatial resolution is still a challenge. The AMFs from current and prospective MFH applicators cover relatively large areas; being not suitable for patients having metallic implants near the treatment area. Thus, there will be a clinical need for smaller magnetic field applicators. To this end, a laparoscopic induction heater (LIH) and a transrectal induction heater (TRIH) were developed. Methods: Miniature ‘pancake’ coils were wound and inserted into 3D printed enclosures. Ovarian (SKOV-3, A2780) and prostate (PC-3, LNCaP) cancer cell lines were used to evaluate the instruments’ capabilities in killing cancer cells in vitro, using Synomag®-D nanoparticles as the heat mediators. NIH3T3 normal cell lines were also used with both devices to observe if these cells tolerated the conditions applied. Results: Magnetic field intensities reached by the LIH and TRIH were 42.6 kA m−1 at 326 kHz and 26.3 kA m−1 at 303 kHz, respectively. Temperatures reached in the samples were 41 °C by the LIH and 43 °C by the TRIH. Both instruments successfully accomplished killing cancer cells, with minimal effects on normal cells. Conclusion: This work presents the first line of handheld medical induction heaters and have the potential to be a complement to existing cancer therapies. Significance: These instruments could enable the development of MFH modalities that will facilitate the clinical translation of this thermal treatment.

Validation of a Temperature-Feedback Controlled Automated Magnetic Hyperthermia Therapy Device.

We present in vivo validation of an automated magnetic hyperthermia therapy (MHT) device that uses real-time temperature input measured at the target to control tissue heating. MHT is a thermal therapy that uses heat generated by magnetic materials exposed to an alternating magnetic field. For temperature monitoring, we integrated a commercial fiber optic temperature probe containing four gallium arsenide (GaAs) temperature sensors. The controller device used temperature from the sensors as input to manage power to the magnetic field applicator. We developed a robust, multi-objective, proportional-integral-derivative (PID) algorithm to control the target thermal dose by modulating power delivered to the magnetic field applicator. The magnetic field applicator was a 20 cm diameter Maxwell-type induction coil powered by a 120 kW induction heating power supply operating at 160 kHz. Finite element (FE) simulations were performed to determine values of the PID gain factors prior to verification and validation trials. Ex vivo verification and validation were conducted in gel phantoms and sectioned bovine liver, respectively. In vivo validation of the controller was achieved in a canine research subject following infusion of magnetic nanoparticles (MNPs) into the brain. In all cases, performance matched controller design criteria, while also achieving a thermal dose measured as cumulative equivalent minutes at 43 °C (CEM43) 60 ± 5 min within 30 min.

Characterization and Dosimetry of 15-MeV Electron Beam from Elekta Synergy Platform Linear Accelerator Using Square Field Applicators

Characterization and Dosimetry of 15-MeV Electron Beam from Elekta Synergy Platform Linear Accelerator Using Square Field Applicators

In silico experiments as a tool to reduce preclinical tests of magnetic hyperthermia

In silico models can be useful tools to guide preclinical tests of magnetic hyperthermia, which employs Magnetic Nanoparticles (MNPs) excited by AC magnetic fields, as heat mediators for cancer cure. We virtually reproduce the heating process induced by magnetic hyperthermia in murine models, as a function of field applicator features, properties and size of target tissue, MNP dose and animal size.

In silico experiments as a tool to reduce preclinical tests of magnetic hyperthermia

In silico models can be useful tools to guide preclinical tests of magnetic hyperthermia, which employs Magnetic Nanoparticles (MNPs) excited by AC magnetic fields, as heat mediators for cancer cure. We virtually reproduce the heating process induced by magnetic hyperthermia in murine models, as a function of field applicator features, properties and size of target tissue, MNP dose and animal size.

In vitro hyperthermic effect of magnetic fluid on cervical and breast cancer cells

Self-regulating temperature-controlled nanoparticles such as Mn–Zn ferrite nanoparticles based magnetic fluid can be a better choice for magnetic fluid hyperthermia because of its controlled regulation of hyperthermia temperature window of 43–45 °C. To test this hypothesis magnetic fluid with said properties was synthesized, and its effect on cervical and breast cancer cell death was studied. We found that the hyperthermia window of 43–45 °C was maintained for one hour at the smallest possible concentration of 0.35 mg/mL without altering the magnetic field applicator parameters. Their hyperthermic effect on HeLa and MCF7 was investigated at the magnetic field of 15.3 kA/m and frequency 330 kHz, which is close to the upper safety limit of 5 * 109 A/m s. We have tested the cytotoxicity of synthesized Mn–Zn ferrite fluid using MTT assay and the results were validated by trypan blue dye exclusion assay that provides the naked eye microscopic view of actual cell death. Since cancer cells tend to resist treatment and show re-growth, we also looked into the effect of multiple sessions hyperthermia using a 24 h window till 72 h using trypan blue assay. The multiple sessions of hyperthermia showed promising results, and it indicated that a minimum of 3 sessions, each of one-hour duration, is required for the complete killing of cancer cells. Moreover, to simulate an in vivo cellular environment, a phantom consisting of magnetic nanoparticles dispersed in 1 and 5% agarose gel was constituted and studied. These results will help to decide the magnetic fluid based hyperthermic therapeutic strategies using temperature-sensitive magnetic fluid.

Radiation Losses From a Microwave Surface-Wave Sustained Plasma Source (Surfatron)

Surfatron is an electromagnetic (EM) field applicator yielding surface-wave (SW) discharges (SWDs) within dielectric tubes in a broad range of operating conditions. In this article, the vector wave equation for the electric field is solved numerically in 2-D to determine the influence of plasma parameters, such as electron density, normalized electron–neutral collisions frequency, plasma column length and radius, as well as the length of the surfatron body on the field strength distribution, radiation patterns, and ratio of radiated power to power absorbed in plasma. This analysis allows for estimating the efficiency of plasma generation. The model takes into account the surfatron configuration, reproducing the typical SWD plasma column behavior, namely the fact that the plasma column is “pushed out” of the surfatron interstice as absorbed power increases. The surfatron is assumed to be placed in an air-filled sphere with the surface transparent to the wave. Calculations are performed for a field frequency of 2450 MHz and a fused silica tube, considering plasma parameters typical for both atmospheric- and lower-pressure discharge gases for achieving a parametric survey. It is found that for given plasma parameters, varying the plasma column length from a few up to 30 cm significantly affects the distribution of the electric field around the surfatron and the radiation patterns. It is further shown that the radiated to absorbed power ratio increases with increasing electron density and plasma radius, and decreasing electron–neutral collision frequency. This ratio can exceed 30% for a 30-cm plasma column with a plasma radius of 3 mm and parameters typical for atmospheric and reduced gas pressures. The surfatron length at which radiation losses are minimal is at half the vacuum wavelength.

Preliminary in-vitro investigation of magnetic fluid hyperthermia in cervical cancer cells

The present study reports auto-tunable temperature sensitive iron-based magnetic nanoparticles fluid synthesized for its application in magnetic fluid hyperthermia. The effect of magnetic field and concentration of the sample is investigated for the induction heating at 350 kHz frequency. The concentration of magnetic fluid and magnetic field was optimized based on the specific absorption of the sample. The cytotoxicity of the optimized magnetic fluid was analyzed on cervical cancer cell line HeLa with and without magnetic field applicator by performing MTT assay. The cytotoxicity assay after induction heating for the magnetic fluid showed cell death up to 75% for 24 h of interaction of fluid with cells. Upon increasing the time of interaction of magnetic fluid to 36 h and for 60 min hyperthermia heating session, almost all cells were found dead. The preliminary analysis revealed significant efficacy of the synthesized magnetic fluid to caused cell death due to hyperthermia of one hour session. In future such type of magnetic fluids can be used for localized treatment of cancer under magnetic field.

Improvement of palladium limit of detection by microwave-assisted laser induced breakdown spectroscopy

Detecting elements such as heavy metals is important in many industrial processes. The techniques currently used are time consuming and require excessive sample preparation. In this paper, we demonstrate microwave-assisted laser-induced breakdown spectroscopy (MW-LIBS) to detect palladium (Pd) in solid samples at ambient conditions. Microwave radiation was introduced by a near field applicator to couple the microwave radiation with the plasma. The results were a 92–fold enhancement in palladium signal with 8-fold improvement in the limit of detection at laser energy levels below 5 mJ (1250 J/cm2 laser pulse fluence). We also investigate the optimum experimental parameters of palladium detection for both laser-induced breakdown spectroscopy (LIBS) and MW-LIBS. The maximum signal to noise ratio improvement was achieved at microwave power of 750 W and laser pulse fluence of 157 J/cm2 for Pd I 340.46 nm. Finally, we examine the location of the near field applicator (NFA) with respect to the sample to show that the MW-LIBS signal strength was significantly affected by the vertical position compared to the horizontal. The detection limits of palladium with LIBS and MW-LIBS were 40 ppm and 5 ppm respectively.

Low-temperature helium plasma generated at atmospheric pressures by non-standard field applicator

Low-temperature helium plasmas were sustained using radio frequency excitation waveforms in a cylindrical glass tube, both in steady state and flowing conditions.

Radio Frequency Heating of Carbon Nanotube Composite Materials.

Here, we give the first-ever report of radio frequency (RF) electromagnetic heating of polymer nanocomposite materials via direct-contact and capacitively coupled electric field applicators. Notably, RF heating allows nanocomposite materials to be resistively heated with electric fields. We highlight our novel RF heating technique for multiwalled carbon nanotube (MWCNT) thermoplastic composites and measure their broadband dielectric properties. We also demonstrate three different electric field applicator configurations and discuss their practical use in an industrial setting. We demonstrate the use of RF heating to cure an automotive-grade epoxy loaded with MWCNTs. Our results show that lap shear joints cured faster with the RF method compared with control samples cured in an oven because of the heat-transfer advantages of directly heating the epoxy composite. Finally, we implement our RF curing technique to assemble an automotive structure by locally curing an epoxy adhesive applied to a truck chassis.

Remote magnetic actuation using a clinical scale system.

Remote magnetic manipulation is a powerful technique for controlling devices inside the human body. It enables actuation and locomotion of tethered and untethered objects without the need for a local power supply. In clinical applications, it is used for active steering of catheters in medical interventions such as cardiac ablation for arrhythmia treatment and for steering of camera pills in the gastro-intestinal tract for diagnostic video acquisition. For these applications, specialized clinical-scale field applicators have been developed, which are rather limited in terms of field strength and flexibility of field application. For a general-purpose field applicator, flexible field generation is required at high field strengths as well as high field gradients to enable the generation of both torques and forces on magnetic devices. To date, this requirement has only been met by small-scale experimental systems. We have built a highly versatile clinical-scale field applicator that enables the generation of strong magnetic fields as well as strong field gradients over a large workspace. We demonstrate the capabilities of this coil-based system by remote steering of magnetic drills through gel and tissue samples with high torques on well-defined curved trajectories. We also give initial proof that, when equipped with high frequency transmit-receive coils, the machine is capable of real-time magnetic particle imaging while retaining a clinical-scale bore size. Our findings open the door for image-guided radiation-free remote magnetic control of devices at the clinical scale, which may be useful in minimally invasive diagnostic and therapeutic medical interventions.

Microwave assisted laser-induced breakdown spectroscopy at ambient conditions

Signal enhancements in laser-induced breakdown spectroscopy (LIBS) using external microwave power are demonstrated in ambient air. Pulsed microwave at 2.45GHz and of 1millisecond duration was delivered via a simple near field applicator (NFA), with which an external electric field is generated and coupled into laser induced plasma. The external microwave power can significantly increase the signal lifetime from a few microseconds to hundreds of microseconds, resulting in a great enhancement on LIBS signals with the use of a long integration time. The dependence of signal enhancement on laser energy and microwave power is experimentally assessed. With the assistance of microwave source, a significant enhancement of ~100 was achieved at relatively low laser energy that is only slightly above the ablation threshold. A limit of detection (LOD) of 8.1ppm was estimated for copper detection in Cu/Al2O3 solid samples. This LOD corresponds to a 93-fold improvement compared with conventional single-pulse LIBS. Additionally, in the microwave assisted LIBS, the self-reversal effect was greatly reduced, which is beneficial in measuring elements of high concentration. Temporal measurements have been performed and the results revealed the evolution of the emission process in microwave-enhanced LIBS. The optimal position of the NFA related to the ablation point has also been investigated.

Liver damage associated with exposure to aspirin and diazinon in male rats and the ameliorative effect of selenium

PurposeThe widespread use of organophosphorus insecticides (OPIs) consequently leads to the exposure of manufacturing workers, field applicators, the ecosystem, and finally the public to the possible toxic effects of OPIs. In addition, drugs or pharmaceutical products, which are used to cure diseases, are also xenobiotics with both therapeutic/toxic potentials. It is evident from the literature, which is very limited, that drug/insecticide interactions can result in altered response/toxicity, which is of clinical relevance. The aim of the present study was designed to assess the adverse effects of exposure to aspirin and diazinon and their combination on liver of male rats and hepatoprotective potential of selenium (Se). MethodsRats were oral administered with vehicle, acetyl salicylic acid (ASA) at the maximum administration dose (1350mg/personal/day=22.5mg/kg. b.wt.), diazinon (DIA) at 20mg/kg. b.wt. and Se at a dose of 200μg/kg b.wt./day and their combinations for 28 consecutive days. Serum liver biomarkers, e.g. ALT&AST, ALP, ChE, LDH, albumin, total protein were determined as well as histological and histochemical studies. ResultsBody weight was statistically (P≤0.05) decreased, while relative liver weight was statistically (P≤0.05) increased in DIA and ASA+DIA-treated groups. The activities of serum aspartate aminotransferase (AST), alanine transaminase (ALT), alkaline phosphatase (ALP) and lactate dehydrogenase (LDH) were statistically (P≤0.05) increased, while the activity of cholinesterase (ChE) was decreased in rats exposed to DIA, ASA and DIA+ASA. In addition, administration of DIA, ASA and their combination resulted in damage of liver structures and increase in the immunoreactivity of caspase-3 expression in the cytoplasm of the hepatocytes as compared to the control group. Combination therapy with Se significantly (P≤0.05) restored these alterations to within the normal limits and prevents disruptions of liver structures. ConclusionsThe present study indicates that liver enzymes, histopathology and immunoreactivity of caspase-3 would trigger ASA- and DIA-induced liver injury. The severities of such observations were more pronounced in their combined exposure. Combination therapy with Se restored these alterations to within the normal limits and prevents disruptions of liver structures. The data throw light on the problem of simultaneous exposure to OPIs and commonly used drugs especially that are metabolised by CYP450. Accordingly, ASA should be avoided since many of the adverse effects associated with these drugs are similar to the complications of chronic liver disease especially of agricultural workers in developing countries, where the handling of drugs without medical prescription. We suppose that antioxidant supplementation may be beneficial for the people using ASA for longer periods.

Hepato-renal damage and oxidative stress associated with pirimiphos-methyl exposure in male mice

Objective: For many years, the organophosphorus insecticide pirimiphos-methyl (PM) was used as a valuable tool against several stored-product insect species. However, the knowledge of its toxicity for field applicators, manufacturing workers and public health is very limited in literatures. The present work was therefore undertaken in order to investigate the hepato-renal toxicity associated with PM exposure in mice. Method: Mice were divided into five groups of six mice each and administered PM at doses of 0.03 (ADI), 10 (NOAEL), 31.05 ( 1 /40 LD50) and 62.11 ( 1 /20 LD50) mg/kg body weight in corn oil for 45 days via oral gavage. Result: The results revealed that the activities of serum enzymes alkaline phosphatase, alanine and aspartate aminotransferases, and serum levels of total protein, urea and creatinine were significantly elevated (by 13-63% of control activity), whereas the level of serum albumin was significantly reduced (by 15-21%) following administration of 31.05 and 62.11 mg pirimiphosmethyl/kg body weight. In liver and kidney tissues, level of glutathione and the activity of superoxide dismutase and catalase enzymes were significantly decreased, while the level of lipid peroxidation were significantly increased compared to the control group. The lower doses of (ADI, NOAEL) PM induced insignificant or limited alteration in the above-mentioned biochemical parameters. Histopathological examination revealed hepato-renal cellular damage in all tested doses of PM compared to untreated group. Conclusion: The intensity of the insults in liver and kidney functions as well as oxidative damage represented by biochemical alterations and histopathological findings were demonstrated in a dose-dependent manner. © 2014 GESDAV

Magnetic fluid hyperthermia for bladder cancer: A preclinical dosimetry study

Purpose: This paper describes a preclinical investigation of the feasibility of thermotherapy treatment of bladder cancer with magnetic fluid hyperthermia (MFH), performed by analysing the thermal dosimetry of nanoparticle heating in a rat bladder model. Materials and methods: The bladders of 25 female rats were instilled with magnetite-based nanoparticles, and hyperthermia was induced using a novel small animal magnetic field applicator (Actium Biosystems, Boulder, CO). We aimed to increase the bladder lumen temperature to 42 °C in <10 min and maintain that temperature for 60 min. Temperatures were measured within the bladder lumen and throughout the rat with seven fibre-optic probes (OpSens Technologies, Quebec, Canada). An MRI analysis was used to confirm the effectiveness of the catheterisation method to deliver and maintain various nanoparticle volumes within the bladder. Thermal dosimetry measurements recorded the temperature rise of rat tissues for a variety of nanoparticle exposure conditions. Results: Thermal dosimetry data demonstrated our ability to raise and control the temperature of rat bladder lumen ≥1 °C/min to a steady state of 42 °C with minimal heating of surrounding normal tissues. MRI scans confirmed the homogenous nanoparticle distribution throughout the bladder. Conclusion: These data demonstrate that our MFH system with magnetite-based nanoparticles provides well-localised heating of rat bladder lumen with effective control of temperature in the bladder and minimal heating of surrounding tissues.

Exploration of rectangular waveguides as a basis for microwave enhanced continuous flow chemistries

In the context of microwave enhanced chemistry, usually a narrow set of single and multimode cavities are considered as microwave field applicators. This study aims to widen this current scope by exploring the potential of rectangular waveguides as a basis for microwave applicator systems. It is demonstrated that such systems offer microwave field patterns that are relatively simple and predictable, which makes processing amenable for adaption to specific requirements and for optimization. The feasibility of long residence time continuous flow chemistries under microwave conditions is demonstrated in a novel reactor type that the rectangular waveguide uniquely supports.