Conventional RF Research Articles

MSAM: Modular Statistical Analytical Model for MAC and Queuing Latency of VLC Networks under ICS Conditions

Visible Light Communication (VLC) offers distinctive advantages over conventional radio frequency; wide unlicensed spectrum, resistance to electrometric interference and low susceptibility to security risks, are few to name. Excitingly, VLC becomes a cornerstone in several communication systems such as light fidelity, optical camera communication and the Internet of Radio Light. Most of these networks adopt the Carrier Sensing Multiple Access-Collision Avoidance (CSMA-CA) of IEEE 802.15.7, the official standard for the VLC, as a Medium Access Control (MAC) protocol. Motivated by the crucial roles of MAC in shaping the performance of the VLC and the wide variety of operational conditions demanded by the enormous applications, this paper proposes a Modular Statistical Analytical Model (MSAM). The fundamental approach of MSAM is to segregate the interacting stochastic processes imposed by the CSMA-CA protocol into a set of its elementary subprocesses. The MSAM then synthesises these processes in such a way that quantifies their mutual dependency without making a strict assumption on their characteristics; thus, different operational conditions can be assessed without a need to reconstruct the model. Besides, MSAM employs the radiometry and photometry of VLC to derive mathematical expressions describing the hidden and exposed nodes from which the Imperfect Carrier Sensing (ICS) conditions are defined. The MSAM exploits statistical and queuing theorems to model a VLC as a network of G/G/1 queues from which several probability distributions, characterising the operations of VLC from different perspectives, are derived. Inter-departure, queuing, service time and successful service time are the main distributions in conjunction with throughput, total delay, probability of exposed and hidden node collisions, which are the main outputs of MSAM. Validation for the integrity of the MSAM under different scenarios is carried out by conducting a head-to-head comparison between its results and simulation outcomes.

A large beam high efficiency radio frequency neutron spin flipper.

A design for a radio frequency (RF) neutron spin flipper obtained from magneto-static and neutron spin transport simulations is presented. The RF flipper constructed from this design provides a flipping probability of 0.999 or better for a beam size 6cm wide and 15cm high and a wavelength band between 0.4 and 0.6nm. Three permanent magnet guide field sections with air gaps provide a linear field gradient along the beam propagation direction over a large cross-sectional area. An RF oscillator based on coupling the resonant coil of a Hartley oscillator to the excitation coil was developed, which provides a higher current and, thereby, a larger RF amplitude, as compared to a conventional RF power amplifier. Two opaque He3 neutron spin filters were employed to measure the flipping probability of the flipper with very high precision. A spatially uniform flipping probability of 0.9995(2) or higher was measured over the large cross-sectional area neutron guide. This RF neutron spin flipper will be employed in a polychromatic beam reflectometer at the National Institute of Standards and Technology Center for Neutron Research. This design can be applied to other polarized neutron instruments or applications requiring a very high continuous flipping probability of the neutron spin for a large cross-sectional area beam.

Prevalence and predictor factors of persistent pulmonary vein isolation in redo AF ablation procedure

Abstract Funding Acknowledgements Type of funding sources: None. Introduction Atrial fibrillation (AF) catheter ablation is a well-established procedure for the treatment of AF. The cornerstone of AF ablation is the complete isolation of pulmonary veins (PV). However, persistent PV isolation (PVI) is difficult to accomplish, with PV reconnection rates of > 70%. The factors associated with persistent PVI are still uncertain. Purpose To assess the PVI status in patients (pts) undergoing a redo ablation and to determinate the predictors associated with persistent PVI. Methods Consecutive pts who underwent a redo ablation between 2016 and 2020 were identified in a single-centre retrospective study. PVI status was assessed during electrophysiologic study with electroanatomic mapping system. Index procedures included second generation cryoballoon (CB), conventional radiofrequency (RF) before 2018 and CLOSE protocol guided RF ablation after 2018. Persistent PVI was defined by the absence of reconnection of all pulmonary veins. Results We included 83 pts with a mean age of 55,9 ± 11,9 years; 71,1% (n = 59) were male with a mean CHA2DS2-VASc score of 1,14 ±1,0. Seventy-five percent had paroxysmal AF and undergone a redo 35,0 months (±30,9) after the index PVI. Seventeen pts (20,5%) had persistent PVI whereas 66 pts (79,5%) had at least one PV reconnected after the index procedure, with a reconnection rate of 51,8% for right superior and inferior PV, 47,0% for left superior PV and 36,1% for left inferior PV. No statistically significant differences were noticed between pts with persistent and non-persistent PVI in baseline (clinical and echocardiographic) characteristics. Regarding index ablation procedure, persistent PVI occurred more frequently in patients who underwent a "CLOSE" protocol-guided index PVI compared to RF pre-2018 and CB (45,5% vs 16,7%; p = 0,043). Twenty-nine percent of pts with persistent PVI had a "CLOSE" protocol-guided index PVI whereas only 9,1% of non-persistent PVI pts had a "CLOSE" protocol-guided index PVI (p = 0,043). In this cohort, "CLOSE" protocol-guided index PVI was the only predictor of persistent PVI (odds ratio 4.2, 95% confidence interval 1.1-15.9; p = 0.037). Conclusions In patients undergoing redo AF ablation procedures, only 20,5% had persistent PVI. "CLOSE" protocol-guided index PVI presented significantly higher rates of persistent PVI. "CLOSE" protocol-guided index PVI was the only predictor for persistent PVI in patients with AF recurrence requiring a redo procedure.

Redo ablation for atrial fibrillation recurrence post radiofrequency or cryoballoon ablation: a high volume single-centre experience

Abstract Funding Acknowledgements Type of funding sources: None. Introduction Atrial fibrillation (AF) ablation is a well-established procedure for the treatment of AF. The cornerstone of AF ablation is the complete and durable isolation of pulmonary veins (PV) through radiofrequency (RF) or cryoballoon (CB) ablation. However, PVI durability between RF or CB was not yet established, as reablation strategy and outcomes in patients (pt) undergoing a redo ablation. Purpose To compare RF versus CB regarding PVI status, reablation procedure and outcomes in pts undergoing a second procedure. Methods Single-centre retrospective study of consecutive pts who underwent a redo between 2016 and 2020. PVI status was assessed during electrophysiologic study with electroanatomic mapping system. Index procedures included second generation CB, conventional RF before 2018 and CLOSE protocol guided RF ablation after 2018. We assessed time-to-redo, number and location of reconnected PVs, procedural characteristics, acute and long-term outcomes between RF and CB index PVI. Results Seventy-four (55 RF and 19 CB) pts were included, 68,9% were male, most pts had paroxysmal AF (71,6%) and a mean CHA2DS2-VASc score of 1,14 ± 1,0. No statistically significant differences were noticed in clinical and echocardiographic characteristics between pts within RF or CB cohorts. Median time to reablation was significantly longer in the RF cohort (38,6 months ±33,6) compared to CB (17,0 months ±9,5) (p = 0,014). The number of reconnected PV was higher in CB than the RF cohort, although not significant (2,37 ±1,2 vs 1,75 ±1,4;p = 0,080). Right inferior PV was significantly more reconnected in pts within the CB compared to RF group (73,7% vs 45,6%;p = 0,034), without differences in the other PV reconnection rates. Regarding reablation procedure, all pts were submitted to RF-redo. Fluoroscopy time was shorter for CB than RF cohort (7,4 ±2,9 vs 13,3 ±8,4;p = 0,002). There were no significant differences between the type of reablation (PVI only vs PVI plus other lesions or cavotricuspid isthmus ablation), with no difference in overall acute success. After the redo procedure, no differences were observed in recurrence rate in the blanking period and after 91 days from reablation. Nevertheless, time-to-recurrence (>91 days) was longer for RF than CB group (13,4 months ±10,7 vs 4,3 months ±1,5;p = 0,016). There were 2 pts in the RF group that were submitted to a third ablation procedure (p = 0,725). There were no differences between groups in the composite of adverse cardiovascular (CV) outcomes (stroke/transient ischemic attack, emergency room visit for AF, hospitalization for AF or CV death); p = 0,715. Conclusions After the index procedure, reablation occur later in RF than CB cohort. Although the number of reconnected PV were similar between groups, right inferior PV was significantly more reconnected in pts originally treated with CB. After redo, time-to-recurrence was shorter for CB cohort. Recurrence and composite of adverse CV outcomes were similar.

Final results from the EU focal impulse and rotor modulation (E-FIRM) registry

Abstract Funding Acknowledgements Type of funding sources: Private company. Main funding source(s): Abbott Background The exact pathophysiology of how pulmonary vein (PV) triggers initiate or maintain episodes of atrial fibrillation (AF) has been elusive. Catheter ablation at relatively circumscribed areas of rapidly spinning rotors or very rapid focal impulse formation can significantly affect AF. Targeted ablation of these sources using Focal Impulse and Rotor Modulation (FIRM™) shows promise. Purpose To assess the safety and effectiveness of FIRM-guided procedures for the treatment of any type of symptomatic atrial fibrillation (AF). Methods Two hundred and ninety-nine subjects were enrolled in the E-FIRM Registry at 9 clinical sites in Germany and the Netherlands. Subjects were eligible if they had reported incidence of at least 2 documented episodes of symptomatic AF during the preceding 3 months and had failed at least Class I or III anti-arrhythmia drug. Data was collected at enrollment/baseline, procedure, and at 3-, 6-, and 12-month follow-up visits. Results A majority (59.5%, 178/299) had a history of previous ablation, 81.1% (133/164) in the left side, with an average of 1.5 ± 0.8 [range 0, 5] prior ablations. The primary safety endpoint was defined as freedom from procedure related Serious Adverse Events (SAEs) through 7-days and at 12-months. At 7-days, freedom from procedure related SAEs was 94.8% (257/271). At 12-months, freedom from procedure related SAEs was 84.4% (184/218). There were no deaths. Acute effectiveness success, defined as the elimination of all identified rotors, occurred in 64.0% (165/258) of treated patients. All patients for which data was reported had at least 1 rotor identified. The most common regions to find rotors were the lateral wall of the right atrium, the anterior/septal wall of the left atrium, and the posterior inferior region of the left atrium. 75.2% (194/258) of patients had at least one rotor identified in the right atrium, and 84.1% (217/258) of patients had at least one rotor identified in the left atrium. Success was defined as two sequential endpoints: single procedure freedom from AF recurrence at 3-months and single procedure freedom from AF recurrence. At 12-months, success was achieved in 46.4% (13/28) Paroxysmal, 42.9% (87/203) Persistent, and 0% (0/9) Long Standing AF subjects. Conclusions: Since acute success was reported as being achieved in only ∼2/3 of the treated subjects, it is possible that the full potential benefit of the FIRM-guided ablation was hidden in this evaluation of the full cohort. Considering the previous ablation and disease history of subjects, a single-procedure success rate at 12-months over 40% was considered a positive result. Based on these results, FIRM-guided RF ablation in conjunction with conventional RF ablation practices is both a safe and effective treatment strategy for patients with symptomatic AF.

Colloidal PbS Quantum Dots for Visible-to-Near-Infrared Optical Internet of Things

The emergence of optical Internet of Things (optical-IoT) for sixth-generation (6G) networks has been envisaged to relieve the bandwidth congestion in the conventional radio frequency (RF) channel, and to support the ever-increasing number of smart devices. Among the plethora of device innovations deemed essential for fortifying the development, herein we report on the visible-to-near-infrared color-conversion luminescent-dyes based on lead sulphide quantum dots (PbS QDs), so as to achieve an eye-safe high-speed optical link. The solution-processed PbS QDs exhibited strong absorption in the visible range, radiative recombination lifetime of 6.4 $\mu$ s, as well as high photoluminescence quantum yield of up to 88%. Our proof-of-principle demonstration based on an orthogonal frequency-division multiplexing (OFDM) modulation scheme established an infrared data transmission of 0.27 Mbit/s, readily supporting an indoor optical-IoT system, and shed light on the possibility for PbS-integrated transceivers in supporting remote access control of multiple nodes. We further envisaged that our investigations could find applications in future development of solution-processable PbS-integrated luminescent fibers, concentrators, and waveguides for high-speed optical receivers.

Studying the Double Rayleigh Backscattering Noise Effect on Fiber-Optic Radio Frequency Transfer

We report the effect of the double Rayleigh backscattering (DRB) noise, in which the interference of the signal light with the double Rayleigh backscattered light, on the fiber-optic radio-frequency (RF) transfer system. Here, we theoretically analyze and experimentally demonstrate that the DRB noise within the fiber link will become the dominative noise on the fiber-optic RF transfer system once narrow linewidth lasers are used. The strong DRB noise is experimentally confirmed through the measurement of the effect of the coherent interference term of the signal light and the double Rayleigh backscattered light on the 100 km RF transfer system. Our results provide evidence that the conventional RF transfer technique with the telecommunications-grade lasers, in which the chromatic dispersion effect in the single-mode fiber is compensated by dispersion compensation fibers (DCFs), could be the better choice for high-performance RF transfer.

Lesion size and adjacent tissue damage assessment with high power and short duration radiofrequency ablation: comparison to conventional radiofrequency ablation power setting.

There is increased interest in creating high-power short duration (HPSD) ablation lesions in the field of atrial fibrillation (AF) radiofrequency ablation (RFA). We evaluated the lesion characteristics and collateral damage using two separate RFA protocols setting (HPSD: 50W and 7s vs control: 25W and 30s) in vitro model. Sixteen freshly killed porcine hearts were obtained, and the atrium and ventricle slabs were harvested for ablation. The each slabs were placed in a tissue bath with circulating 0.9% NaCl at maintained temperature 37°C. RFA was performed with 4mm tip irrigated force sensing catheter. All lesions were ablated under recording the electrical parameters using with Ensite Navx system (St. Jude Medical, St. Paul, Minnesota). After RFA, lesion characteristics were assessed for each lesion. Thirty-five lesions were made for each ablation protocol (total 70 lesions for analysis). Ablation parameters were similar between two groups (HPSD vs control; impedance drop (Ω): 34.2 ± 13.1 vs 36.1 ± 8.65 P = 0.49, contact force (g): 13.9 ± 4.37 vs 14.6 ± 5.09, P = 0.51, lesion size index: 4.8 ± 0.52 vs 4.73 ± 0.59, P = 0.62). Although the lesion volume was similar, the HPSD ablation creates wider but more shallower lesions compared to control group (HPSD vs control; lesion volume: 29.6 ± 18.1mm3 vs 35.5 ± 17.1mm3 P = 0.16, lesion diameter: 4.98 ± 0.91mm vs 4.45 ± 0.74mm P = 0.0095, lesion depth: 2.2 ± 0.76mm vs 2.8 ± 1.56mm P = 0.046). Of these, 38 lesions were assessed for adjacent tissue damage and adjacent tissue damages were more frequent seen in control group (HPSD vs control; 1/19 (5.26%) vs 6/19 (31.5%), P = 0.036). Effective lesions were made with HPSD, thereby reducing RFA procedure time. Although the lesion volume was similar between two groups, collateral damage was less seen in HPSD group attributed by lesion characteristics.

A 0.1–4.0-GHz Inductorless Direct-Sequence Spread-Spectrum-Based Ground-Penetrating Radar System-on-Chip

This letter presents a 0.1-4.0-GHz broadband serial direct-sequence spread-spectrum (DS/SS)-based inductor-free ground-penetrating radar (GPR) system-on-chip (SoC). A time-domain digital correlation-based time-of-flight measurement is employed for radar ranging instead of using a frequency chirp or pulse, which allows a higher degree of flexibility. With no conventional RF up/down conversion present, the radar offers complete programmability over frequency and bandwidth (BW) up to 4.0 GHz. In-field GPR test with actual rover prototype is performed to validate the capability and characterize the overall performance of the DS/SS radar system. Implemented in 28-nm CMOS, the demonstrated prototype radar SoC offers a fine resolution of 3.75 cm and consumes 46.2 mW from 1-V supply. This makes it suitable for low-power applications such as planetary exploration.

High-throughput injection–acceleration of electron bunches from a linear accelerator to a laser wakefield accelerator

Plasma-based accelerators (PBAs) driven by either intense lasers (laser wakefield accelerators, LWFAs) or particle beams (plasma wakefield accelerators, PWFAs), can accelerate charged particles at extremely high gradients compared to conventional radio-frequency (RF) accelerators. In the past two decades, great strides have been made in this field, making PBA a candidate for next-generation light sources and colliders. However, these challenging applications necessarily require beams with good stability, high quality, controllable polarization and excellent reproducibility. To date, such beams are generated only by conventional RF accelerators. Therefore, it is important to demonstrate the injection and acceleration of beams first produced using a conventional RF accelerator, by a PBA. In some recent studies on LWFA staging and external injection-acceleration in PWFA only a very small fraction (from below 0.1% to few percent) of the injected charge (the coupling efficiency) was accelerated. For future colliders where beam energy will need to be boosted using multiple stages, the coupling efficiency per stage must approach 100%. Here we report the first demonstration of external injection from a photocathode-RF-gun-based conventional linear accelerator (LINAC) into a LWFA and subsequent acceleration without any significant loss of charge or degradation of quality, which is achieved by properly shaping and matching the beam into the plasma structure. This is an important step towards realizing a high-throughput, multi-stage, high-energy, hybrid conventional-plasma accelerator.

Metamaterial-Inspired Radiofrequency (RF) Shield With Reduced Specific Absorption Rate (SAR) and Improved Transmit Efficiency for UHF MRI.

To prevent the interferences between radiofrequency (RF) coils and other components in the magnetic resonance imaging (MRI) system such as gradient coils, it is essential to place an RF shield between the RF coils and gradient coils. However, the induced currents on conventional RF shields have negative influences on the RF coil performance. To reduce these influences, metamaterial absorbers (MA), a class of metamaterials exhibiting nearly unity absorption rate for the incident electromagnetic fields, can be employed for the design of a novel RF shield. However, the adoption of metamaterials in MRI systems is usually problematic because of the bulkiness of the metamaterial structure. In this work, capacitors and metallic interconnectors are used to miniaturize the MA so that the unit MA cell can operate at the Larmor frequencies of 7T and 9.4T MRI and stay compact. This MA-RF shield is used to improve the transmit efficiency of RF surface coils and reduce the specific absorption rate (SAR) in the region of interest (ROI). It is successfully demonstrated by simulations and experiments that, compared with conventional RF shield structure, the transmit efficiency can be enhanced by more than 32% and the peak SAR value can be reduced by 22% using the MA-RF shield. Moreover, it is observed that the transmit field penetration is improved when the surface coil is used with the MA-RF shield. This proof-of-concept study suggests a new practical way for the utilization of metamaterials in ultra-high field MRI applications.

A magnetic‐free in‐band full‐duplex RF front‐end with antenna balancing structure

In this article, a design of magnetic-free in-band full-duplex (IBFD) RF front-end with antenna balancing structure is presented. The proposed magnetic-free IBFD RF front-end consists of 3 dB hybrid couplers, a Wilkinson power divider, two transmitter (Tx) antennas, and two receiver (Rx) antennas. The proposed IBFD RF front-end can be implemented and integrated at high frequencies because all the components used in the circuit are non-magnetic devices. Proposed IBFD RF front-end eliminated the 3-dB Tx insertion-loss of the Balun and transformer in conventional IBFD RF front-ends using antenna balancing structure. Moreover, there is no noise figure degradation at Rx because it realized only a passive circuit. The mathematical analysis of the cancellation characteristics between two different signals with magnitude and phase difference variations according to the normalized frequencies is presented. Accordingly, the broadband out-of-phase balancing power splitter and the antenna balancing structure are adopted to achieve broadband SIC. In order to verify the electrical performances of the proposed magnetic-free IBFD RF front-end, it was implemented at the 2.5 GHz WiMax frequency band. When the fabricated IBFD RF front-end was operated with antenna balancing structure, the measurement results show that the 60 dB SIC bandwidth and maximum SIC were 113 MHz (2.446 - 2.559 GHz) and 75.6 dB, respectively.

A focused very high energy electron beam for fractionated stereotactic radiotherapy

An electron beam of very high energy (50–250 MeV) can potentially produce a more favourable radiotherapy dose distribution compared to a state-of-the-art photon based radiotherapy technique. To produce an electron beam of sufficiently high energy to allow for a long penetration depth (several cm), very large accelerating structures are needed when using conventional radio-frequency technology, which may not be possible due to economical or spatial constraints. In this paper, we show transport and focusing of laser wakefield accelerated electron beams with a maximum energy of 160 MeV using electromagnetic quadrupole magnets in a point-to-point imaging configuration, yielding a spatial uncertainty of less than 0.1 mm, a total charge variation below 1 % and a focal spot of 2.3 times 2.6;{text {mm}}^2. The electron beam was focused to control the depth dose distribution and to improve the dose conformality inside a phantom of cast acrylic slabs and radiochromic film. The phantom was irradiated from 36 different angles to obtain a dose distribution mimicking a stereotactic radiotherapy treatment, with a peak fractional dose of 2.72 Gy and a total maximum dose of 65 Gy. This was achieved with realistic constraints, including 23 cm of propagation through air before any dose deposition in the phantom.

Recent Progress in Radio-Frequency Sensing Platforms with Graphene/Graphene Oxide for Wireless Health Care System

In the past decade, graphene has been widely researched to improve or overcome the performance of conventional radio-frequency (RF) nanodevices and circuits. In recent years, novel RF bio and gas sensors based on graphene and its derivatives, graphene oxide (GO) and reduced graphene oxide (rGO), have emerged as new RF sensing platforms using a wireless remote system. Although the sensing schemes are still immature, this review focuses on the recent trends and advances of graphene and GO (rGO)-based RF bio and gas sensors for a real-time and continuous wireless health care system.

Adjustable RF Transmitter Head Coil: Improving Transmit Efficiency With SAR Management for 7-T Magnetic Resonance Imaging

In ultrahigh field magnetic resonance imaging (MRI) using a static magnetic field over 7 T, the inhomogeneity in the time-varying magnetic field ( $B_{1}$ ), which is caused by its short wavelength, is mitigated by using a multichannel radio frequency (RF) coil as an antenna. However, the conventional multichannel RF coil has a fixed configuration; consequently, its transmit efficiency (TE) changes according to the head shape of the patient. In this study, a geometrically adjustable eight-channel RF transmitter head coil for 7-T MRI was proposed. All resonators and supporting structures (called bridges) in the coil have interlocking teeth at their sides, allowing each channel to adjust its geometric location according to the head shape of the patient. Scenarios for conventional and proposed coils in three different configurations were simulated and compared in terms of the transmitted component of the $B_{1}$ field ( $B_{1}^{+}$ field) and specific absorption rate (SAR) maps. The simulation results indicate that, for a given configuration and head shape, the TE of the proposed coil was higher than that of the conventional coil, while the SAR efficiency remained unchanged. Furthermore, the S-parameter matrix of the proposed coil and the measured $B_{1}$ field produced by the two channels facing each other show that the proposed coil resonates at 298 MHz with acceptable mutual coupling and effectively improves the $B_{1}$ field intensity. Moreover, the obtained signal-to-noise ratio (SNR) maps and magnetic resonance (MR) images prove that the proposed coil is an efficient candidate for an RF transmitter or transceiver head coil used in 7-T MRI.

High-power short duration vs. conventional radiofrequency ablation of atrial fibrillation: a systematic review and meta-analysis.

We sought to compare the effectiveness and safety of high-power short-duration (HPSD) radiofrequency ablation (RFA) with conventional RFA in patients with atrial fibrillation (AF). MEDLINE, Cochrane, and ClinicalTrials.gov databases were searched until 15 May 2020 for relevant studies comparing HPSD vs. conventional RFA in patients undergoing initial catheter ablation for AF. A total of 15 studies involving 3718 adult patients were included in our meta-analysis (2357 in HPSD RFA and 1361 in conventional RFA). Freedom from atrial arrhythmia was higher in HPSD RFA when compared with conventional RFA [odds ratio (OR) 1.44, 95% confidence interval (CI) 1.10-1.90; P = 0.009]. Acute PV reconnection was lower (OR 0.56, P = 0.005) and first-pass isolation was higher (OR 3.58, P < 0.001) with HPSD RFA. There was no difference in total complications between the two groups (P = 0.19). Total procedure duration [mean difference (MD) -37.35 min, P < 0.001], fluoroscopy duration (MD -5.23 min, P = 0.001), and RF ablation time (MD -16.26 min, P < 0.001) were all significantly lower in HPSD RFA. High-power short-duration RFA also demonstrated higher freedom from atrial arrhythmia in the subgroup analysis of patients with paroxysmal AF (OR 1.80, 95% CI 1.29-2.50; P < 0.001), studies with ≥50 W protocol in the HPSD RFA group (OR 1.53, 95% CI 1.08-2.18; P = 0.02] and studies with contact force sensing catheter use (OR 1.65, 95% CI 1.21-2.25; P = 0.002). High-power short-duration RFA was associated with better procedural effectiveness when compared with conventional RFA with comparable safety and shorter procedural duration.

DeepControl: 2DRF pulses facilitating inhomogeneity and B0 off-resonance compensation in vivo at 7 T.

Rapid 2DRF pulse design with subject-specific inhomogeneity and B0 off-resonance compensation at 7 T predicted from convolutional neural networks is presented. The convolution neural network was trained on half a million single-channel transmit 2DRF pulses optimized with an optimal control method using artificial 2D targets, and B0 maps. Predicted pulses were tested in a phantom and in vivo at 7 T with measured and B0 maps from a high-resolution gradient echo sequence. Pulse prediction by the trained convolutional neural network was done on the fly during the MR session in approximately 9 ms for multiple hand-drawn regions of interest and the measured and B0 maps. Compensation of inhomogeneity and B0 off-resonances has been confirmed in the phantom and in vivo experiments. The reconstructed image data agree well with the simulations using the acquired and B0 maps, and the 2DRF pulse predicted by the convolutional neural networks is as good as the conventional RF pulse obtained by optimal control. The proposed convolutional neural network-based 2DRF pulse design method predicts 2DRF pulses with an excellent excitation pattern and compensated and B0 variations at 7 T. The rapid 2DRF pulse prediction (9 ms) enables subject-specific high-quality 2DRF pulses without the need to run lengthy optimizations.

An Optical Communication Approach for Ultra-High-Speed Train Running in Evacuated Tube: Potentials and Challenges

Modern society demands a new kind of ultra-high-speed ground transportation, which can be achieved by evacuated tube transportation (ETT). However, conventional radio frequency communication is faced with serious Doppler spread and frequent handovers in such ultra-high-speed environments. Thus, in this article, a novel wireless communication system suitable for ETT is proposed, which is based on optical wireless communication (OWC). This system meets the requirements of ultra-high speed, high reliability, and low latency, while the OWC can effectively avoid Doppler spread in metal tubes by nature. In addition, a system structure with seamless connection is designed to improve system reliability by providing communication redundancy. Furthermore, a vehicle-centric handover-free method is proposed, which can effectively reduce the number of handovers, thereby decreasing system latency. Finally, the challenges and future research trends for ultra-high-speed trains are highlighted to provide insights on the potential future work for researchers in this field.

Radiofrequency Treatment of Idiopathic Trigeminal Neuralgia (Conventional vs. Pulsed): A Prospective Randomized Control Study.

Background:Idiopathic trigeminal neuralgia (TGN) is a chronic pain disorder causing unilateral, severe brief stabbing recurrent pain in the distribution of one or more branches of the trigeminal nerve. Conventional radiofrequency (CRF) and pulsed radiofrequency (PRF) are two types of minimally invasive treatment. CRF selectively ablates the part of ganglion to provide the relief, but it has been found to be associated with some side effects such as dysesthesia or sensory loss in 6%–28% and loss of corneal reflex in 3%–8% of patients. PRF is a comparatively newer modality which is a nondestructive and neuromodulatory method of delivering radiofrequency energy to the gasserian ganglion to produce a therapeutic effect.Aims:We aimed to compare the efficacy of CRF with long-duration, fixed voltage PRF in the treatment of idiopathic TGN.Setting:This study was conducted in a tertiary care center research institute.Study Design:This was a prospective randomized trial.Materials and Methods:Twenty-seven adult patients of TGN were included in the study and randomly allocated into two groups (CRF and PRF). All procedures were performed operation suite with C-arm fluoroscopic guidance. Both, pre- and postprocedure, the patients were assessed for pain on the Visual Analog Scale (VAS) and Barrow Neurological Institute (BNI) Pain Intensity Scale at 1 week and thereafter at 1, 2, 3, and 6 months. Patients with a BNI score ≥4 after 1 month were considered a failure and offered other modes of treatment. A reduction in VAS score ≥50% and a BNI score <4 were considered as effective.Statistical Analysis:Discreet variables were recorded as proportions, ordinal variables and continuous variables with non-Gaussian distribution as medians with interquartile range, and continuous variables with Gaussian distribution as mean ± standard deviation. Association between ordinal variables was tested by Fisher's exact test/Chi-square test whenever appropriate. Equality of means/median was tested by using paired/unpaired t-test or nonparametric tests depending upon the distribution of data. P ≤ 0.5 was considered statistically significant. Data analysis was performed using STATA version 13.04 windows.Results:Efficacy in terms of decrease in VAS ≥50% at 1 month was 33.33% and 83.33% in the PRF and CRF groups, respectively, which was statistically significant(P = 0.036). Effective reduction in BNI scores at the 7th day, 1 month, and 2 months postprocedure was evaluated and found in 41.67% and 83.33% of patients in the PRF and CRF groups, respectively, which was statistically insignificant (P = 0.089). There was a statistically significant reduction in BNI scores in PRF and CRF group patients at 3 and 6 months (at 3 months, 33.33% and 83.33%, P = 0.036 and at 6 months, 25% and 83.33%, P = 0.012). In the CRF group, mild hypoesthesia was evident in three patients which improved by the end of 1 month while no side effects were seen in the PRF group.Conclusion:CRF is a more effective procedure to decrease pain in comparison to long-duration, fixed voltage PRF for the treatment of idiopathic TGN. Although the side effects are more with CRF, they are mild and self-limiting.

The effectiveness of conventional radiofrequency ablation for chronic plantar heel pain due to heel spur.

The purpose of this study was to investigate the effectiveness of conventional radiofrequency (CRF) ablation treatment on chronic plantar heel pain due to heel spur. A total of 20 patients with heel spur who did not respond to conservative treatments were recruited for the study. Under fluoroscopy guidance, CRF was performed to three points at the top, above, and below the heel spur in the longitudinal plane of the foot. Pain intensity, the pressure pain threshold (PPT), and functional status were assessed using a visual analog scale (VAS), pressure algometers, and the Foot Function Index (FFI). All measurements were taken before the procedure, as well as 1, 3, and 6 months following the procedure. CRF was applied to 20 patients - 16 (80%) females and 4 (20%) males. Their mean age was 51.40+-8.10 years, the mean body mass index was 33.80+-5.47 kg/m2, the mean duration of symptoms was 18.30+-9.02 months, and pes planus was present in 5 patients (25%). A statistically significant decrease was observed in VAS score and PPT and FFI measurements at the 1st, 3rd, and 6th month following CRF compared to before CRF (p<0.001). CRF is an effective, safe, minimally invasive method to reduce pain severity in patients with chronic heel pain due to heel spur in the short (0-3 months) and intermediate term (3-6 months).