Repeater Coils Research Articles

Load-Independent Wireless Power Transfer System for Multiple Loads Over a Long Distance

In this paper, a novel long-distance wireless power transfer (WPT) system using repeater coils is proposed to provide power supplies for the driver circuits in high-voltage applications, such as flexible alternative current transmission systems. Different from most of the existing wireless repeater systems where the load is only connected to the last coil and the repeater coils function solely as power relays, in the proposed system, multiple loads are powered by the repeaters. The repeater coils transfer power not only to the subsequent coils but also to the loads connected to them. Dual coil design is proposed for the repeaters with which load-independent characteristics are obtained with a suitable design of coupling coefficients. As a result, the load power can be easily adjusted without affecting each other. Load current characteristics and system efficiency have been analyzed in detail. The power transfer capability of the proposed system is illustrated for different coil quality factors and coupling coefficients. An experimental setup with 10 loads has been built to validate the effectiveness of the proposed long-distance WPT system. The maximum reachable system efficiency is about 84%.

A Load-Independent LCC-Compensated Wireless Power Transfer System for Multiple Loads With a Compact Coupler Design

This article proposes a novel wireless power transfer (WPT) system for multiple loads. Multiple coils are used as power repeaters to enhance the power transfer capability over a long distance and each power repeater corresponds to a load. The inductor-capacitor-capacitor (LCC) compensation method is used for each repeater coil in the system, which ensures load-independent currents flowing through the loads. Thus, flexible power control can be achieved for all the loads without affecting each other. In order to save space, the compensation coil is integrated with the repeater coil to realize a compact design. Bipolar coils are used for both the repeater coil and compensation coil. The undesirable coupling coefficient between the repeater coil and its compensation coil can be eliminated by putting them perpendicularly. The compensation coil is not only used to achieve resonant condition for the system, but also transfers energy to the next repeater coil via the magnetic coupling between them. The operational principle has been explained in detail. An experiment platform with six loads has been built and the experimental results are provided to validate the effectiveness of the proposed WPT repeater system. The maximum efficiency can reach 86.6%.

Quantitative Comparison of Wireless Power Transfer Using HTS and Copper Coils

Wireless power transfer (WPT) technology, especially using the magnetic resonance coupling to transfer the electric power has gained more attention recently. Due to ultra-low electrical resistivity below the critical current, the current density and quality factor of the superconducting wires are much higher than that of the traditional copper wires. Therefore, the transferring performance can be improved greatly. The superconducting wires have been adopted as the power coil, transmitter coil, repeater coil, and receiver coil, respectively. In this paper, performances of WPT systems partially and fully equipped with superconducting wires are quantitatively compared. Firstly, the classical WPT system with four coils has been presented. Then, superconducting coils and cooling facility for WPT systems are discussed. Lastly, by using the finite element method, transferring performance of the WPT system under different scenarios are intensively evaluated and compared.

A Multi-Load Wireless Power Transfer System With Series-Parallel-Series Compensation

This letter proposes a novel wireless power transfer (WPT) system with repeater coils for multiple loads. Every two repeater coils form a repeater unit where one is used to receive power from its preceding unit and the other transmits power to the subsequent unit. Each load is connected to a repeater unit and multiple loads can be powered with several repeater units. The two coils in the same repeater unit are both bipolar ones, which are placed perpendicularly so that the magnetic coupling between them can be eliminated. In order to obtain independent power control of all the loads, the series-parallel-series compensation method is adopted for each repeater unit. With a proper resonant condition proposed in this letter, the constant load current can be obtained for all the loads when neglecting the coils’ parasitic resistances. An experimental setup has been constructed and the effectiveness of the proposed multi-load WPT system is validated by the experimental.

A Study on an Optimal Coil Positioning in a Wireless Power Transfer System with a Function of Human Tracking

The magnetic resonant wireless power transfer system with a function of human tracking has been proposed in order to supply the electrical energy to a power assist robot suit. A simple and fast algorithm using the gradient ascent to calculate optimal coil position based on the position and attitude of a receiver coil was developed. Simulation results showed that the optimal coil positions and attitudes of the transfer and repeater coils were calculated within 0.1 s. Even the receiver coil moved with a speed of 1 m/s, the algorithm could give the coil positions within the sufficient time to keep the high transfer efficiency. The simulated optimal coil position was compared with the experimentally measured optimal position and they showed good agreement each other.

Duodenal Variceal Bleeding: A Rare Complication of Portal Hypertension

IntroductionDuodenal varices are a rare complication of portal hypertension and are labeled as ectopic varices. These are portosystemic collaterals in locations besides the gastroesophageal region and represent 2-5% of all variceal bleeding. Duodenal varices represent 17% of these bleeds. Although they are rare, duodenal varices are challenging to treat and often fatal. Case A 57 year-old female patient with a history of decompensated alcoholic cirrhosis initially presented to an outside hospital for melena. Esophagogastroduodenoscopy (EGD) done there reported an ulcer in the second part of duodenum that was treated with three hemoclips. She was then transferred to our institution for further management. She had melena on presentation resulting in hemodynamic instability. Initial hemoglobin was 8.6, which quickly declined to 6.0. Urgent EGD showed small esophageal varices, portal hypertensive gastropathy and bright red blood in the first and second parts of duodenum without an actively bleeding source readily identifiable. Shortly after the procedure she developed additional melenic bowel movements. On review of imaging, duodenal varices were identified incidentally on computed tomography of the abdomen. She subsequently underwent emergent TIPS and coil embolization of cecal and a duodenal varices. Unfortunately, over the next eight days, she continued to have recurrent bleeding episodes despite upsizing of TIPS and cyanoacrylate injection directly into the duodenal varix. The bleeding ceased after a repeat coil embolization of residual duodenal varices. The patient subsequently developed fungemia and septic shock, shortly after which she passed away. Conclusion Duodenal varices are usually seen in either the first or second part of the duodenum. They arise due to portosystemic communication via veins of Retzius. Due to its rarity, there have been no randomized trials on the management of this condition and treatment guidelines have not been established. Case reports showed various treatment modalities including sclerotherapy, varix ligation, resection and portocaval shunt. Despite this, mortality rate remains as high as 40%. Bleeding from duodenal varices should always be considered in the differential diagnosis of a patient with portal hypertension who presents with upper gastrointestinal bleeding.1995_A Figure 1 No Caption available.1995_B Figure 2 No Caption available.1995_C Figure 3 No Caption available.

Circuit Analysis and Characterization of Contactless Power Transfer System with Variable Impedance

SUMMARYA contactless power transfer system using a repeater coil (repeater Coil topology) has been proposed as a method of suppressing overcurrent without power control during misalignment or no‐load. By installing a repeater coil between the primary and secondary coils, it is possible to increase the input impedance in the case of misalignment of the secondary coil or no‐load condition. In addition, another contactless power transfer system using primary parallel and secondary series resonance capacitors (PS capacitor topology) has been proposed. In the PS capacitor topology, the input impedance can be increased during misalignment of the secondary coil or no‐load condition similar to the repeater coil topology. In this paper, we evaluated the characteristics of both these topologies. First, we conducted a circuit analysis of the repeater coil topology and proposed a design method. In addition, we theoretically clarified the characteristic difference of the two topologies and experimentally evaluated the characteristics.

Readout Distance Enhancement of the Passive Wireless Multi-Parameter Sensing System Using a Repeater Coil

A repeater coil is used to extend the detection distance of a passive wireless multi-parameter sensing system. The passive wireless sensing system has the ability of simultaneously monitoring three parameters by using backscatter modulation together with channel multiplexing. Two different repeater coils are designed and fabricated for readout distance enhancement of the sensing system: one is a PCB (printed circuit board) repeater coil, and the other is a copper wire repeater coil. Under the conditions of fixed voltage and adjustable voltage, the maximum readout distance of the sensing system with and without a repeater coil is measured. Experimental results show that larger power supply voltage can help further increase the readout distance. The maximum readout distance of the sensing system with a PCB repeater coil has been extended 2.3 times, and the one with a copper wire repeater coil has been extended 3 times. Theoretical analysis and experimental results both indicate that the high Q factor repeater coil can extend the readout distance more. With the copper wire repeater coil as well as a higher power supply voltage, the passive wireless multi-parameter sensing system finally achieves a maximum readout distance of 13.5 cm.

Optimization of a Wireless Power Transfer System With a Repeater Against Load Variations

Power transfer efficiency (PTE) and transferred power (TP) are the key performance indices for the design of wireless power transfer (WPT) systems. An optimization method for WPT system with the use of a repeater is presented to enhance both PTE and TP. A tuning technique is investigated for the performance improvement against load variations. The self-resonance frequencies of transmitter, receiver, and repeater coils, and the operating frequency can be optimized to improve the load characteristics. The analytical approach presented in this paper is found to be capable of reaching the global optimum solution for a given design condition. Theoretical analysis is supported with the numerical and experimental results.

可変インピーダンスを考慮した非接触給電システムの回路解析と特性評価

A contactless power transfer system using a repeater coil (Repeater Coil topology) has been proposed as a method of suppressing overcurrent without power control during misalignment or no-load. By installing a repeater coil between the primary and secondary coils, it is possible to increase the input impedance in the case of misalignment of the secondary coil or no-load condition. In addition, another a contactless power transfer system using primary parallel and secondary series resonance capacitors (PS Capacitor topology) has been proposed. In the PS Capacitor topology, the input impedance can be increased during misalignment of the secondary coil or no-load condition similar to the Repeater Coil topology. In this paper, we evaluated the characteristics of both these topologies. First, we conducted a circuit analysis of the Repeater Coil topology and proposed a design method. In addition, we theoretically clarified the characteristic difference of the two topologies and experimentally evaluated the characteristics.

Trading scalpels for sheaths

The skill set of the acute care surgeon can be expanded by formal training. We report the first series of traumatic vascular injury (TVI) treated by acute care surgeons trained in endovascular techniques (ACSTEV). We retrospectively reviewed patients admitted to our trauma center with TVI over 5 months who survived for more than 24 hours and had catheter diagnosis and/or therapy by ACSTEV. Demographics, admission data, and outcomes were reviewed. Follow-up ranged from 0 day to 150 days. Most patients were male (63%) and sustained blunt mechanism (91%). Mean (SD) age was 48.2 (21.9) years, and mean (SD) Injury Severity Score was 32.1 (11.8). Mean (SD) admission systolic blood pressure, heart rate, Glasgow Coma Scale (GCS) score were 126.12 (30.4) mm Hg, 101.21 (28.2) beats per minute, and 10.8 (4.73), respectively. Forty-six patients underwent 48 endovascular procedures for TVI: 32 angiograms and 16 venograms were obtained. Two pelvic angiograms and one aortic arch angiogram were negative and required no treatment. One superficial femoral artery arteriogram showed minor luminal defects requiring anticoagulation only. Pseudoaneurysms were found in 17 vessels, vessel truncation in 4, active extravasation in 5, stenosis in 1, and dissection with thrombus in 1. Four patients had resuscitative endovascular balloon occlusion of the aorta performed before catheter intervention for pelvic hemorrhage. Procedures included aortic repair (4), pelvic embolization (13), splenic embolization (5), lumbar artery embolization (1), bronchial artery embolization (1), profunda artery embolization (1), common carotid artery stent (1), celiac artery stent (1), inferior vena cava filter placement (14) and retrieval (2), and pharmacomechanical thrombolysis (1). Treatment material included coils (12), Gelfoam (4), and nitinol plugs (3). No procedural or device-related complications occurred. Mortality was 14.7% unrelated to any endovascular procedure. One patient had repeat coil embolization of a pelvic pseudoaneurysm on postoperative Day 7. ACSTEV can safely treat TVI with good success. We performed nearly 10 procedures per month underscoring the role of the ACSTEV for training and care of TVI in a high-volume trauma center. Therapeutic study, level V.

Subarachnoid hemorrhage with blister aneurysms: Endovascular management.

Blister aneurysms of are rare lesions representing a real challenge for diagnosis and management. They typically show small size, hemispherical shape, fragile wall, broad neck, and are arising from non-branching sites of intracranial arteries. We retrospectively reviewed all aneurysms treated at our institution. Seventeen patients (6 male, 11 female) with 17 blister aneurysms were identified (mean age 53.3, range 41-63 years). Clinical, procedural, angiographic data as well as follow up data were evaluated. All patients presented with aneurysmal subarachnoid hemorrhage. Majority of the blister aneurysms were located in ICA while 1 was located at posterior cerebral artery, 1 at vertebral and 1 involving basilar artery. All patients were treated using single or overlapping stents and if possible additional coiling. There was no intra-operative rupture. Good outcome (mrs 0-2) was seen in 14 patients. Poor clinical outcome (mrs 3-5) was seen in 2 patients due to vasospasm induced ischemic deficits at discharge, both of them improved on follow up (mrs 1 on follow up). There were 3 mortalities, One patient died of rebleeding while other 2 died due to SAH induced complications. Follow-up angiography was available in 16 patients (one patient died before follow up angiogram) and revealed complete or near complete aneurysm occlusion in 11, incomplete obliteration in 1 and no change in 2 cases. Two cases showed post-treatment angiographic aneurysm recurrence. Both cases were managed with repeat coiling and overlapping stent placement. Endovascular management using single/overlapping stent and if possible coil placement is technically safe and feasible in blister aneurysms. Overlapping stents lead to better aneurysm occlusion than a single stent. Blister aneurysm in dorso-medial ICA showed higher tendency of continued growth/recurrence, higher incidence of clinical vasospasm and in these cases early angiographic follow-up is advisable. Repeat treatment should be considered promptly if necessary.

Impedance-Matched Wireless Power Transfer Systems Using an Arbitrary Number of Coils With Flexible Coil Positioning

This letter presents a new analytic design method for impedance-matched wireless power transfer (WPT) systems using an arbitrary number of coils. For deriving the impedance matching condition, we have used an equivalent circuit of the WPT system. It allows us to avoid solving voltage-current equations for the actual circuit. For verifying the proposed design method, an impedance-matched WPT system with one repeater coil has been designed and fabricated. This letter also shows that the distances between the coils can be varied maintaining the impedance-matching performance, and the distances can be determined analytically using the presented design method. Application of the presented design method can be found in designing WPT systems that require flexible coil positioning.

Time-resolved Magnetic Resonance Angiography for assessment of recanalization after coil embolization of visceral artery aneurysms

SummaryBackground:Follow-up imaging after coil embolization of visceral artery aneurysms is important for detecting recanalization. However, CT examination is susceptible to coil artifacts, which sometimes makes it difficult to assess recanalization. We report 2 cases where recanalization was successfully visualized using time-resolved magnetic resonance angiography after coil embolization of visceral artery aneurysms (one case of right internal iliac artery aneurysm and one case of splenic artery aneurysm). Repeat coil embolization was successfully performed.Case Report:Case 1. An 80-year-old male patient with right internal iliac artery (IIA) aneurysm underwent coil embolization. Aneurysm was located at the bifurcation of the right IIA and therefore, after making a femorofemoral bypass, the distal part of the right IIA, aneurysm and the common iliac artery were embolized with a coil. One year later, the size of the aneurysm seemed to have increased on CT. However, the details were not determined because of metal artifacts. Thus, time-resolved MRA was performed and showed minute vascular flow inside the aneurysm. Angiography was subsequently performed and blood flow inside the aneurysm was visualized similar to the findings in time-resolved MRA. Coil embolization was performed once more and vascular flow inside the aneurysm disappeared. Case 2. A 36-year-old male patient with a splenic artery aneurysm underwent coil packing with preservation of splenic artery patency. Four years later, coil compaction was suspected in a CT scan, but CT could not evaluate recanalization because of severe metal artifacts. Angiography was subsequently performed, showing recanalization of the aneurysm as did the time-resolved MRA. Therefore, coil embolization of the aneurysm and splenic artery was performed again.Conclusions:Follow-up imaging after coil embolization of visceral artery aneurysms is important for detecting recanalization. However, it is sometimes difficult to assess recanalization with CT because of artifacts caused by metal. In our cases, recanalization of aneurysms was clearly shown by time-resolved MRA and re-embolization was successfully performed.In conclusion, time-resolved MRA appears to be useful in assessment of recanalization of visceral artery aneurysms after coil embolization.

Positioning-Free Resonant Wireless Power Transmission Sheet With Staggered Repeater Coil Array (SRCA)

A magnetically resonant wireless power transmission sheet (WPTS) on a printed circuit board is developed. WPTS wirelessly supplies the power to electronic devices including the wearable wireless healthcare devices anywhere on the sheet with high efficiency. In order to increase a power transmission efficiency degraded by a misalignment of a receiver coil, a transmitter coil array and a proposed staggered repeater coil array (SRCA) are stacked in WPTS. One transmitter coil closest to the receiver coil and the surrounding four repeater coils are selectively activated based on the result of a position detection of the receiver coil. By adding SRCA to the transmitter coil array, the measured power transmission efficiency at the worst-case misalignment increases from 4.8% to 64% at a distance of 15 mm between the transmitter and receiver coils with a diameter of 40 mm. The measured results are verified by electromagnetic simulations.

Cortical Blindness, Transient and Otherwise, Associated with Detachable Coil Embolization of Intracranial Aneurysms

Cortical visual loss is a rare complication of cerebral angiography without a definitive pathophysiology. Given the rapid increase in endovascular procedures used to treat cerebral aneurysms, we explored the prevalence of this complication and whether we could add to the understanding of this disorder. We performed a retrospective review of all procedures performed with the same contrast agent and detachable coils for treatment of posterior circulation aneurysms by 1 endovascular surgery service from 1996 to 2006. All patients were evaluated before and after each procedure by a team that included a neuro-ophthalmologist. Of 137 intra-arterial treatment procedures performed for posterior circulation aneurysms, we identified 4 patients with cerebral vision loss complications. During the same time period, >500 aneurysms of the anterior cerebral circulation were treated without this complication. The visual field loss was unilateral in 2 and bilateral in 2 patients. Recovery was complete in 3 and almost normal in the fourth patient. The amount of contrast used and the duration of the procedure were similar among all patients. The 4 patients had no identified specific risk factors for developing procedure-associated occipital dysfunction, all 4 had undergone prior angiography, and 1 patient had undergone repeat coiling, without complication. The 2.9% prevalence of cerebral visual loss with endovascular coil treatment of posterior circulation aneurysms is higher than that for angiography alone. Our patients recovered well with corticosteroid and intravenous hydration treatment. Recognizing the self-limiting nature of this problem might prevent an unneeded intervention.

Report Coiling for Coiled Cerebral Aneurysm with Rapid Recurrence and Bleeding: Report of a Case

Spontaneous subarachnoid hemorrhage (SAH) is a common presentation in an emergency department and most often results from a ruptured cerebral aneurysm. Traditionally, the aneurysm was managed with microsurgical clipping via open craniotomy. With advances in endovascular technology, many patients have been treated worldwide with coil embolization in the recent decade. Nevertheless, its longterm efficacy is still under investigation. Some patients will experience the problem of regrowth or recanalization of aneurysms. We report hereby a 47-year-old man with an anterior communicating artery (ACOM) aneurysm which was treated by endovascular coiling primarily. The aneurysm regrew rapidly later in another direction, however, and ruptured within 2 months. A second endovascular approach with coiling secured the recurrent aneurysm again smoothly. Upon further angiographic follow-up 3 months later, recanalization of the aneurysm after the second coiling occured. Repeat coiling was performed to embolize the aneurysm successfully. Remarkably, post-coiling headache developed after the third coiling procedure, but no evidence of rebleeding or rupture event was detected in a followup study. Conservative treatment with osmotic diuretic was given for one week and he recovered well. We have reviewed the relevant literature and present clinical features, risk factors, pathogenesis and the feasible management of repeat coiling.

Management of aneurysms involving branches of the celiac and superior mesenteric arteries: A comparison of surgical and endovascular therapy

Aneurysms involving branches of the superior mesenteric and celiac arteries are uncommon and require proper management to prevent rupture and death. This study compares surgical and endovascular treatment of these aneurysms and analyzes outcome. Patients at the Mount Sinai Medical Center in New York who were treated for aneurysms in the branches of the celiac artery and superior mesenteric artery were identified through a search of the institution's medical records and endovascular database. Patient demographics, history, clinical presentation, aneurysm characteristics, treatments, and follow-up outcome were retrospectively recorded. Significant differences between patients treated by surgical or endovascular therapy were determined by using Student's t test and chi2 analysis. Between January 1, 1991, and July 1, 2005, 59 patients with 61 aneurysms were treated at a single institution. Twenty-four patients had surgical repair, and 35 underwent endovascular treatment, which included coil embolization and stent-graft therapy. Splenic (28) and hepatic (22) artery aneurysms predominated. Eighty-nine percent of splenic artery aneurysms were true aneurysms and were treated by endovascular and surgical procedures in near equal numbers (14 and 11, respectively). Pseudoaneurysms were significantly more likely to be treated by endovascular means (P < .01). The technical success rate of endovascular treatment for aneurysms was 89%, and failures were successfully treated by repeat coil embolization in all patients who presented for retreatment. Patients treated by endovascular techniques had a significantly higher incidence of malignancy than patients treated with open surgical techniques (P = .03). Furthermore, patients treated by endovascular means had a shorter in-hospital length of stay (2.4 vs 6.6 days, P < .001). Endovascular management of visceral aneurysms is an effective means of treating aneurysms involving branches of the celiac and superior mesenteric arteries and is particularly useful in patients with comorbidities, including cancer. It is associated with a decreased length of stay in the elective setting, and failure of primary treatment can often be successfully managed percutaneously.

Verlaufsbeschreibung eines teilthrombosierten symptomatischen Basilariskopfaneurysmas mit teilweiser Rekanalisierung nach Coiling

A 72-year-old patient was referred to the neuroradiological department for diagnostic angiography. She was suffering from vertigo and double vision. Magnetic resonance imaging performed elsewhere had demonstrated a giant aneurysm of the basilar artery tip 2 cm in diameter. Angiography revealed a large aneurysm with a broad neck that was partially thrombosed, which precluded closure by coiling. Neurosurgical management by clipping also appeared to be unsuitable because of the proximity to the cerebrum. The decision was reached to proceed expectantly by closely monitoring the clinical course. When the aneurysm increased in size in the ensuing weeks, coiling was performed successfully. Angiographic follow-up showed reperfusion of the aneurysm neck and closure was again achieved by repeat coiling. Reperfusion is not a rare complication following coiling and often necessitates renewed intervention.

Repeat Endovascular Treatment in Post-Embolization Recurrent Intracranial Aneurysms

The purpose of this study was to describe clinical situations requiring repeat embolization in patients previously treated by endovascular coil embolization for intracranial aneurysms, and to report on our experiences of repeat embolization (RE). A total of 466 patients harboring 522 intracranial aneurysms were treated by endovascular coil embolization at our institution during the period between December 1992 and August 2004. We studied 32 patients who underwent repeat coil embolization (RE) owing to recanalization or aneurysm recurrence. Radiological and clinical data were reviewed to determine the reasons, results, and technical problems of RE. Thirty-nine sessions of RE were performed in 32 patients; four patients underwent RE twice and another patient three times. The major reason for RE was asymptomatic aneurysmal recanalization owing to coil compaction and/or loosening. The time interval between RE and the previous embolization was 12 months or less in 27 sessions. Complete or near complete occlusion of the aneurysm was achieved in all cases without procedure-related morbidity or mortality. Radiolucent gaps between the coil masses were observed in 17 cases. RE is a safe and effective treatment option in cases of recanalized or recurrent aneurysms. Close follow-up evaluation is essential in patients with intracranial aneurysms after coil embolization.