Radiofrequency Electrode Research Articles

可変型電極を用いた肝癌に対するラジオ波焼灼術の経験

可変型電極を用いた肝癌に対するラジオ波焼灼術の経験

Safety and Clinical Outcomes of Percutaneous Radiofrequency Ablation for Intermediate and Large Bone Tumors Using a Multiple-Electrode Switching System: A Phase II Clinical Study

PurposeTo evaluate the safety and clinical outcomes of radiofrequency (RF) ablation using a multiple-electrode switching system in patients with bone tumors > 3 cm. Materials and MethodsThis prospective study enrolled 20 subjects (15 men, 5 women; mean age 70.0 y ± 7.4 [SD]; range, 60–80 y) with malignant unresectable bone tumors. The maximum mean tumor diameter was 5.5 cm ± 2.0 (range, 3.1–10.0 cm). Two to three RF electrodes were placed into each bone tumor. Real-time CT fluoroscopic guidance was used with a multiple-electrode switching system. The primary endpoint was safety, as evaluated by Common Terminology Criteria for Adverse Events, until 12 months after bone RF ablation. As secondary endpoints, pain relief was evaluated by visual analog scale (VAS) scores before and 1 week after RF ablation; tumor response, by contrast-enhanced magnetic resonance imaging studies until 4 weeks after bone RF ablation; and survival, by Kaplan-Meier method. ResultsNo adverse event was found in 19 of 20 patients (95%). Grade 2 fever occurred in 1 patient (5%; 1/20). VAS scores decreased by ≥ 2 in 11 of 13 patients (84.6%) who had painful bone tumors. Tumor response (complete or partial response) was achieved in 16 of 18 patients (88.9%) who underwent follow-up imaging studies. The 1-year overall survival rate was 60.9%, and the median survival time was 14.1 months. ConclusionsBone RF ablation using this system is safe and achieves local tumor control and pain relief in patients with large bone tumors.

Real-time in vivo assessment of radiofrequency ablation of human colorectal liver metastases using diffuse reflectance spectroscopy

BackgroundThe success of radiofrequency (RF) ablation is limited by the inability to assess thermal tissue damage achieved during or immediately after the procedure. The goal of this proof-of-principle study was to investigate whether diffuse reflectance (DR) spectroscopy during and after RF ablation of liver tumours could aid in detecting complete tissue ablation. Material and methodsDR spectra were acquired in vivo in eight patients undergoing RF ablation for unresectable colorectal liver metastases, using a disposable spectroscopy needle. Intraoperative ultrasound imaging was used for accurate positioning of the RF electrode and the spectroscopy needle. Spectral changes were quantified and correlated to tissue histopathology and follow-up CT imaging. ResultsFor the lesions in which ablation was monitored by DR spectroscopy (N = 8), median tumour size was 1.6 cm (range 0.8–3.3 cm). We found an excellent correlation (97–99%) between thermal damage suggested by spectral changes and histology. DR spectroscopy allowed discrimination between non-ablated and ablated tissue, regardless whether the needle was placed in tumour tissue or in surrounding liver tissue. Additional measurements performed continuously during ablation confirmed that the magnitude of spectral change correlates with the histochemical degree of thermal damage. ConclusionsDiffuse reflectance spectroscopy allows accurate quantification of thermal tissue damage during and after RF ablation. Real-time feedback by DR spectroscopy could improve the accuracy and quality of the RF procedures by lowering incomplete ablation rates.

The Effectiveness of Multiple Electrode Radiofrequency Ablation in Patients with Hepatocellular Carcinoma with Lesions More than 3 cm in Size and Barcelona Clinic Liver Cancer Stage A to B2

Outcomes of hepatocellular carcinoma (HCC) lesions >3.0 cm in size including Barcelona Clinic Liver Cancer (BCLC) stage B after radiofrequency ablation (RFA) with a single electrode remain unsatisfactory. This study aimed to investigate the outcomes of RFA with multiple electrodes (ME-RFA) for HCC tumors 3.1-7.0 cm in size and BCLC stage B. This retrospective study included 70 consecutive patients with 58 medium- (3.1-5.0 cm) and 17 large- (5.1-7.0 cm) sized HCCs after ME-RFA using a controller. Outcomes in terms of complete response, primary technique effectiveness, local tumor progression, and overall survival were investigated. After 1-4 applications of ME-RFA, the rates of complete response and PTE in medium-sized tumors were 79.3% and 91.4%, respectively, and in large tumors were 76.5% and 94.1%, respectively. Overall, the major complication rate was 5.7%. After a median 21-month follow-up period, both two- and three-year estimated overall survival rates were above 80%. There were no significant differences in overall survival and local tumor progression rates between medium- and large-size tumors and among BCLC stages A, B1 and B2. A complete response to ME-RFA was the only significant factor associated with improved survival (p=0.008). In conclusion, ME-RFA can effectively treat 3.1-7.0-cm sized HCCs with a comparable outcome between medium- and large-size tumors and among BCLA stages A to B2.

Influence of layered skin structure on the distribution of radiofrequency currents in dermis and subcutaneous fat

The layered structure of skin with multiple interfaces separating the skin layers having very different electrical characteristics significantly modifies the spatial distribution of radiofrequency (RF) current in the skin compared to that in a homogeneous medium. In this study we present the analytical solutions of Laplace’s equation describing the current densities for a two-layer skin model with homogeneous single layers for the monopolar and bipolar configurations of RF electrodes. Then we analyze analytically and numerically the optimal distances between the RF electrodes providing the maximal current concentration in a given depth or in a given depths’ interval under the skin surface. It is demonstrated that two main parameters which significantly define the optimization condition are the thickness of the dermis and the reflection coefficient of the current at the dermis/subcutis interface. According to this model, under physiological conditions, the surface under RF electrode collecting 50% of the current entering subcutis is 184 times larger than in homogeneous medium. Such redistribution of RF current will significantly reduce the local density of the current entering the fat tissue reducing the effect of its selective heating.

Simulation and Visualization of Liver Cancer Ablation Focus in Optical Surgical Navigation

Radiofrequency ablation therapy of liver cancer is a local mini-invasive treatment technology with several advantages, such as low trauma, safety, effectiveness, and quick postoperative recovery. The application of the optical surgical navigation system in radiofrequency ablation therapy can realize the real-time positioning of surgical instruments and focus. The positioning results can be displayed on the computer, thereby guiding doctors to accurately insert the radiofrequency electrode into the focus and improving surgical efficiency. Meanwhile, the accurate evaluation of the form and size of the ablation focus by the navigation system is the key to realizing the complete ablation of liver cancer. Therefore, based on the heat conduction equation, this paper simplifies the simulation process of the ablation focus, calculates the volume of the ablation focus by distinguishing boundary points and internal points, achieves the effective simulation of the ablation results in the surgery, and reconstructs the ablation focus by using ray casting algorithm and mobile cube algorithm for 3D visualization processing, thereby providing doctors the convenience of being able to simulate the radiofrequency ablation surgery before the actual surgery.

TCT-764 Bipolar Radiofrequency Renal Denervation with the Vessix Catheter in Patients with Resistant Hypertension: 2-year Results from the REDUCE-HTN Trial

The Vessix Renal Denervation System (Boston Scientific, Marlborough, MA) consists of an over-the-wire low-pressure balloon catheter with an array of bipolar radiofrequency electrodes. Primary endpoint results of the REDUCE-HTN trial showed significant blood pressure reductions and a low major

Development of effective QCM biosensors by cyclopropylamine plasma polymerization and antibody immobilization using cross-linking reactions

Biosensors have been extensively developed and applied for biomedical and environmental studies. Although there are many different types of biosensing techniques, immobilization of the biorecognition biomolecules onto the sensor surface is always required. Cyclopropylamine pulsed plasma polymerization in radio frequency (RF) capacitive discharges was employed to deposit amine thin films on the gold electrode of quartz crystal microbalance (QCM) biosensors and the monoclonal antibody AL-01, specific to human serum albumin (HSA), was immobilized onto the plasma polymer surface. Two different amine plasma polymers were studied. They had a similar amount of primary amine groups, 1.3–1.5 at.%, as determined by chemical derivatization but their stability in water was different. The 1st type, deposited at the floating potential and 120 Pa, exhibited 16% thickness loss after 24 h in water whereas the 2nd type deposited at RF electrode and 50 Pa was completely stable (2% thickness loss). Glutaraldehyde (GA) coupling of AL-01 was employed for both types of the amine films and the performance of QCM immunosensors was evaluated by the immunoassay flow test. A high-stability of the frequency signal was obtained in both the cases but the 2nd type of the film provided low response to HSA. It was explained by its highly cross-linked structure and steric hindrance of active sites. Three different antibody immobilization methods were explored for the 1st type of the film. Stable baseline, selective and high response were recorded for GA and sulfo-SMCC methods. The results confirmed that the presented methodologies for the grafting of biomolecules on the gold are highly efficient and very promising for future use in biosensing.

Microendoscopy-guided percutaneous cordotomy for intractable pain: case series of 24 patients.

The aim of this study was to show that microendoscopic guidance using a double-channel technique could be safely applied during percutaneous cordotomy and provides clear real-time visualization of the spinal cord and surrounding structures during the entire procedure. Twenty-four adult patients with intractable cancer pain were treated by microendoscopic-guided percutaneous radiofrequency (RF) cordotomy using the double-channel technique under local anesthesia. A percutaneous lateral puncture was performed initially under fluoroscopy guidance to localize the target. When the subarachnoid space was reached by the guiding cannula, the endoscope was inserted for visualization of the spinal cord and surrounding structures. After target visualization, a second needle was inserted to guide the RF electrode. Cordotomy was performed by a standard RF method. The microendoscopic double-channel approach provided real-time visualization of the target in 91% of the cases. The other 9% of procedures were performed by the single-channel technique. Significant analgesia was achieved in over 90% of the cases. Two patients had transient ataxia that lasted for a few weeks until total recovery. The use of percutaneous microendoscopic cordotomy with the double-channel technique is useful for specific manipulations of the spinal cord. It provides real-time visualization of the RF probe, thereby adding a degree of safety to the procedure.

Bipolar radiofrequency ablation with 2 × 2 electrodes as a building block for matrix radiofrequency ablation: Ex vivo liver experiments and finite element method modelling

Purpose: Size and geometry of the ablation zone obtained by currently available radiofrequency (RF) electrodes is highly variable. Reliability might be improved by matrix radiofrequency ablation (MRFA), in which the whole tumour volume is contained within a cage of x × y parallel electrodes. The aim of this study was to optimise the smallest building block for matrix radiofrequency ablation: a recently developed bipolar 2 × 2 electrode system. Materials and methods: In ex vivo bovine liver, the parameters of the experimental set-up were changed one by one. In a second step, a finite element method (FEM) modelling of the experiment was performed to better understand the experimental findings. Results:The optimal power to obtain complete ablation in the shortest time was 50–60 W. Performing an ablation until impedance rise was superior to ablation for a fixed duration. Increasing electrode diameter improved completeness of ablation due to lower temperature along the electrodes. A chessboard pattern of electrode polarity was inferior to a row pattern due to an electric field void in between the electrodes. Variability of ablation size was limited. The FEM correctly simulated and explained the findings in ex vivo liver. Conclusions: These experiments and FEM modelling allowed a better insight in the factors influencing the ablation zone in a bipolar 2 × 2 electrode RF system. With optimal parameters, complete ablation was obtained quickly and with limited variability. This knowledge will be useful to build a larger system with x × y electrodes for MRFA.

Technical aspects of conventional and water-cooled monopolar lumbar radiofrequency rhizotomy

Radiofrequency ablation (RFA) is a safe and effective pain therapy with efficacy principally reliant upon induced thermal damage of neural sensory afferents. Most peripheral RFA involves induced axonal damage but cell bodies may be involved indirectly. Radiofrequency electrodes (RFE) are not simple high-temperature probes and better insight regarding RFE function from an electrical engineering viewpoint may improve clinical outcomes by reducing the risk of poor or inadequate heating of the target nerves. RFE heating is highly influenced by the configuration and properties of the perielectrode tissues with the shape and size of RFE-produced protein coagulum seen in vitro with homogeneous media such as egg white, liver, or chicken skeletal muscle undoubtedly significantly different than the biological lesions occurring during in vivo clinical use. Understanding RFA requires consideration of the nature of the specific perielectrode tissues. A theoretical basis for optimized RFE function for lumbar medial branch (MB) neurotomy is presented with introduction of the concepts of clinically useful heating and useless heating. Conventional RFE is limited in the amount of current/heating produced for a given active electrode surface area before producing a radiofrequency generator fault and an inverse relationship exists between clinically useful heating and useless heating. Technical details of RFE function are discussed that may differ from presently accepted technique. Tined RFE, similar in function to conventional RFE, may offer a small advantage if properly used, and possibly a disadvantage if used incorrectly. Directly conducted heat is often neglected in considering RFA, but should be considered, especially with water-cooled RFE (WCRFE). Theory and empirical results suggest that WCRFE might become a preferred tool for much, but not all, RFA, but adoption has been limited by electrode cost and reimbursement policies. Conventional and tined RFE may produce poor outcomes if placed improperly, but complications due to overheating are quite rare. Conversely, WCRFE introduces far more heat into perielectrode tissues and reduces the likelihood of a poor clinical outcome, but avoidance of complications due to overheating of adjacent tissues requires a thoughtful understanding of the spatial and thermal characteristics of the WCRFE.

Application of radiofrequency ablation for tongue venous malformation

To explore the therapeutic effect of radiofrequency ablation for tongue venous malformation( VM). From July 2013 to July 2014, 30 cases with tongue VM (local or diffuse) were retrospectively analyzed. 23 cases underwent radiofrequency ablation treatment. The radiofrequency electrode tip(0. 5 mm in diameter) was inserted into the lesion 1 mm below the bottom with 25 W in power and 15-30 s of pulse. The treatment was repeated when the electrode tip was removed back every 1 mm. Multi-point treatment was performed. 15 cases with unilateral VM were completely healed after one-stage radiofrequency ablation. 8 cases with bilateral VM received two-stage radiofrequency ablation with a 3-6 months of interval. Among the 8 cases, completely healing was achieved in 5 cases, partial VM residue happened in 3 cases due to its diffuse lesion and reservation of tongue function. 23 cases were followed up for 3 month to 1.5 years. Good cosmetic and functional results was achieved in 20 cases with no relapse. Partial VM residue was left in 3 cases. Radiofrequency ablation can effectively treat tongue VM with minimal morbidity and good cosmetic appearance. It also avoids the disadvantages of surgery.

Helical coil electrode radiofrequency ablation designed for application in osteolytic vertebral tumors—initial evaluation in a porcine model

Background contextRadiofrequency ablation (RFA) is emerging as a complementary treatment for vertebral metastases. Traditional RFA induces frictional heating leading to local tissue necrosis but often yields small, incomplete, and inhomogeneous zones of ablation in bone. We have developed a new bone-specific RFA electrode that uses a nontraditional frequency (27.12 MHz) and geometry (helical), exploiting a magnetic field and an electric field to generate larger and more comprehensive treatment zones. PurposeThe purpose of the study was to evaluate the feasibility and safety of the Bone Coil RFA electrode in the spine. Study designThis is a preclinical in vivo study based on basic science. MethodsUnder institutional approval, six healthy Yorkshire pigs received a sham and an RF treatment in two adjacent cervical vertebrae. To deploy the Bone Coil RFA device in dense porcine vertebrae, a surgical approach was required; an irrigated coring drill bit created a cylindrical path in the vertebral bodies through which the RFA electrodes were placed. The electronic circuit was completed by four grounding pads. Treatment was delivered for 10 minutes at 20 W (n=1), 25 W (n=1), and 30 W (n=4). To monitor the thermal rise and for safety, fiber-optic probes recorded temperatures in the center of each coil and near the spinal foramen. After the procedure, animals were monitored for 2 weeks. Magnetic resonance imaging (MRI) was completed immediately after treatment and at 14 days. Magnetic resonance image segmentation and histology were used to evaluate the ablation volume. ResultsComprehensive treatment of the porcine vertebrae was demonstrated by temperature monitoring, MRI, and histology. Large zones of RF ablation were obtained (RF: 3.72±0.73 cm3 vs. sham: 1.98±0.16 cm3, p<.05), confined within the vertebral body. Internal temperatures were elevated with RF (66.1°C–102.9°C), without temperature rise outside of the vertebrae (38.2°C±1.5°C). Mobility, neurological responses, and behavior were normal, consistent with preprocedural examination. Magnetic resonance imaging best visualized ablation at Day 14. Histology revealed comprehensive homogeneous coagulative necrosis with little peripheral sign of repair. ConclusionsThe Bone Coil RFA device created large intravertebral ablation volumes with no neurologic sequelae. Radiofrequency thermal ablation (clearly distinguished from the much smaller effects arising from core drilling) corresponded to the homogeneous necrosis visible on histology.

A Novel Electrode With Electromagnetic Tip Tracking in Ultrasonography-Guided Radiofrequency Ablation

The objective of this study was to compare the targeting and ablation performance between a newly developed radiofrequency (RF) electrode embedded with an electromagnetic position sensor (EMPS) at the electrode tip and a conventional RF electrode. The institutional animal care and use committee approved this study. The targeting of paint balls within phantoms was performed under ultrasonography guidance by 2 radiologists (beginner vs expert) with an "in-plane" and "out-of-plane" approaches using the new RF electrode and a conventional RF electrode (n = 20 for each method). To evaluate the targeting performance, the electrode placement time and the number of electrode pullbacks for redirection were compared between the 2 electrodes. The ablation performance was also compared by analyzing the ablation volumes in ex vivo bovine and in vivo porcine livers (n = 30 and n = 24, respectively) and the cellular viability of the ablation zone in in vivo specimens. In the phantom study, the RF electrode embedded with an EMPS showed a significantly shorter electrode placement time compared with the conventional RF electrode in both the in-plane and out-of-plane approaches by both radiologists (P < 0.05). The electrode pullback rate for both radiologists was lower in the new RF electrode than in the conventional RF electrode, but it did not reach statistical significance in the in-plane approach by the expert (P = 0.059). The ablation volumes analyzed with and without cellular viability in the ex vivo and in vivo studies were not significantly different between the 2 electrodes (P > 0.05). The RF electrode embedded with an EMPS is faster than the conventional electrode in the electrode placement into the target lesions. The ablation performance is not significantly different between the 2 electrodes.

Bronchial Thermoplasty by Application of Ultrasound Energy

Background: Asthma is a chronic inflammatory disease of respiratory airways, typically marked by spasms in the bronchi of the lungs, causing difficulty in breathing. Although the disease is very well documented, therapies are limited and patients mostly undergo symptom management. Bronchial thermoplasty is a radiofrequency-based treatment for severe asthma approved by Food and Drug Administration (FDA) in 2010 (Alair system, Boston Scientific Inc). Here we propose the use of ultrasound (US) energy to perform bronchial thermoplasty. Our hypothesis is that ultrasound affects bronchial smooth muscle at least as effective as radio-frequency (RF) but causes less collateral damage, and holds the potential to reduce the procedure time. In this publication we present a direct comparison of acute thermoplasty effects of RF energy versus ultrasound energy. Objective: To evaluate a bronchoscopic procedure based on circumferential ultrasound energy and its effect on bronchial wall structures in comparison to RF thermoplasty for asthma treatment. Methods: This is an observational study aiming for a direct comparison of an ultrasound system with existing asthma therapy based on radio-frequency. Mongrel dogs were used for optimization of ultrasound energy (300 J, 200 J, 100 J) with a 4.5 and 5.5 mm balloon catheter. 100 J was ultimately directly compared with RF effects on bronchial wall structures. Safety and efficacy of the ultrasound system was already previously established during renal denervation clinica stdies. Results: 12 mongrel dogs were used. Bronchoscopy procedures were feasible in all cases, and no adverse effects were seen in any dogs. Lungs were collected for histology and H&E staining. With the optimized 100 J ultrasound energy we observed mild bronchial tissue injury, with minimal hemorrhage and preservation of respiratory epithelium. The RF catheter caused distinct focal injury points resulting from direct contact of the RF electrodes with bronchial wall tissue. Acute histological examination shows hemorrhagic injury along the RF energy path with significant necrosis to all bronchial wall elements including respiratory epithelium. Conclusion: Ultrasound energy is safe, feasible, and at least as effective in affecting bronchoconstriction as RF energy offering a viable alternative to radiofrequency-based lung disease treatments.

Computer modeling and ex vivo experiments with a (saline-linked) irrigated electrode for RF-assisted heating.

BackgroundExternally irrigated radiofrequency (RF) electrodes have been widely used to thermally ablate tumors in surface tissue and to thermally coagulate the transection plane during a surgical resection. As far as we know, no mathematical model has yet been developed to study the electrical and thermal performance of these electrodes, especially the role of the saline layer that forms around the electrode.MethodsNumerical models of a TissueLink device model DS3.0 (Salient Surgical Technologies, Portsmouth, NH, USA) were developed. Irrigation was modeled including a saline layer and a heat convection term in the governing equation. Ex vivo experiments based on fragments of bovine hepatic tissue were conducted to obtain information which was used in building the numerical model. We compared the 60°C isotherm of the computer results with the whitening contour in the heated samples.ResultsComputer and experimental results were in fine agreement in terms of lesion depth (2.4 mm in the simulations and 2.4 ± 0.6 mm in the experiments). In contrast, the lesion width was greater in the simulation (9.6 mm vs. 7.8 ± 1.8 mm). The computer simulations allowed us to explain the role of the saline layer in creating the thermal lesion. Impedance gradually decreased as heating proceeded. The saline was not observed to boil. In the proximity of the electrode (around 1 mm) the thermal lesion was mainly created by the RF power in this zone, while at a further distance the thermal lesion was created by the hot saline on the tissue surface by simple thermal conduction. Including the heat convection term associated with the saline velocity in the governing equation was crucial to verifying that the saline layer had not reached boiling temperature.ConclusionsThe model reproduced thermal performance during heating in terms of lesion depth, and provided an explanation for: 1) the relationship between impedance, electrode insertion depth, and saline layer, and 2) the process of creating thermal lesions in the tissue with this type of electrode.

Radiofrequency Ablation Is a Thyroid Function–Preserving Treatment for Patients with Bilateral Benign Thyroid Nodules

PurposeTo evaluate the efficacy and safety of radiofrequency (RF) ablation for treatment of bilateral thyroid nodules as well as preservation of thyroid function. Materials and MethodsBetween January 2007 and October 2012, 18 patients (16 women and 2 men; mean age, 49.9 y; median age, 44 y; age range, 27–81 y) with bilateral thyroid nodules treated by RF ablation were included in this study. The inclusion criteria included bilateral thyroid nodules, pressure symptoms or cosmetic problems, cytologic confirmation of benignancy without atypical cells, and patient refusal of surgery. We used an RF generator (Cool-tip RF system [Covidien, Boulder, Colorado] or SSP-2000, Taewoong Medical Co, Ltd [Gyeonggi-do, Republic of Korea]) and an 18-gauge internally cooled electrode with 1-cm active tips (Cool-tip [Covidien] or Well-Point RF electrode [Taewoong Medical Co, Ltd]). RF ablation was conducted using the moving shot technique and a trans-isthmic approach. RF ablation was performed in separate sessions for nodules in each lobe. Follow-up ultrasound examinations were performed at 1–6 months, 6–12 months, and during the last month of follow-up. The diameter and volume of the nodule and clinical problems including cosmetic and symptom scores were evaluated before and after the procedure. ResultsThe mean initial nodule size was 4.1 cm ± 1.9, although there was a significant decrease by the time of the last follow-up examination (range, 1–48 mo; mean, 18.1 mo ± 12.8; P < .001, 2.5 cm ± 1.4). The initial nodule volume was 24.4 mL ± 32.2 and was decreased at the last follow-up (6.3 mL ± 19.0, P < .001), with a mean volume reduction of 75.9% ± 19.0. The symptom (P < .001) and cosmetic (P < .001) scores were decreased. Serum hormone levels did not differ significantly before treatment and at the last follow-up (P > .05). ConclusionsRF ablation improves cosmetic problems and symptoms and preserves thyroid function in patients with bilateral thyroid nodules.

Deposition of stable amine coating onto polycaprolactone nanofibers by low pressure cyclopropylamine plasma polymerization

Amine-rich films are of high interest for the bio-applications including drug delivery and tissue engineering thanks to their high reactivity allowing the formation of the covalent linkages between biomolecules and a surface. However, the bio-applications of amine-rich films require their good stability in water which is often achieved at large expenses of the amine concentration. Recently, non-toxic cyclopropylamine (CPA) has been applied for the plasma polymerization of films bearing high NHx environment combined with the moderate thickness loss (20%) after water immersion for 48h. In this work, the amine-rich film with the NHx concentration over 7at.% was deposited on Si substrates and polycaprolactone nanofiber meshes by using CPA plasma polymerization (pulsed mode) in a vertically oriented stainless steel reactor. The substrates were placed at the radio frequency electrode and the ion bombardment caused by direct-current self-bias was suppressed by using high pressure of 50Pa. Analysis of samples by scanning electron microscopy did not reveal any cracks in the deposited layer formed during a sample immersion in water. Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) confirmed a slight oxidation of amine groups in water but the film still contained 5at.% of NHx (according to the N1s XPS fitting) after the immersion. The rapid oxidation of amine groups was observed during the aging experiment carried out in air at room temperature because FTIR revealed an increase of amide peaks that increased progressively with aging time. However, this oxidation was significantly reduced if the plasma polymer was stored at −20°C. Since the films exhibit high amine concentration and very good water stability they have great potential for applications as biocompatible functional coatings.

Холодноплазменная обработка мягких тканей сустава: модельные испытания на суставе крыс

The effect of the radiofrequency ablation on the healing of experimental mechanical damage, formed in the synovium, menisci, and fat body in the rat knee joints was analyzed in this paper. To generate a cold plasma the bipolar radiofrequency electrode “CoVac 50 Wand” of apparatus ‘Atlas’ (ArthroCare, USA), applied in modes 3 (150 V, 68 W) and 6 (225 V, 160 W) was used. The results of the healing of the spontaneous regeneration and after cold ablation monitored within 3 and 6 weeks after the injury were presented. Dimensionless surface factor, estimated volume of the regeneration, and numerical density of cells was used to prove morphologically the beneficial effect of radiofrequency ablation. As a result, the optimal effect of this impact procedure was shown in respect of the restoration of meniscus defects in mode of 6 (225 V, 160 W) and the restoration of synovium and fat body defects in mode of 3 (150 V, 68 W). It was recommended the treatment of fat body by gentle way. It was shown that the phenomenon of «smoothing-maker» doesn’t typical for the soft tissues, and coblative processing even in an optimal mode only contributes to the formation of a thin scar in the place of tissue defects.

Percutaneous Radiofrequency Ablation of Benign Thyroid Nodules Assisted by a Virtual Needle Tracking System

Our aim was to assess the feasibility and outcome of ultrasound (US)-guided percutaneous radiofrequency (RF) ablation of benign thyroid nodules assisted by a real-time virtual needle tracking (VT) system. Forty-five patients (34 females, mean age ± standard deviation (SD): 44 ± 16 y, range: 29–68 y) with 45 benign non-functioning thyroid nodules (mean volume ± SD: 13.5 ± 6.7 mL, range: 12–22 mL) underwent VT-assisted US-guided RF ablation. Nodule volume was evaluated before treatment and during 6-mo of follow-up. Complication rates and patient satisfaction after treatment were also evaluated. By use of the VT system, the tip of the RF electrode was identified during all ablation procedures. The overall mean volume reduction and complication rate were 72.6 ± 11.3% and 2.5%, respectively. Overall satisfaction at the 6-mo follow-up was rated by patients as positive in 42 cases (93%). The VT system could be useful in thyroid nodule ablation procedures because it is able to track the RF electrode tip even when the tip is obscured by the bubbles produced by the ablative process. VT-assisted RF ablation can be a tolerable, non-surgical treatment for patients with benign non-functioning thyroid nodules.