Radiofrequency Generator Research Articles

Development of a Three-Dimensional Multi-Modal Perfusion-Thermal Electrode System for Complete Tumor Eradication.

Simple SummaryImage-guided thermal-ablation techniques, such as radiofrequency ablation (RFA), have become the principal tools for treatment of unresectable primary and secondary tumors. However, tumor recurrences post-thermal ablation of medium to large-sized tumors frequently occur due to incomplete ablation of tumor margins. In the present study, we aim to specifically conquer this clinical problem through revolutionizing current thermal ablation technology by development of an innovative three-dimensional, multi-modal, perfusion-thermal electrode system, with the evidence of potential to simultaneously deliver therapeutics and RFA-medicated peritumoral hyperthermia into the difficult-to-treat tumor margins, to further eradicate the residual tumor cells during the thermal ablation.Background: Residual viable tumor cells after ablation at the tumor periphery serve as the source for tumor recurrence, leading to treatment failure. Purpose: To develop a novel three-dimensional (3D) multi-modal perfusion-thermal electrode system completely eradicating medium-to-large malignancies. Materials and Methods: This study included five steps: (i) design of the new system; (ii) production of the new system; (iii) ex vivo evaluation of its perfusion-thermal functions; (iv) mathematic modeling and computer simulation to confirm the optimal temperature profiles during the thermal ablation process, and; (v) in vivo technical validation using five living rabbits with orthotopic liver tumors. Results: In ex vivo experiments, gross pathology and optical imaging demonstrated the successful spherical distribution/deposition of motexafin gadolinium administered through the new electrode, with a temperature gradient from the electrode core at 80 °C to its periphery at 42 °C. An excellent repeatable correlation of temperature profiles at varying spots, from the center to periphery of the liver tumor, was found between the mathematic simulation and actual animal tumor models (Pearson coefficient ≥0.977). For in vivo validation, indocyanine green (ICG) was directly delivered into the peritumoral zones during simultaneous generation of central tumoral lethal radiofrequency (RF) heat (>60 °C) and peritumoral sublethal RF hyperthermia (<60 °C). Both optical imaging and fluorescent microscopy confirmed successful peritumoral ICG distribution/deposition with increased heat shock protein 70 expression. Conclusion: This new 3D, perfusion-thermal electrode system provided the evidence on the potential to enable simultaneous delivery of therapeutic agents and RF hyperthermia into the difficult-to-treat peritumoral zones, creating a new strategy to address the critical limitation, i.e., the high incidence of residual and recurrent tumor following thermal ablation of unresectable medium-to-large and irregular tumors.

A radio-frequency generator for ion thrusters based on a Class-E power circuit

Operating a radio-frequency ion thruster (RIT) requires a high frequency current flowing through an induction coil in order to ignite and maintain an inductively coupled plasma discharge (ICP). Several methods to create that current have been demonstrated and evaluated regarding complexity, flexibility and efficiency. Especially in space applications reliability and minimal power loss is crucial to comply to strict mission requirements. As one of the leanest concepts in terms of required components and nevertheless highest possible efficiency, the Class-E power circuit has proven itself as a well suited radio-frequency generator (RFG) of a RIT system. However, electrical performance and especially electromagnetic compatibility (EMC) during operation have not been evaluated, but are essential if the system is intended for use in space. In order to fill this gap and bring the Class-E circuit into the fold of established RFG concepts, a prototype was designed, built, and used to operate a RIT-10. For reference, a conventional Half-Bridge RFG was tested under the same operating conditions. Further investigations are concerned with EMC behaviour of both devices and show that Class-E circuit exhibits significantly lower electromagnetic emission during operation compared to the Half-Bridge reference.

Low-Phase-Noise Tenfold Frequency Multiplication Based on Integrated Optical Frequency Combs

We experimentally demonstrate a low-phase-noise tenfold frequency multiplier based on a compact integrated optical frequency comb (OFC) generator. The Indium Phosphide (InP) monolithically integrated OFC is based on a flexible scheme using cascaded optical modulators. The extremely compact frequency multiplier is broadly tunable in wavelength and in OFC repetition frequency, making it interesting for high-spectral-purity mm-waves applications. OFC generation with a 2.6 GHz spacing and 19 tones within a 10 dB power range and an optical signal-to-noise ratio (OSNR) higher than 40 dB is reported. Using a 74 GHz-bandwidth photodetector, we achieve a set of 2.6 GHz phase-stabilized electrical tones, reaching carriers up to 39 GHz with a high signal-to-noise ratio (SNR). In particular, the OFC-based tenfold-multiplied signal (26 GHz) provides a remarkable low-phase-noise feature, equivalent to the commercially available radiofrequency (RF) generator used as a source at the same electrical power. At 26 GHz, phase-noise of −50 dBc/Hz and −80 dBc/Hz are reported for 10 Hz and 1 kHz offsets, respectively. The proposed system enables frequency multiplication up to 12-times without phase impairments, i.e., phase noise performance equivalent to a commercial RF generator, validating its potential to low-phase-noise and high-spectral-purity mm-wave applications.

Optical phase-locked loop phase noise in 5G mm-wave OFDM ARoF systems

The use of millimeter-wave (mm-wave) frequencies is required in order to support the increasing number of connected devices expected from the fifth generation (5G) of mobile communications. Subsequently, the generation of radio-frequency (RF) carriers ranging from 10GHz to 300GHz and their transport through optical distribution network (ODN) is a key element of the future 5G fronthaul. Optically assisted RF carrier generation is one of the most promising solutions to tackle this issue, allowing a wide use of analog radio-over-fiber (ARoF) architectures. However the main limitation of these optical methods is related to the finite coherence of lasers sources, which can dramatically degrade data transmission in analog formats. To mitigate its impact, the use of orthogonal frequency-division multiplexing (OFDM) as the 5G standard allows employing efficient phase noise compensation algorithms. Therefore, in this study, we present an experimental demonstration of a mm-wave generation technique based on an optical phase-locked loop (OPLL) that fulfills the frequency specifications for 5G. Then, an algorithm is introduced that improves data recovery at reception and reduces the impact of a possible high phase noise carrier. Finally, a back-to-back data transmission experiment is performed, demonstrating the efficiency of the algorithm to reach the 5G requirements. These results emphasize the use of OPLLs as a viable solution to generate mm-wave carriers for 5G and beyond.

Extending thermal stability of short-living soliton states in silicon nitride microring resonators

Dissipative Kerr solitons in microresonators enable on-chip chip generation of low-noise optical pulse trains with high repetition rates, finding applications in optical communication, distance measurement, spectroscopy and radiofrequency generation. However, the most common photonic integrated platforms often show very short living, hence difficult to achieve, soliton states. Here, we exploit an auxiliary resonance to access soliton regime in Si3N4 microresonators by simple wavelength scanning. We increase the likelihood of single soliton formation by more than two times using backward tuning of the laser, and we show that the increased thermal stability allows soliton formation by thermal tuning of the whole sample, keeping the laser at a fixed frequency.

Atmospheric pressure plasma jet: formation of Wenzel’s model supportive surface modification on PMMA

ABSTRACT The generation of cold plasma at atmospheric pressure by using atmospheric-pressure plasma jet (APPJ) system and its use in the treatment of the poly-methyl-methacrylate (PMMA) have been reported in the manuscript. The cold plasma is generated at atmospheric pressure with 120 watt and 200 watt power and 3 litres/min and 5 litres/min argon flow using a 13.56 MHz radio frequency generator. PMMA samples are treated with aforesaid parameters for different time durations. After treatment, the formation of a carbon-rich surface has been observed, while a visible and significant amount of changes in surface morphology, roughness, adhesion strength and contact angle have been observed. Due to the APPJ treatment, the Wenzel’s model supportive microconical structures have been formed for hydrophobic surfaces. Optical emission spectroscopy has been used to identify the various species in the plasma and for electron temperature measurement. The discharge phenomenon at atmospheric pressure has been understood using the basic plasma model. The interaction of the plasma with the surface has been explained using the sub-plantation model.

Evaluation of disorders of adaptive mechanisms in heart failure by microwave dielectrometry

Differential diagnosis of stress adaptive mechanisms is one of the areas of modern biomedical engineering and the most complex part of the pre-nosological diagnosis of cardiac pathology. One of the manifestations of disadaptation in heart failure is a violation of the mechanisms of realization of the intracellular chain "signal-function". The concept of imbalance in the functioning of the adenylate cyclase system and β-adrenergic receptors of the erythrocytes membrane and cardiomyocytes is considered in the pathogenesis of the heart.&#x0D; The study of the dielectric constant (ε՜) of erythrocytes of patients with heart failure was performed using an instrument-recording complex based on microwave dielectrometry of the γ-dispersion region of free water dielectric permittivity. Testing of the β-adrenergic complex of the erythrocyte membrane by specific stimulators, blockers, and modulators was implemented at a fixed frequency of microwave radiofrequency generation (f = 37,7 GHz). Interpretation of the obtained experimental data was that the process of interaction of bioregulators with the biological system is accompanied by an increase or decrease in the relative amount of free water, which leads to a change in the real part of ε՜ complex dielectric constant. This allowed us to visualize the violation of the signal cell system at the molecular level, which manifested itself in the change of integral hydration by ε՜ parameter. It was shown that the change in the dielectric constant of the erythrocyte suspension at risk (patients with hereditary predisposition to dilated and ischemic cardiomyopathy) was significant relative to the dielectric parameters of erythrocyte samples from healthy donors; there was a tendency to block β-adrenergic receptors, with the combined action of adrenaline, PGE2 and cordanum, with Δε՜ = 0,009 ± 0,008 х 10-12 F/m. It should be noted the formation of preconditions for changes in the functioning of the adenylate cyclase system and the development of heart failure in the group at risk, is accompanied by dilated and ischemic cardiomyopathy.&#x0D; The effectiveness of the microwave dielectrometry method for the assessment of violations of adaptation mechanisms through the adenylate cyclase system of the erythrocyte membrane in dilated and ischemic forms of cardiomyopathies is shown. The results of the study are the basis for the introduction of the dielectric constant criterion in the general algorithm of pre-nosological diagnosis of heart failure.

A Nonlinear Radio-Photon Conversion Device

The article analyzes existing materials and structures with quadratic-nonlinear optical properties that can be used to generate a difference frequency in the terahertz and sub-terahertz frequency ranges. The principle of constructing a nonlinear optical-radio converter, based on an optical focon (a focusing cone), is proposed. Based on the assumption that this focon can be implemented from the metal-organic framework (MOF), we propose a technique for modeling its parameters. The mathematical model of the process of propagation and nonlinear interaction of waves inside the focon is based on a simplification of the nonlinear wave equation. Within the framework of the developed model, the following parameters are approximately determined: the 3D gradient of the linear refractive index and the function determining the geometric profile of the focon, which provide a few-mode-based generation of the difference frequency. The achieved theoretical efficiency of radio frequency generation is at least 1%; the proposed device provides a guiding structure for both optical and radio signals in contrast to the known solutions.

Safety and acute performance of paroxysmal and early persistent atrial fibrillation ablation using temperature-controlled, very high power, short duration catheter with a new radiofrequency generator

Abstract Funding Acknowledgements Type of funding sources: Private company. Main funding source(s): Biosense Webster Inc. Background/Introduction The temperature-controlled contact force radiofrequency (RF) ablation catheter (QDM) has 6 thermocouples to maintain target catheter tip temperature and 3 tip microelectrodes for high local signal resolution. It has an enhanced irrigation profile to reduce char formation. Three prospective multicenter trials demonstrated safety and effectiveness of the QDM catheter using very high-power, short duration (vHPSD; 90W/4s), conventional power (CP; ≤50W) or combined modes. These studies were performed with an older RF generator. A new generator was developed to support the full suite of legacy, temperature controlled and multichannel ablation catheters, but has not yet been formally tested in a clinical setting. Purpose Evaluate safety and acute performance of the QDM catheter with the new 90W-enabled generator. Methods This prospective, multicenter study (4 Canadian sites) used vHPSD as primary mode for Pulmonary Vein (PV) isolation with overlapping 3mm lesion tags for anterior, inferior and roof of left atrium. Adjacent, non-overlapping lesions were used posteriorly to avoid esophageal heating. CP mode was used at operator discretion for thicker atrial tissue, touch ups, and non-PV triggers (Figure). Primary endpoint was confirmed entrance block in all PVs after adenosine and/or isoproterenol challenge. Acute procedural and safety data were assessed. Systematic char evaluation was performed. Results Effectiveness analysis included 38/40 subjects with mean 110-day follow up (mean age, 61.7 ± 9.5 years; 63.2% male). Hypertension (47.4%) and congestive heart failure (15.8%) were the most common comorbidities. Fourteen subjects were treated with version V0 of the generator, and 24 subjects were treated using version V1c which included further software adjustments to the power titration, and current response to optimize performance. Combination vHPSD/CP workflow was used for PV isolation in 28 (75.7%) subjects and vHPSD was used solely in 10. A non-study catheter was used in 1 subject during connectivity troubleshooting. Primary endpoint of entrance block confirmation was achieved in 37/38 subjects and in all 37 subjects treated with study catheter only. No incidences of char or device-related adverse events were reported. There were no noted differences in the endpoints evaluated between the V0 and V1c groups. Median (Q1/Q3) RF application times for ablating PVs was 13.0 min (9.0/16.0) for the entire cohort. Median (Q1/Q3) time to achieve PV isolation in vHPSD-only group was 9 (7/12) min, and 14 (11/18) min, respectively. Conclusion(s) Consistent with data from prior 3 clinical studies, QDM catheter with the new 90W-enabled generator demonstrated the acute safety and effectiveness of temperature-controlled AF ablation with short PV ablation time and no char observed.

Impedance spike cut-off enhances safety of CLOSE-protocol guided ablation of atrial fibrillation

Abstract Funding Acknowledgements Type of funding sources: None. Background Catheter ablation (CA) with radiofrequency (RF) energy using the CLOSE protocol has proven safety and efficacy in a large prospective multicenter study (1) with a rate of pericardial tamponade (PT) as low as 0.9%, thus with lower PT risk than reported by previous register data for PVI (2). PT may still become hazardous in the era of uninterrupted anticoagulation and may require urgent surgical repair. Steam pop is the major cause of PT during PVI with RF ablation and is usually preceded by steep impedance rise measured between tissue and tip of the RF catheter. The STOCKERT SMARTABLATE RF Generator as a core part of technology for CLOSE protocol guided PVI offers the opportunity to automatically stop RF energy delivery within 0.5 seconds if catheter impedance rises above a predefined value: impedance spike cut off (ISCO). The standard – manufacturer recommended – value for ISCO is 50 Ohms per 0.5 seconds. Purpose To investigate the effect of reduced ISCO during CLOSE protocol guided catheter ablation of AF on the occurrence of acute PT and pericardial effusion (PE) in a large single center series. Methods We performed CLOSE protocol guided PVI procedures using Biosense Webster CARTO PRIME 3D navigation system, Smarttouch SF ablation catheter, VIZIGO steerable sheath, invasive blood pressure measurement via radial artery. We changed the STOCKERT SMARTABLATE generator settings to ISCO of 25 Ohms per 0.5 seconds. Cut off during ablation by ISCO led the operator to reduce contact force, angulation/orientation of catheter/steerable sheath, changing to jet ventilation if mechanical ventilation was present. A retrospective analysis of all procedures was performed. Investigation for PT by echocardiography was performed for every drop &amp;lt; 90mmHg systolic blood pressure, immediately after and one day post ablation. Statistical analysis was performed on the evaluable population. Results During 31 months of observation we performed 627 CLOSE protocol guided procedures: 409 PVI only, 218 PVI with additional ablations (cavotricuspid isthmus, slow pathway, additional LA lines, ethanol ablation of vein of marshall). We observed 3 (0.5%) PT immediately at the end of the procedure and no additional relevant PE the day after CA. Of the 3 PT, one patient needed urgent surgical repair and two were managed conservatively with pericardiocentesis and retransfusion. Conclusions CLOSE protocol guided PVI is a very effective and safe intervention for treatment of AF. In the multicentre VISITAX trial, the rate of PT was reported with 3 events per 329 patients (0.9%). By reducing ISCO to 25 Ohms per 0.5 seconds, we could half the rate of PT found in the VISITAX trial. The generator cut off at ISCO of 25 Ohms per 0.5 seconds indicates a potentially dangerous position for ablation. Our data are limited due to the retrospective monocentric design and therefore the aformentioned approach should be evaluated prospectively.

Abstract No. : ABS2592: Medial branch block versus medial branch radiofrequency ablation in patients with lumbar facet joint pain

Background and Aims:Lumbar facet joint related pain is reported to have a prevalence of 15-45%.This prospective study was conducted to compare the efficacy of medial branch block with medial branch radiofrequency(RF) ablation in patients with lumbar facet joint pain.Methods:Forty-six participants were randomised to Group-I (n=24) or Group-II (n=22). In Group-I, patients received fluoroscope guided medial branch block with 2ml drug solution comprising of 0.25% bupivacaine plus 10mg of triamcinolone and in Group-II, patients received fluoroscope guided medial branch radiofrequency ablation at a temperature of 80°C for 90 seconds using a RF generator. Patients were followed up for a period of three months. Numeric Rating Scale (NRS) Oswestry Disability Index (ODI) and Roland-Morris Questionnaire (RMQ) score were compared between the groups.Results:NRS and ODI scores were found comparable between the two groups at all the time intervals (p>0.05). Significant reduction (RMQ score was found in Group-II at two weeks (p=0.003) and at one month (p=0.01) ; whereas, at two months and three months the scores were found comparable between the groups(p>0.05). Pain at injection/RF site was significantly less in Group-II (p=0.006). None of the patients reported any serious complications.Conclusion:Both medial branch block and medial branch radiofrequency ablation provide good pain relief and improvement of disability in patients with lumbar facet joint pain. However, improvement in disability is early with medial branch radiofrequency ablation.

Percutaneous radiofrequency ablation of peripheral maxillary nerve: Description of new methodology.

Sir, Maxillary nerve is the second most affected branch in trigeminal neuralgia. It is treated with medical drugs like carbamazepine and baclofen. For long-term pain relief, chemical neurolysis and radiofrequency ablation (RFA) are commonly undertaken, of which RFA results in longer duration of pain relief, shorter onset and increased safety.[1] Chemical neurolysis of maxillary nerve can also result in serious complications.[2] RFA in chronic facial pain is being increasingly used with promising results.[3] We describe two patients where percutaneous RFA of peripheral maxillary nerve was undertaken without fluoroscopic/computed tomography (CT) guidance. A 60-year-old female, a diagnosed case of idiopathic trigeminal neuralgia presented with electric, sharp shooting pain of Numerical rating scale (NRS) score 6/10 in the maxillary area with frequent exacerbations for the last two years. She had inadequate pain relief with oral medications such as carbamazepine, pregabalin, baclofen and tramadol/acetaminophen. For long-term relief, RFA of maxillary nerve via percutaneous approach was planned in the block area of the out-patient department (OPD). Anaesthesia machine, resuscitation equipment, monitor and emergency drugs were available in the OPD block area. After taking consent, intravenous line was secured and monitors (pulse oximetry, non-invasive blood pressure, electrocardiography) were attached. Under aseptic precautions, a 22 G radiofrequency needle (Cosman, 10 cm length, active tip – 1 cm) was inserted via coronoid notch on right side, in supine and neutral head position, after infiltration of local anaesthesia. After hitting lateral pterygoid plate, needle was directed 2–3 mm beyond the pterygoid plate antero-superiorly towards the root of the nose [Figure 1]. To identify maxillary nerve, sensory stimulation (50 Hz, 1 mA) was used to elicit paraesthesia in maxillary area, achieved in first attempt at 0.3 mV. Motor involvement was ruled out by 2 Hz and 2 mA. 1 ml of 1% lignocaine was injected which caused paraesthesia in affected area and was followed by RFA of maxillary neve of 3 cycles at 65° for 60 s followed by injection dexamethasone 4 mg. This patient became pain-free for the next six months. All medications were reduced and tablet baclofen and tramadol were stopped.Figure 1: Infrazygomatic approach of maxillary nerve block (left); Radiofrequency generator for ablation of nerve (right)The second case was a 66-year-old male patient of idiopathic trigeminal neuralgia of one year duration with pain refractory to medical management. Maxillary nerve RFA was performed with similar methodology as above. Sensory stimulation was achieved at 0.4 mV and RFA was performed after excluding motor response. The patient was pain-free for the next eight months and his oral medications were considerably reduced. RFA of peripheral branches of the trigeminal nerve (infraorbital, supraorbital, mental and mandibular nerves) was found equally efficacious to RFA of gasserian ganglion through foramen ovale for trigeminal neuralgia; however, RFA of maxillary nerve was not undertaken in the study.[4] In the commonly practised percutaneous infrazygomatic maxillary nerve blockade,[5] a reliable block requires the patient to report paraesthesia by block needle. Electrical stimulation has reported higher sensitivity of nerve identification than paraesthesia[6] which was utilised for RFA of maxillary nerve via CT- guided percutaneous infrazygomatic approach through foramen rotundum.[7] However, this is invasive, has radiation hazards and requires special area. We propose RFA of maxillary nerve via percutaneous infrazygomatic approach and locating it by electrical stimulation. Added advantages are that it has no radiation hazards, is less invasive and it is an OPD block procedure. Declaration of patient consent The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient has given his consent for his images and other clinical information to be reported in the journal. The patient understands that his name and initials will not be published and due efforts will be made to conceal identity, but anonymity cannot be guaranteed. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.

Medicolegal Sidebar: Are Implant Sales Reps in the Operating Room Legally Untouchable?

Medicolegal Sidebar: Are Implant Sales Reps in the Operating Room Legally Untouchable?

Oxygen atom density in a large reactor powered by four inductively coupled plasma sources

Gradients in O-atom density in metallic plasma reactor useful for rapid surface activation of 3D polymer products have been measured. The reactor of a volume of 150 l was equipped with four inductively coupled plasma sources (ICPS) of (predominantly) oxygen atoms, parallelly coupled with a radio-frequency generator of adjustable power up to 5 kW at 13.56 MHz. Molecular oxygen was continuously introduced into the ICP sources, where it was dissociated upon plasma conditions. The constant pumping of the plasma reactor enabled the effective transfer of O-atoms from the ICP sources, so that their density remained high in the entire chamber even far from plasma sources. The O-atom density was measured across the reactor with a movable catalytic probe calibrated for oxygen. The sophisticated immersible design enabled the O-atom density to exceed 1021 m−3 in the major chamber volume at the pressure of 20 Pa. At this pressure, a uniform plasma in the H-mode was sustained at the total real RF power of 1800 W. Significant gradients in the O-atom density were only detected next to ICP sources' exhausts and in the main chamber's metallic side tubes. Such uniform distribution of O-atoms in a large reactor is advantageous for rapid surface activation of 3D polymer products.

A Novel Biopsy Method Based on Bipolar Radiofrequency Biopsy Needles.

Modern oncology increasingly relies on pathological, molecular, and genomic assessments of biopsied tumor tissue. However, the concern for bleeding complication and malignant seeding severely hinders the application of the biopsy tumor. Here, we developed a 16 G biopsy needle to contain two electrodes insulated from each other and connect to an radiofrequency generator. For evaluating hemostatic efficacy, 50 rabbits were randomly divided into two groups: warfarinization and non-warfarinization group. Two liver biopsies and two splenic biopsies per animal were performed using a 16 G biopsy needle. Each group was further equally divided into five groups according to different hemostatic measures, including non-intervention, embolization using an absorbable gelatin sponge, and ablation by RF with three different needle temperatures (50°C, 70°C, and 90°C). Than, we used VX2 rabbit models (n = 25) and applied the five analogous biopsies to the tumor. The flush fluid from the biopsy needle underwent cytomorphological analysis. Our results that the groups using ablation by RF showed significantly less blood loss than the control group for liver and spleen in both groups (P < 0.001). After RF ablation, thermal coagulation of the tissue surrounding the needle tract was observed on both the macroscopic and histological level. Cytological smears showed that tumor cells were degenerated after RF at 70°C and 90°C. Our findings showed that bipolar RF biopsy needle is a promising tool for reducing hemorrhage after biopsy and avoiding implanting tumor cells in the tract.

Linear Relationship between the Effective Radiation Area and Thermal Images on a Thermochromatic Test Body with 1-MHz Ultrasonic Transducers.

The performance of therapeutic ultrasonic (TUS) devices has a high degree of variability because of the fragility of the equipment (its transducer in particular) and its handling. These facts raise doubts about the effectiveness and safety of treatments employing such devices. Currently there is no simple way to adequately verify the performance of these devices. In our first experiments, we used a thermochromatic test body (typically a cylindrical plate 3.7 cm in diameter and 5.8 mm high) irradiated with therapeutic transducers driven by a standard radiofrequency (RF) generator. Results revealed a linear relationship between the thermal image areas, generated by the transducer's irradiation, and their respective effective radiation areas (ERAs), suggesting a good correlation. With five 3-MHz transducers, our group also observed the linear relationship using commercial TUS RF driving devices. In the present work, we used four 1-MHz transducers with their respective TUS RF driving devices and verified that there is a linear relationship between the thermal images and the ERAs at intensities of 1.0 ± 0.1and 0.5 ± 0.05W/cm2. The linear relationship obtained at both intensities confirms the suggestion that these thermochromatic test bodies can be used as the first evaluation of the ERAs and can monitor their changes with use. Moreover, if a previous assessment of the ERA and transducer intensities is performed, it is possible to follow the variation in ERA simply by monitoring the test body thermal stain.

RF generation using a compact bench gyromagnetic line

The search for new technologies aiming to reach radiofrequency (RF) generation in different manners for diverse ends is a constant demand for several applications. The goal is to develop cost-effective and simpler systems compared to those that already exist. Our motivation is to reach an alternative way of generating RF in pulsed transmission systems employing a gyromagnetic nonlinear transmission line (GNLTL). The GNLTL consists of a ferrite-loaded-coaxial transmission line and can produce a large frequency spectrum with RF conversion efficiency above 10% from about 200MHz up to the frequency of 2-4GHz (S-band) for potential space-based applications. In a GNLTL, the signal amplitude is related to its propagation velocity since the peak voltage travels faster than its portion of lower amplitudes since the ferrite permeability decreases with the current amplitude. As the pulse crest travels faster than its valley, a time reduction happens in the output rise time, called pulse sharpening. Besides, the magnetic moments of ferrite dipoles initially aligned with the axial magnetic bias are displaced from their original position by the azimuthal field generated around the inner conductor by the current pulse, resulting in a damped precession movement. This movement happens along the line length as the current pulse propagates, inducing high-frequency oscillations. In short, the paper's goal is to present the experimental results using a 60-cm gyromagnetic line to provide RF in the GHz range using a solenoid for magnetic bias on a testing bench. Finally, the paper discusses the influence of the azimuthal and the axial magnetic fields on the output signal with the ferrite rings operating in a saturation state during the current pulse propagation.

Thermal Dynamics of a Novel Radio-Frequency Device for Endoscopic Spine Surgery: An Experimental Model.

Experimental study. In this study, the ambient temperature of a radiofrequency (RF) electrode tip was compared and analyzed in terms of products, mode, flow quantity, and flow rate. Endoscopic spine surgery is a widely used operation for degenerative lumbar stenosis and herniated lumbar disc. To perform endoscopic spine surgery, dedicated instruments like a RF generator and electrode are essential. An evaluation system capable of measuring temperature under equal conditions at a certain distance from the electrode tip was manufactured. The distance between the electrode tip and the temperature sensor was set to 1, 5, and 10 mm. The flow quantities of 0, 50, 100, and 150 mL/min and the flow rates of 0, 0.20, 0.53, and 0.80 m/s were compared and statistically analyzed. The temperatures measured in the experiments conducted on the four combinations of RF device showed similar values, and showed differences according to the characteristics of each mode of the RF. As the distance between the electrode tip and the temperature sensor increased, the temperature decreased, and as flow quantity or flow rate increased, the temperature decreased. The maximum temperatures differed significantly according to flow quantity, between flow quantities of 0 and 100 mL/min (P = 0.03) and between 0 and 150 mL/min (P ≤ 0.01). The maximum temperatures also differed significantly between the flow rate of 0 m/s, and the flow rates of 0.20, 0.53, and 0.80 m/s, with P ≤ 0.01 in all three comparisons. This is the first study in which we made a customized RF temperature evaluation system and verified the temperature changes in various environments. When irrigation was performed, we could confirm that the maximum temperature was less than 60°C. Irrigation is considered essential in endoscopic spine surgery. 3.

Radio Frequency and Microwave Photonic Signal Processing and Generation Based on Optical Kerr Micro-Combs

Radio Frequency and Microwave Photonic Signal Processing and Generation Based on Optical Kerr Micro-Combs

Performance Analysis of Resonant-Fin Transistors and Their Application in RF-Circuit Design

Emerging new communication standards like 5G or 6G aggravate the circuit design of radio-frequency generation systems as they constantly increase demand on high bandwidths, low latency, and high spectral purity. The utilization of high-<i>Q</i> oscillators, however, provides a possibility of optimisation of radio-frequency oscillators regarding their phase-noise performance in the overall system. This paper analyses one of the most promising electromechanical resonator devices, the resonant fin transistor with respect to its performance and application in oscillator circuit design. Several investigations regarding its working principle, design trade-offs and limits are carried out in this work. An oscillator circuit design is given for two variants of the resonant fin transistor device together with an outlook on its performance compared to other state-of-the-art radio-frequency oscillator designs. Following the performance analyses conducted throughout this work, the fundamental limit for the <i>Q</i>-factor of this resonator is investigated, challenging the validity of functionality of the resonant fin transistor and its potential for circuit applications.