Radiofrequency Generator Research Articles

Experimental study on diluted hydrochloric acid enlarging radiofrequency ablation lesions in excised porcine livers

This study evaluated the influence of continuous infusion of diluted hydrochloric acid during radiofrequency ablation (RFA) on the size of ablated lesions. Experiments were performed in 20 excised porcine livers using three different treatment modalities: (1) normal saline-enhanced RFA (NS-RFA), which was normal saline pumped into ablated tissue during RFA; (2) diluted hydrochloric acid ablation (DHAA), which was 3 mol/L diluted hydrochloric acid (HCl) injected into hepatic tissue without RFA; and (3) HCl-enhanced RFA (HCl-RFA), which was 3 mol/L diluted HCl continuously infused into ablated tissue during RFA. We produced 20 HCl-RFA and NS-RFA lesions, respectively, using a monopolar perfusion electrode connected to a commercially available radiofrequency generator, and 20 DHAA lesions using an 18-gauge Chiba needle. The ablated lesions were evaluated both macroscopically and histologically. Dimensions of lesions were compared among HCl-RFA, NS-RFA, and DHAA. The ablated lesions had an elliptical-like shape and were well-demarcated with normal liver tissue. The mean volume, longitudinal diameter, and transverse diameter of NS-RFA lesions were 11.24±0.29 cm(3), 3.4±0.07 cm, and 2.48±0.03 cm, those of HCl-RFA lesions were 58.14±3.05 cm(3), 5.51±0.05 cm, and 4.49±0.11 cm, and those of DHAA lesions were 4.41±0.16 cm(3), 2.43±0.08 cm, and 1.8±0.03 cm, respectively. The mean dimensions of HCl-RFA lesions were the largest among the three types of ablation (P < 0.001). Under the present experimental conditions, the continuous infusion of diluted HCl during RFA can generate larger ablated lesions than NS-RFA or DHAA in excised porcine livers.

High-power calibration and measurement method for bio-electromagnetic study

A novel method for high-power calibration/measurement is presented in this work. This method employs a coupler and a dipole antenna to achieve high-power measurement. The coupler serves as a low-power sensor, whereas the dipole antenna is responsible for the high-power measurement. This method successfully calibrated a 600 W 13.56 MHz radio frequency generator and is potentially useful for even higher power measurement, as well as for hazardous high-intensity electromagnetic environment measurement, avoiding the use of expensive high-power metres.

Effective Treatment of Atrophic and Icepick Acne Scars Using Deep Non-Ablative Radiofrequency and Multisource Fractional RF Skin Resurfacing

Background and Objectives: Effective treatment for atrophic (depressed) and icepick acne scars requires treatment of both epidermis—for roughness, texture and hyperpigmentation, and the dermis—for collagen remodeling. All first generation radiofrequency systems allow nonablative RF treatment while a few others allow simple bipolar Fractional RF skin resurfacing. The FDA cleared multisource radiofrequency therapy system (EndyMed PRO, EndyMed Ltd., Cesarea, Israel) allows, for the first time, phase controlled multisource RF for both deep (up to 11 mm) non ablative RF and fractional RF skin resurfacing on the same treatment device. Study Design/Materials and Methods: Ten subjects with atrophic acne scars were enrolled in the study. Patients were photographed using standardized methods. In each treatment session, each patient received a full face 3DEEP non ablative skin tightening treatment followed by a Fractional skin resurfacing treatment. The treatment sessions were repeated once a month to a total of up to 4 treatments. Results: All subjects experienced mild-moderate edema and erythema as an immediate response to treatment. Edema resolved after up to three hours post treatment and erythema lasted up to 2 days. Micro ablative crusts were formed 1 - 2 days post treatments and lasted up to 5 days on facial areas. Patients' photographs—before each treatment session and 1 and 3 months after the last session—were graded according to the accepted Cosmetic Improvement Scale. All patients obtained significant skin improvement. Seventy percent of patients had 50% - 75% improvement one month after the third treatment session while the other thirty percent experienced a 25% - 50%. Discussion and Conclusions: The presented results describe for the first time a new treatment system (EndyMed PROTM) that allows both deep non ablative RF delivery and Fractional skin resurfacing on the same treatment platform. This work shows the synergy of combining these two applications for the improvement of acne scars, as well as for some secondary possible pigmentation and vascular improvement.

Bonding and impedance matching of acoustic transducers using silver epoxy

Silver epoxy was selected to bond transducer plates on glass substrates. The properties and thickness of the bonding medium affect the electrical input impedance of the transducer. Thus, the thickness of the silver epoxy bonding layer was used as a design parameter to optimize the structure for the transducer input impedance to match the 50Ω output impedance of most radio frequency (RF) generators. Simulation and experimental results show that nearly perfect matching is achieved without using any matching circuit. At the matching condition, the transducer operates at a frequency band a little bit below the half-wavelength resonant frequency of the piezoelectric plate. In experiments, lead titanate (PT) piezoelectric plates were employed. Both full-size, 11.5mm×2mm×0.4mm, and half-size, 5.75mm×2mm×0.4mm, can be well matched using optimal silver epoxy thickness. The transducer assemblies demonstrate high efficiency. The conversion loss from electrical power to acoustic power in soda-lime glass is 4.3dB. This loss is low considering the fact that the transducers operate at off-resonance by 12%. With proper choice of silver epoxy thickness, the transducer can be matched at the fundamental, the 3rd and 5th harmonic frequencies. This leads to the possible realization of triple-band transducers. Reliability was assessed with thermal cycling test according to Telcordia GR-468-Core recommendation. Of the 30 transducer assemblies tested, none broke until 2900 cycles and 27 have sustained beyond 4050 cycles.

Radiofrequency-Assisted Liver Resection With a Comb-Shaped Bipolar Device Versus Clamp Crushing

In liver surgery, clamp-crushing (CC) procedure has been shown to be the most efficient system for liver transection. Recently, it has been suggested that radiofrequency-assisted liver resection (RFALR) may be more advantageous, but sufficient evidence has yet to be accumulated. The control group was constituted by 32 patients undergoing CC liver transection. The study group included 13 patients undergoing RFALR with a new fully automated radiofrequency generator supplying a comb-shaped bipolar multielectrode device. RFALR allowed a faster hepatic transection and reduced both surgical time and intraoperative blood loss. RFALR was the only independent prognostic indicator of bleeding during liver transection. No significant liver damage and postoperative complications, particularly biliary leakage and stenosis, were experienced in the RFALR group. Compared with the CC procedure, this bipolar device was shown to be safe and effective in liver resections, allowing a very clean surgical field without increase of postoperative complications.

Gyrotron and its Electron Beam Source: A Review

Microwave occupies a glorious position in the electromagnetic spectrum and in that there are a number of devices in this frequency regime which are capable of high power operations. Among them, gyrotron has proven to be an efficient source for radio frequency (RF) generation at high power level and up to very high frequency. The gyrotron consists of several components like electron beam source, interaction structure, quasi-optical launcher, collector, RF window, magnet system, etc. All the components have their distinct role in the function of the device. Among them, electron beam source also called magnetron injection gun (MIG) is the generator of electron beam and it is very essential that MIG should produce and provide electron beam suitable for the beam-wave interaction at the interaction structure for the effective power growth. The paper presents the introduction of a microwave tube, gyrotron and its components alongwith review of the previous work, the background and the applications. The functions of various components of a gyrotron are discussed with particular highlighting on the electron beam emission from the electron beam source and the beam-wave interaction for power growth in the device. A review on different types of gyrotron electron beam sources is also presented.

Renal Denervation Revisited: Promising Treatment for Resistant Hypertension?

Renal sympathectomy has been in use since the 1930s to reduce blood pressure (BP) in patients with severe hypertension. Radical surgical sympathectomy and therapeutic splanchnicectomy were used before the advent of modern pharmacologic treatments to treat severe hypertension but these methods were largely abandoned with the availability of newer antihypertensive drugs that were both effective and had minimal side effects in the mid-late 1960s. Despite these newer efficacious drugs there remain patients with severe resistant hypertension. Renal sympathetic nerves contribute to the development and perpetuation of hypertension, and sympathetic outflow to the kidneys is activated in patients with essential hypertension. Efferent sympathetic outflow stimulates renin release, increases tubular sodium reabsorption, and reduces renal blood flow. Afferent signals from the kidney modulate central sympathetic outflow and thereby directly contribute to neurogenic hypertension. This was the basis for the use of nonselective surgical sympathectomy in the past. There has been a recent reemergence of interest in ablation of the renal sympathetic nerves using a catheter-based approach. A newly developed endovascular catheter technology enables selective denervation of the human kidney, with radiofrequency (RF) energy delivered in the renal artery lumen, accessing the renal nerves located in the adventitia of the renal arteries. This percutaneous, catheter-based approach is applied to selectively ablate the renal sympathetic nerves. In this approach, ablation is achieved percutaneously via the lumen of the main renal artery using a catheter connected to an RF generator. After gaining access via the femoral artery and confirmation of anatomic eligibility with renal angiography, the treatment catheter (Simplicity; Medtronic, Inc, Mountain View, CA) is introduced into each renal artery, and discrete RF ablations lasting 2 minutes each are applied to achieve 6 ablations separated both longitudinally and rotationally within each renal artery. Catheter tip temperature and impedance are constantly monitored during ablation, and RF energy delivery is regulated according to a predetermined algorithm. The mean duration of the procedure is less than 40 minutes. Patients often report back pain during the procedure so conscious sedation and narcotics are generally used. Complications have been infrequent and fairly minor but do include pseudoaneurysms at the puncture site and rarely renal artery dissection, which has been managed by stenting. An initial study of this approach showed successful renal denervation with both reductions of sympathetic activity and renin release in conjunction with reductions of central sympathetic outflow. This study showed substantial reductions of BP without substantial procedure-related complications. A larger study (Renal Denervation in Patients With Uncontrolled Hypertension [Symplicity 2]) was then performed using this RF catheter ablation procedure in a randomized trial of 106 patients with resistant hypertension despite treatment with an average of 5 antihypertensive medications including a diuretic. The patients were evaluated at 6 months. RF ablation significantly decreased the office BP from 178 ⁄97 mm Hg to 143 ⁄85 mm Hg compared with no decrease in BP in patients who were maintained on baseline antihypertensive therapy. A systolic BP <140 mm Hg was attained significantly more often with RF ablation (19% vs 4%). There was no significant difference between the groups in kidney function. Complications related to RF ablation included one femoral artery pseudoaneurysm. Long-term data regarding efficacy and safety of this procedure are limited. In a cohort study of 153 patients with resistant hypertension treated with catheter-based RF ablation, medical evaluation was performed in 64 patients at 12 months and 18 patients at 24 months. Compared with baseline, BP was reduced by 23 ⁄11 mm Hg at 12 months and 32 ⁄14 mm Hg at 24 months. The average number of antihypertensive medications used was the same at last follow-up as it was at baseline. Renal artery stenosis was diagnosed and stented in 1 patient 6 months after RF ablation. Another recent substudy assessed the effects of renal sympathetic denervation by RF ablation on BP reduction and sleep apnea severity in 10 patients with severe hypertension and sleep apnea. Antihypertensives were not changed during the study. Three and 6 months after renal denervation, in-office systolic BP and diastolic BP were decreased by 34 ⁄13 mm Hg. Significant decreases were also observed in plasma glucose concentration, glycated hemoglobin levels, and a decrease in apnea-hypopnea index at 6 months after renal denervation. This catheter-based approach to renal denervation presents a novel approach to severe resistant hypertension. Renal denervation has the potential to improve BP control most likely via interference with both From the Department of Medicine, Renal Division, Hypertension Program, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA Address for correspondence: Debbie L. Cohen, MD, Renal Division, Perelman School of Medicine at the University of Pennsylvania, 1 Founders Building, 3400 Spruce Street, Philadelphia, PA 19104 E-mail: debbie.cohen@uphs.upenn.edu DOI: 10.1111/j.1751-7176.2011.00563.x

Abstract 17060: Incidence of Tissue Coring during Transseptal Catheterization When Using Electrocautery and a Standard Transseptal Needle

Introduction. The application of radiofrequency (RF) electrocautery to a standard, open-ended transseptal needle has been used to facilitate transseptal puncture (TSP). The purpose of this study was to determine the incidence of cardiac tissue coring when this technique is used. Methods. A model using excised swine hearts submerged in a saline-filled basin was developed to simulate TSP with electrocautery and a standard transseptal needle. Four types of adult Brockenbrough needles and two different size swine hearts were used. Punctures were performed without the use of electrocautery, and by delivering RF energy to the transseptal needle using a standard Bovie electrocautery pen and an RF generator set to 10W and 15W, in both “pure” and “blend” cut settings, at three target sites (Fossa Ovalis [FO], non-Fossa Ovalis septum [Non-FO], and Aortic [AO]). The tissue of the submerged heart was gently tented, and the needle was advanced on delivery of RF. The devices were retracted, and the needle was flushed in a collection basin. The basin was inspected for tissue. Results. See Figure. None of the TSPs without cautery caused tissue coring. For TSP's using electrocautery, the frequency of coring was at least 21% for any puncture permutation used in the study, and averaged 37% at septal sites (p &lt; 0.05 compared to punctures without cautery). Tissue coring occurred in 33/96 (35%) punctures through the FO, and 38/96 (40%) punctures through non-FO septum (Figure 3a). The frequency of tissue coring at aortic sites was 62/96 (65%), which was significantly higher than at the septal sites (p&lt;0.001). Conclusions. In an animal preparation, TSP at the level of the fossa ovalis using electrocautery and a standard open-ended Brockenbrough needle resulted in coring of the septal tissue in one third of cases. These results raise concern about the risk of systemic embolism of cardiac tissue when this technique is used in humans.

Influence of radical power on the electrical and optical properties of ZnO:N films grown by metal-organic chemical vapor deposition with N2O plasma doping source

N-doped ZnO (ZnO:N) films are grown by a low-pressure plasma assisted metal-organic chemical vapor deposition system on insulating Si (111) substrate. N2O plasma is used as the N precursor of ZnO:N films, which is activated by a radio frequency generator. The influence of activating power on the properties of ZnO films is studied by means of X-ray diffraction, Hall effect, X-ray photoelectron spectroscopy and low temperature photoluminescence measurements. P-type ZnO:N films with acceptable electrical and optical properties are achieved under the optimal activating power conditions. XPS study reveals a competition between acceptor NO and donor (N2)O during doping influence the properties of ZnO films.

Permanent-Magnet Helicon Discharge Array

Industrial applications of plasmas often require uniform coverage of large areas, such as in plasma coatings, display panels, and semiconductor wafers. A single source would have to be very large, but an array of small sources can be much more compact and yet cover an arbitrarily large area. Such sources can be inductively coupled plasmas (ICPs) which are powered by radio-frequency generators. Helicon-wave sources have been found to create higher plasma densities than ICPs at the same power, but these require a dc magnetic field, which normally would entail large and heavy electromagnets and their dc power supplies. Annular permanent magnets can produce helicon plasmas if used in the innovative way described here. An eight-tube array of such sources has been built and tested.

High-Density Blue-Mode Argon Plasma Under an Expanding Magnetic Field Provided by Permanent Magnets

A 13-cm-diameter magnetically expanding plasma source using only permanent magnets and a high-power radio frequency (RF) generator of 13.56 MHz are installed in the Large diameter Permanent Magnets expanding Plasma machine at I wate University. The source is preliminarily operated for 500-W and 3-kW RF powers of 13.56 MHz in argon of 0.2 Pa. The double concentric arrays of the permanent magnets can provide expanding magnetic fields of about 80 G in the source tube and about 10 G at 30 cm downstream of the source exit. A purple light emission is seen for low-power condition of 500 W, while a blue-mode argon plasma is observed for high-power operation of 3 kW. The blue light emission implies the production of the high-density plasma by helicon mode discharge. In this paper, the images of the plasmas are presented.

La dénervation rénale un traitement pour l’hypertension artérielle résistante

Arterial hypertension is a major healthcare issue affecting between 30 and 40% of the adult population in industrialized countries. Despite the availability of numerous pharmaceutical treatments, arterial hypertension often remains uncontrolled. A non-negligible percentage of patients are refractory to multiple-drug therapy, which exposes them to an increased risk of cardiovascular events. Percutaneous, renal denervation using a catheter connected to a low energy radiofrequency generator has proven effective in decreasing arterial pressure in patients resistant to medical therapy, by reducing afferent nerve activity. In order to be eligible for this therapeutic approach, patients must have uncontrolled essential hypertension despite treatment with a combination of three anti-hypertensive drugs including a diuretic agent, and ≥ 45 mL/min glomerular filtration rate. The initial registry study demonstrated that catheter-based sympathetic renal denervation was a simple and safe procedure resulting in a significant and durable reduction in arterial pressure. Subsequently, a randomized controlled trial (the Symplicity HTN-2 trial) showed a mean 32/12 mmHg decrease in blood pressure measurements in the group of patients who underwent renal denervation whereas no difference was observed in the control group. The reduction in blood pressure was still present at 24-month follow-up. No procedure-related complications were reported and no instances of renal artery stenosis or aneurysmal dilatation were evidenced during the follow-up period. No cases of renal function impairment or deterioration were recorded. This technique seems to be a promising strategy in patients suffering from this serious condition. In order to demonstrate the actual benefit of this technique, we report the case of two patients who underwent renal denervation in our institution.

270 Short-term results of pulmonary vein isolation for paroxysmal atrial fibrillation using duty-cycled bipolar and unipolar radiofrequency energy: The initial Québec experience

BackgroundElectrical isolation of pulmonary veins (PV) is key to long term success of paroxysmal atrial fibrillation (AF) ablation. PV antral isolation using a conventional irrigated-tip catheter is often technically challenging and time consuming.MethodsTwenty-nine patients (mean age 55+/−13 years, 69% males) with symptomatic paroxysmal AF refractory to antiarrhythmic drugs underwent ablation with a circular mapping/ablation decapolar catheter (PVAC). Ablation was performed in the antral region of PVs with a power-modulated bipolar/unipolar radiofrequency (RF) generator using 8W delivered simultaneously through 2-10 electrodes, as selected by the operator. All ablations were performed under general anesthesia.ResultsMean left ventricular ejection fraction was 60+/−4% and mean left atrial volume was 27+/−5 ml/m2. Overall, 114 of 116 targeted PVs (98%) were isolated with the PVAC system with a mean of 32+/−8 RF applications per patient (total RF time 1921+/−493 seconds): 9+/−3 in the right superior PV, 7+/−3 in the right inferior PV, 9+/−4 in the left superior PV, and 7+/−3 in the left inferior PV. The mean procedure and fluoroscopy times were 171+/−35 min and 34+/−12 min respectively. The mean activated clotting time was 335+/−27 sec. After a mean follow-up of 3.6+/−1.7 months, 21 patients (72%) were free of AF without antiarrhythmic drugs . No procedure-related complications were observed.ConclusionPV isolation can be performed effectively, timely and safely using a circular decapolar ablation catheter. Long term and randomized data are needed to compare all different tools and ablation strategies for AF. BackgroundElectrical isolation of pulmonary veins (PV) is key to long term success of paroxysmal atrial fibrillation (AF) ablation. PV antral isolation using a conventional irrigated-tip catheter is often technically challenging and time consuming. Electrical isolation of pulmonary veins (PV) is key to long term success of paroxysmal atrial fibrillation (AF) ablation. PV antral isolation using a conventional irrigated-tip catheter is often technically challenging and time consuming. MethodsTwenty-nine patients (mean age 55+/−13 years, 69% males) with symptomatic paroxysmal AF refractory to antiarrhythmic drugs underwent ablation with a circular mapping/ablation decapolar catheter (PVAC). Ablation was performed in the antral region of PVs with a power-modulated bipolar/unipolar radiofrequency (RF) generator using 8W delivered simultaneously through 2-10 electrodes, as selected by the operator. All ablations were performed under general anesthesia. Twenty-nine patients (mean age 55+/−13 years, 69% males) with symptomatic paroxysmal AF refractory to antiarrhythmic drugs underwent ablation with a circular mapping/ablation decapolar catheter (PVAC). Ablation was performed in the antral region of PVs with a power-modulated bipolar/unipolar radiofrequency (RF) generator using 8W delivered simultaneously through 2-10 electrodes, as selected by the operator. All ablations were performed under general anesthesia. ResultsMean left ventricular ejection fraction was 60+/−4% and mean left atrial volume was 27+/−5 ml/m2. Overall, 114 of 116 targeted PVs (98%) were isolated with the PVAC system with a mean of 32+/−8 RF applications per patient (total RF time 1921+/−493 seconds): 9+/−3 in the right superior PV, 7+/−3 in the right inferior PV, 9+/−4 in the left superior PV, and 7+/−3 in the left inferior PV. The mean procedure and fluoroscopy times were 171+/−35 min and 34+/−12 min respectively. The mean activated clotting time was 335+/−27 sec. After a mean follow-up of 3.6+/−1.7 months, 21 patients (72%) were free of AF without antiarrhythmic drugs . No procedure-related complications were observed. Mean left ventricular ejection fraction was 60+/−4% and mean left atrial volume was 27+/−5 ml/m2. Overall, 114 of 116 targeted PVs (98%) were isolated with the PVAC system with a mean of 32+/−8 RF applications per patient (total RF time 1921+/−493 seconds): 9+/−3 in the right superior PV, 7+/−3 in the right inferior PV, 9+/−4 in the left superior PV, and 7+/−3 in the left inferior PV. The mean procedure and fluoroscopy times were 171+/−35 min and 34+/−12 min respectively. The mean activated clotting time was 335+/−27 sec. After a mean follow-up of 3.6+/−1.7 months, 21 patients (72%) were free of AF without antiarrhythmic drugs . No procedure-related complications were observed. ConclusionPV isolation can be performed effectively, timely and safely using a circular decapolar ablation catheter. Long term and randomized data are needed to compare all different tools and ablation strategies for AF. PV isolation can be performed effectively, timely and safely using a circular decapolar ablation catheter. Long term and randomized data are needed to compare all different tools and ablation strategies for AF.

Destruction of methane in low-pressure, electrodeless radio frequency plasma on quartz walls

The destruction of methane in a low pressure, electrodeless radiofrequency discharge was studied by mass spectrometry. Plasmas were created in a quartz tube with the inner diameter of 3.6 cm. A coil with 6 turns was fixed onto the tube and connected to radio frequency (RF) generator via a matching network. Methane flows between 1.16 and 3.30 mbar.l/s and various RF powers up to 1200 W were used. Depending on gas flow and RF power, the discharge was either in E or H mode. The evolution of different hydrocarbon species versus discharge power was measured systematically by a differentially pumped mass spectrometer. No carbon deposit on the quartz walls was seen during the scans. The results showed that the destruction of methane depended on the flow rate as well as the discharge power and was accomplished already in the E mode. Well-pronounced maxima in the formation of both ethane and acetylene were observed at low gas flow rates. The observed products from radical recombination evolved with plasma conditions, and their contribution to the global carbon balance strongly decreased at high power-per-particle density. The functionality of secondary hydrocarbon formation with respect to the experimental parameters has been analyzed and a simple kinetic model is proposed in order to account for the observed trends.

Single-cycle radio-frequency pulse generation by an optoelectronic oscillator

We demonstrate experimentally passive mode-locking of an optoelectronic oscillator which generates a single-cycle radio-frequency pulse train. The measured pulse to pulse jitter was less than 5 ppm of the round-trip duration. The pulse waveform was repeated each round-trip. This result indicates that the relative phase between the pulse envelope and the carrier wave is autonomously locked. The results demonstrate, for the first time, that single-cycle pulses can be directly generated by a passive mode-locked oscillator. The passive mode-locked optoelectronic oscillator is important for developing novel radars and radio-frequency pulsed sources and it enables studying directly the physics of single-cycle pulse generation.

Locoregional Control of Metastatic Well-Differentiated Thyroid Cancer by Ultrasound-Guided Radiofrequency Ablation

The purpose of this study was to evaluate the efficacy and safety of ultrasound-guided radiofrequency ablation (RFA) in the control of metastatic well-differentiated thyroid carcinoma in patients for whom surgery is not feasible. Between December 2004 and June 2008, 12 metastatic differentiated thyroid carcinomas (mean diameter, 13.8 mm; range, 4-28 mm) in 10 patients (six women, four men; mean age, 44.8 years) were treated with RFA. The inclusion criteria for RFA were fewer than three metastatic tumors confirmed with ultrasound-guided fine-needle aspiration biopsy, no metastatic tumor beyond the neck at RFA, and infeasibility of surgery. A radiofrequency generator and 18-gauge internally cooled electrodes with a 7-cm shaft length and 0.5- and 1-cm active tips were used depending on the size of the targeted tumors. Ten of the 12 metastatic tumors (83%) were treated in a single session of RFA, and the other two required two sessions. The ablation time ranged from 60 to 900 seconds. After treatment, the mean largest diameter decreased significantly from 13.8 ± 7.0 mm to 3.3 ± 3.9 mm (p = 0.002), as did mean volume, from 55.5 ± 50.3 mm(3) to 5.7 ± 9.3 mm(3) (p = 0.002). At the last follow-up evaluation, the serum thyroglobulin concentration had decreased in 7 of 10 patients. One patient had dysphonia immediately after RFA of a left surgical bed. Although surgery is the standard treatment of locally metastatic thyroid cancer, RFA is effective for locoregional control of metastatic well-differentiated thyroid carcinoma in patients for whom surgery is infeasible.

Treatment of persistent atrial fibrillation using phased radiofrequency ablation technology

A novel ablation system consisting of a duty-cycled phased radiofrequency generator and multielectrode mapping and ablation catheters has been introduced to provide ablation therapy in patients with symptomatic atrial fibrillation (AF). Contiguous lesions may be created using anatomically designed ablation catheters maneuvered under fluoroscopic guidance without the use of a 3D electroanatomic mapping system. In addition to pulmonary vein isolation using a circular, decapolar ablation catheter, an ablation strategy targeting complex fractionated atrial electrograms can be performed using two supplemental multiarray catheters specifically designed for ablation at the left atrial septum and within the left atrial body. Procedural times for treating persistent AF using phased radiofrequency are reported as being between 2 and 2.5 h. Freedom from AF ranges between 33 and 75% after a single procedure, which is comparable to other conventional ablation approaches (utilizing electroanatomic mapping). Additional studies in larger patient numbers are needed to understand the long-term maintenance of results and potential adverse effects of the technology.

Radiofrequency-Assisted Hepatic Resection

The only curative procedure to date for liver tumors is surgical resection, which remains a major procedure with marked morbidity and mortality. Radiofrequency (RF) has increasingly been used for both ablation and resection. On the basis of this technique, a new bipolar RF device, Habib 4X, has been developed and used clinically. We present our technique of liver resection with this device in a patient with colorectal liver metastases. A patient with situs inversus who had colorectal liver metastases in her left lobe underwent left lateral segmentectomy with the new device, a four-electrode bipolar resection device that uses RF energy for tissue necrosis. After laparotomy and intraoperative ultrasound, the plane resection was marked 1 cm away from the edge of the lesion. Coagulative desiccation was performed along this plane using this sealer connected to a RF generator. The necrosed band of parenchyma was then divided with a scalpel and resection completed. The length of the procedure was 105 minutes; resection time was 35 minutes. Total blood loss was 100 ml. No blood transfusions were required, and the patient was not admitted to the intensive care unit after surgery. The patient was discharged 10 days after surgery without any surgical complications. We think that RF-assisted liver resection with this new device is safe and effective. It is quicker than conventional RF and may reduce overall hospital stay in liver resection patients.

A Novel Experimental Animal Model of Arterial Stenosis Based on Endovascular Radiofrequency Energy Application

ABSTRACTPurpose: To develop a new rabbit model of arterial stenosis using endovascular radiofrequency (RF) energy. Materials and Methods: Ten rabbits were used for multiple endovascular RF applications to the aorta and left common carotid artery through the Habib™ VesCoag™ catheter. Angiography and color Doppler ultrasound were used to assess vessel patency immediately following the procedure and six weeks later. One rabbit was sacrificed following the procedure for histopathologic analysis of the vessel wall. Two rabbits died of aortic and carotid rupture, respectively, immediately after the procedure. The remaining seven rabbits were sacrificed after six-week follow-up for histopathological analysis. Results: Optimal RF generator settings to induce significant arterial stenosis (>50%) without complications were standardized at 24–26 watts (W) for 1.5 min for the aorta and 6 W for 1 min for the common carotid artery. The six-week follow-up showed permanent results in all surviving rabbits. Histopathology revealed intima and medial smooth muscle layer necrosis. Conclusion: We have developed a novel rabbit model of arterial stenosis using endovascular RF energy. Our model is fast, safe, inexpensive, and reproducible. It would be useful for experimental investigations and new therapeutic devices.

Generating Radiofrequency Ablation Lesions Using Magnetically Coupled Bipolar Catheters

Transmural lesions are difficult to produce in myocardial regions with thick walls, such as the left ventricle (LV), using conventional radiofrequency (RF) ablation catheters. This study was performed to evaluate the efficacy of magnetically coupled bipolar catheters and compare the performance with conventional unipolar and bipolar RF ablation catheters. Neodymium magnets assembled in ablation catheters were used to facilitate tissue contact in a bipolar RF ablation system. In vitro sheets of porcine skeletal muscle, with 10-mm thickness, were ablated with a 4-mm-tip unipolar RF ablation catheter (UA), a bipolar ablation system (BA) using a pair of 4-mm-tip catheters, and a magnetically coupled bipolar system (MB). The RF generator setting was 50 W and 90°C. RF energy was delivered for 30 or 60 seconds and five lesions were created in each ablation condition. The bottom side of the skeletal-muscle sheet was exposed to saline at 37°C and a flow of 5.6 L/min, mimicking the LV endocardial surface. The top side was exposed to air, mimicking the epicardial surface. In the 60-second ablation cases, the transmuralities were 0%, 0%, and 40% (UA, BA, and MB, respectively). The volumes of the lesions were 61.5 ± 8.5, 224.3 ± 51.8, and 359.3 ± 93.8 mm(3) (UA, BA, and MB, respectively). The magnetically coupled bipolar RF ablation system created transmural lesions more efficiently than the conventional ablation system, primarily due to higher RF current density and stronger tissue contact. This prototype method could be applied to the development of novel ablation devices for thick areas of tissue.