Active Tip Research Articles

Magnetic Positioning System and Ultrasound Guidance for Lumbar Zygapophysial Radiofrequency Neurotomy

Chronic low back pain related to degenerative spondylosis is commonly managed by the radiofrequency ablation of sensory nerves. Fluoroscopic guidance has been considered mandatory to ensure placement of the active tip of the cannula parallel to the nerve to provide adequate neurolysis. Conversely, analgesic (or diagnostic) blockade is usually accomplished by placing the needle perpendicular to the nerve using either fluoroscopy or ultrasound (US) guidance. The recently introduced disposable equipment of internally cooled radiofrequency allows the denervation procedure to be performed similarly to the routine diagnostic block. Consequently, US may now potentially be used for image-guided radiofrequency neurotomy. We sought to compare the accuracy using a novel US-based technique with the traditional fluoroscopy-guided placement. The proof of concept study was performed using a magnetic positioning US-guided system. The precision of needle placements was compared with the standard fluoroscopic guidance. The primary outcome of this study was defined as the procedural accuracy. Procedural and radiation exposure time was also recorded. In addition, projected operational expenses were calculated. Ultrasound-guided procedural accuracy reached 97%. Both the imaging and procedure times were similar between the 2 forms of imaging guidance. Of significant importance, the US-guided approach (no radiation exposure) was quantitatively advantageous over fluoroscopy-guidance, which required an average of 170 seconds of radiation per procedure. Thus, the US method seems to be cost effective. A magnetic positioning system allows accurate and quick US-guided placement of radiofrequency cannula to the desired anatomical targets, sparing patients and personnel from exposure to ionized radiation.

Designing 3D Conical-Shaped Lithium-Ion Microelectrodes

The effect of geometry on the power density and chemical stresses is assessed for a half cell three-dimensional LiCoO2 cathode structure. Simulations demonstrate that for an individual unit cell, as the aspect ratio of the 3D structure increases, its charge capacity decreases by 50%, but its structural integrity improves by approximately 40% as compared to its thin film counterpart. Calculations show that the constructive superposition of an array of conical structures can provide an enhanced instantaneous power density, in agreement with experimental results. This effect occurs because the back of the electrode is electrochemically shielded by the electrochemically active 3D tip. Mechanically, during galvanostatic discharge, chemical stresses become tensile at the electrolyte ∣ electrode tip interface and more compressive at the electrode ∣ back contact interface, as a result of the electric field focusing at the tip of the 3D structure. When the aspect ratio of the 3D structure increases, the conical structure mechanically relaxes the substrate, thus reducing the possibility of mechanical failure-induced capacity loss. A critical aspect ratio that maximizes the discharge stresses, ξ′=0.32 was identified.

Polysiloxane‐Derived Ceramics Containing Nanowires with Catalytically Active Tips

By direct foaming of a Pt‐containing polysiloxane precursor, macroporous ceramics were generated by pyrolysis at 1400°C under nitrogen or argon. The growth of nanowires was induced via a vapor–liquid–solid mechanism in which the Pt particles acted as deposition site for the decomposition gases released upon pyrolyzing the preceramic polymer. SEM, HR‐SEM, TEM/EDX, and XRD investigations revealed that pyrolysis under argon atmosphere leads to short SiC nanowires of only a few micrometers length and under nitrogen atmosphere Si3N4 nanowires evolved, with length of several 10 μm. In both cases the tips of the nanowires mainly consisted of PtSi. In contrast to samples pyrolyzed at 600°C, the components after higher temperature pyrolysis showed moderate‐specific surface areas of 55–67 m2/g. In CO oxidation experiments, a good catalytic activity was found for the Pt silicide particles, suggesting that despite their relatively large size, their location at the tips of the nanowires affords them good reactivity.

CT-Guided Percutaneous Pulse-Dose Radiofrequency for Pudendal Neuralgia

The purpose of our study was to evaluate the efficacy of computed tomography (CT)-guided percutaneous pulse-dose radiofrequency (PDRF) for the treatment of chronic pain in patients with pudendal neuralgia (PN) unresponsive to conservative approaches. From March 2010 to January 2012, 30 patients with a diagnosis of PN were prospectively enrolled in the study, 18 women and 12 men (mean age 47 years). A 20-gauge cannula with a 10-cm length was placed under CT guide in the pudendal (Alcock's) canal. After the spindle was removed, a radiofrequency needle with a 5-mm active tip was introduced. The appropriate needle placement near the pudendal nerve, without an involvement of the vessels, was confirmed with an injection of 1-2 ml of contrast agent. PDRF was performed with 1,200 pulses at high voltage (45 V) with 20 ms duration followed by 480 ms silent phases. Twenty-six patients completed the study. Procedural success was achieved in all patients. Mean VAS scores before PDRF was 9 ± 0.7. Patients had a great improvement in pain intensity after 1 week by PDRF (mean VAS scores 3.8 ± 1.7, p < 0.05), with a stabilization of the symptomatology in the following months (mean VAS scores 1.5 ± 1.1 at 6 months by PDRF, p < 0.05) and excellent results after 1 year by the procedure (mean VAS scores 1.9 ± 0.7, p < 0.05). In our preliminary experience, CT-guided percutaneous PDRF should be recommended for treatment of PN because we evaluated the tolerability of this procedure with satisfactory and encouraging results.

Pulse-Dose Radiofrequency for Knee Osteoartrithis

Knee osteoarthritis (OA) is a leading cause of disability in the elderly. The purpose of this study was to investigate the effectiveness of pulse-dose radiofrequency (PDRF) in patients with chronic pain refractory to conservative therapies. Between January 2011 and November 2012, PDRF was performed on 40 patients. A 20-gauge cannula, 10 cm in length, was introduced in the antero-lateral region of the interested knee, and its tip was placed in the joint space under fluoroscopic guidance. After the spindle was removed, an RF needle with a 10-mm "active tip" was introduced. PDRF was performed with 1,200 pulses at high voltage (45 V) with 20-ms duration followed by a 480-ms silent phase. Mean VAS scores before the procedures was 6.8 ± 0.8. A great decrease of pain intensity was achieved 1 week after PDRF (mean VAS scores 1.8 ± 0.4 [p < 0.05]) with stabilization of painful symptomatology in the following months and excellent results 1 year after treatment (mean VAS scores 2.3 ± 0.6 after 12 months [p < 0.05]). Western Ontario and McMaster Universities Index of Osteoarthritis scores showed improved quality of life in all patients at 6 months (p < 0.05) and at 1 year (p < 0.05) after PDRF. No patients developed complications. This study successfully investigated the effectiveness of PDRF in patients with chronic pain unresponsive to conservative therapies. PDRF seems to be an effective and reliable technique for palliative management of chronic pain in patients with knee OA.

Active generalized predictive control of turbine tip clearance for aero-engines

Active control of turbine blade tip clearance continues to be a concern in design and control of gas turbines. Ever increasing demands for improved efficiency and higher operating temperatures require more stringent tolerances on turbine tip clearance. In this paper, a turbine tip clearance control apparatus and a model of turbine tip clearance are proposed; an implicit active generalized predictive control (GPC), with auto-regressive (AR) error modification and fuzzy adjustment on control horizon, is presented, as well as a quantitative analysis method of robust perturbation radius of the system. The active clearance control (ACC) of aero-engine turbine tip clearance is evaluated in a lapse-rate take-off transient, along with the comparative and quantitative analysis of the stability and robustness of the active tip clearance control system. The results show that the resultant active tip clearance control system with the improved GPC has favorable steady-state and dynamic performance and benefits of increased efficiency, reduced specific fuel consumption, and additional service life.

Intradiscal Pulsed Radiofrequency for Chronic Lumbar Discogenic Low Back Pain: A One Year Prospective Outcome Study Using Discoblock for Diagnosis

Background: Discogenic pain is an important cause of low back pain (LBP). We have developed a pulsed radiofrequency (PRF) technique, using Diskit II® needles (NeuroTherm, Middleton, MA, USA) placed centrally in the disk, for applying radiofrequency current in the disc (Intradiscal PRF method). Objective: The purpose of this study was to investigate the effect of this intradiscal pulsed radiofrequency method in patients with chronic discogenic LBP diagnosed by discoblock, in terms of pain relief and reduction of disability. Study Design: Prospective case series clinical outcome study. Methods: The participants consisted of 23 patients with a mean age of 35.3 ± 9.86 years with chronic discogenic LBP that was not responsive to aggressive nonoperative care. A Diskit II needle (15-cm length, 20G needle with a 20-mm active tip) was placed centrally in the disc. PRF was applied for 15 minutes at a setting of 5 × 5 ms/s and 60 V. Outcome measures included the pain intensity score on a 0-10 numeric rating scale (NRS) and the Roland-Morris Disability Questionnaire (RMDQ) at pre-treatment, one, 3, 6, and 12 months post-treatment. Results: The mean pain severity scores (NRS) improved significantly from 7.47 ± 0.85 pretreatment to 3.13 ± 2.58 at the 12 month follow-up (P &lt; 0.01). The RMDQ showed significant (P &lt; 0.01) improvement from 11.4 ± 1.57 pre-treatment to 2.90 ± 2.97 at the 12 month follow-up (P &lt; 0.01). Nineteen of 23 (82.6%) of the patients demonstrated NRS improvements of greater than 2, and 15 of 23 (65.2%) had &gt; 50% pain reduction, 12 months after treatment. Limitations: The number of patients was relatively low and secondary outcomes such as medication requirement or psychological effects were not addressed. Conclusions: This intradiscal PRF method with consecutive PRF 5/5/60V, 15 min (with Diskit needle) appears to be a safe, minimally invasive treatment option for patients with chronic discogenic LBP. Key words: Pulsed radiofrequency, discogenic pain, intradiscal procedures, chronic low back pain, Roland-Morris Disability Questionnaire

Morphological evaluation of the active tip of six types of orthodontic mini-implants

To morphologically evaluate the active tip of six different types of self-drilling mini-implants for orthodontic anchorage. Images of the active tips of the mini-implants were obtained with a Zeiss optical microscope Stemi 200-C, with magnification of 1.6X. The images of the surface were viewed with the Axio Vision program (Zeiss, Jena, Germany) to calculate linear and angular measures. Mini-implant morphology and the details of tips and threads were also evaluated through Scanning Electronic Microscopy (SEM) (JEOL, model JSM5800 LV - JEOL, Tokyo, Japan) with magnifications of 90X and 70X, respectively. The evaluation of the mini-implant taper shape was assessed using the formula: (b - a) / (2 x D). The following variables were measured: (1) active tip width, (2) major diameter of external thread, (3) minor diameter of internal thread and taper of the mini-implant, (4) number of threads and lead of the screw, (5) angle of thread, (6) flank width and (7) pitch width. Mini-implants from different manufacturers presented active tips with different characteristics. Mechanical testing is necessary to correlate the analyzed characteristics aiming to determine the best performance.

1:46 PM Abstract No. 83 - Radiofrequency (RF) ablation of normal liver increases tumor growth of remote subcutaneous tumors in an animal tumor model

Purpose To characterize the effect of radiofrequency (RFA) ablation of normal liver on tumor growth of remote tumors. Materials and Methods R3230 breast tumors were subcutaneously implanted into female Fisher rats (n=14). When tumors reached 10mm in diameter, animals were randomized (n=7/arm) to either receive RF to normal liver (21g electrode, 1 cm active tip, standardized to tip temperature of 70°C x 5 min via exploratory laparotomy) or to the control group (sham treatment, with needle placement in liver but no RFA). Tumor growth was measured for 7d after treatment, followed by animal sacrifice and tumor harvest to enable immunohistochemistry for proliferative index calculations (% cells positive for Ki-67 staining). Tumor growth curves before and after treatment were also analyzed. Results While tumors in RFA and sham groups were the same size at the time of treatment (11.0±0.7mm vs. 11.3±0.3mm, p=0.48), a significantly greater tumor growth rate was observed in the RFA group such that tumors were significantly larger at 7d compared to sham-treated animals (17.0±2.1mm vs. 13.2±0.8, p=0.02), representing an increase in tumor size by 34.8±0.1% vs. 13.7±0.1% (p Conclusion Although RF ablation of normal liver is necessary to achieve an ablative margin, it can stimulate the growth of tumors remote from the ablation site and external to the treated organ in at least one animal model. Additional studies are required to confirm these findings in other tumor types and clinical scenarios and to assess whether this potentially deleterious acceleration of tumor growth can be reversed through pharmacologic therapy.

4:10 PM Abstract No. 50 - Pharmacomechanical pulverization of mycetoma in the renal collecting system

Purpose Renal mycetomas are rare manifestations of candidia infection in children, which if untreated may lead to urinary tract obstruction (UTO), renal failure and high mortality. We report successful use of an AngioJet device to pulverize an obstructing renal pelvis candida mycetoma resistent to conventional nephrostomy tube (NT) drainage in a small child with UTO and renal failure. Materials and Methods Case history : A 2.5 year old, 10.5 kg, former 26 wk premature girl was admitted with recurrent candida urinary tract infection and fungal balls within the right pelvicalyceal system leading to UTO, oliguria and renal failure (serum Cr 2.7 mg/dL). NT placement and administration of IV Amphotericin B (AmB) failed to improve urine output or renal failure. Ultrasound and antegrade pyelogram showed persistent dilatation of an obstructed right collecting system plugged with fungal balls. Technique : The in situ 8.5F NT catheter was exchanged for a vascular sheath through which a 6-French AngioJet Spiroflex catheter (AngioJet ® Ultra thrombectomy system, Medrad International ® ) with a 15-mm active tip was advanced into the renal pelvis and calyces under ultrasound and fluroscopic monitoring. Fungal balls were drawn into the catheter,fragmented by saline pressure jets from the active tip and aspirated simultaneously. The saline in the AngioJet system was replaced with AmB solution and pharmacomechanical pulverization of the fungal balls was performed followed by upsizing of the NT to 10F. Results After mycetoma pulverization, NT urine output improved from 0 to 490mL in the first 12 hr, and serum Cr decreased to 1.65 within 24 hr. The patient had no complications from the AngioJet therapy. She completed a 21 day course of systemic and transcatheter AmB and NT was removed. At 2 week follow-up, serum Cr was 0.6 mg/dL, and ultrasound and antegrade studies showed reduced hydronephrosis with no recurrence of fungal balls. At 12 month follow- up, patient had no recurrence of candida infection, no imaging recurrence of mycetoma and serum Cr 0.5 mg/dL. Conclusion Pharmacomechanical pulverization using an AngioJet thrombectomy system is an effective treatment option for refractory renal collecting system mycetoma.

Abstract No. 377 - CT findings after irreversible electroporation ablation in a porcine model: Radiologic-pathologic correlation

Purpose To characterize computed tomography (CT) findings after irreversible electroporation (IRE) in a porcine model Materials and Methods Twenty two CT-guided IRE lesions were created in livers of 12 pigs. Energy was delivered at 2250-3000 V (pulse length, 90-100 μsec; pulse repetition, 70-90) by using two 18-gauge electrodes with 2-2.5 cm active tip, 1.5-2.0 cm distance between electrodes and a Nanoknife generator (Angiodynamics, Fremont, CA). Triple-phase multi-detector CT imaging was performed prior to IRE application and immediately before euthanasia (2 hours after ablation). Multiple CT imaging features were studied, including: dimensions; coagulation zone attenuation; and presence, as well as characteristics of post ablation enhancement. Zones of ablation were evaluated at gross and histopathologic examination, correlated with CT findings, and subjected to statistical analysis. Results The mean ablation volume measured by CT imaging and gross pathology was 31.8 cm 3 [95% CI: (14.3, 49.4)] and 15.2 cm 3 [95% CI: (12.8,17.6)]. Using a mixed-effects regression model, the two volume means are significantly different (p=0.04) with the size of the ablation zone on the CT appearing larger than the gross size (p=0.0416). Two hours after IRE energy application, the ablation zone appeared as a well demarcated hypoattenuating area. Mean pre, arterial and portal HU for the zone of ablation was 79.6 [95% CI: (73.1, 87.2), 64.3 [95% CI: (57.3, 72.0)], and 73.9 [95% CI: (61.8, 86.1). An incomplete rim of enhancement was observed surrounding the zone of ablation in both the arterial and portal phase with a median thickness of 2.5 mm. Histologic examination revealed a clear demarcation between the ablated liver and adjacent unaffected parenchyma. Coagulation zone was characterized by hepatocellular dissociation often associated with hemorrhage and sinusoidal dilatation. Conclusion CT imaging in the acute period after IRE depicts the ablation zone as a hypoattenuating lesion with a surrounding rim of enhancement. However, it appears to overestimate the dimensions of the ablative injury.

Use of Intra-Articular and Intrabursal Pulsed Radiofrequency for the Treatment of Persistent Arthrogenic Shoulder Pain

Dear Editor: Shoulder pain is one of the most common types of joint pain, with an estimated lifetime prevalence of 67% among adults ⇓. Despite readily available treatments, chronic shoulder pain often results in substantial disability. Although the utility of pulsed radiofrequency (PRF) for relieving diarthrodial joint pain has been reported ⇓, no long-term follow-up has been documented, and only a single-needle technique has been used either intra-articularly or in subscapular areas of the shoulder. This article describes three cases with persistent arthrogenic shoulder pain for whom long-term pain relief was achieved with intrabursal PRF treatment delivered by a 20-gauge, 15-cm insulated needle with a 10-mm active tip at 42°C. Current delivery was at 500 KHz applied at 2 bursts/second, with each burst lasting 20 milliseconds for a total of 360 seconds. Case 1 was a 36-year-old Caucasian woman injured in a motor vehicle accident who complained of persistent severe burning and stabbing pain in the right shoulder that was exacerbated with any movement. Nonsteroidal anti-inflammatory drugs (NSAIDs) and oral narcotics temporarily relieved night pain. Additional treatment included 1 year of physical therapy and two intra-articular corticosteroid injections. One year following her injury, the patient reported a pain score of 8/10 on the visual analog scale (VAS) ⇓ at rest. After being diagnosed with rotator cuff tendinitis with partial thickness tearing and degenerative arthritis with acromioclavicular (AC) joint pain, the patient underwent right shoulder arthroscopy with subacromial decompression and open distal clavicle excision. Pain …

Microwave ablation devices for interventional oncology

Microwave ablation is one of the several options in the ablation armamentarium for the treatment of malignancy, offering several potential benefits when compared with other ablation, radiation, surgical and medical treatment modalities. The basic microwave system consists of the generator, power distribution system and antennas. Often under image (computed tomography or ultrasound) guidance, a needle-like antenna is inserted percutaneously into the tumor, where local microwave electromagnetic radiation is emitted from the probe’s active tip, producing frictional tissue heating, capable of causing cell death by coagulation necrosis. Half of the microwave ablation systems use a 915 MHz generator and the other half use a 2450 MHz generator. To date, there are no completed clinical trials comparing microwave devices head-to-head. Prospective comparisons of microwave technology with other treatment alternatives, as well as head-to-head comparison with each microwave device, is needed if this promising field will garner more widespread support and use in the oncology community.

Highly efficient low voltage electron emission from directly spinnable carbon nanotube webs

Two methods for increasing the number of free carbon nanotube (CNT) tips in carbon nanotube webs (CNTW) and improving their field emission (FE) performance are proposed. It was observed that by laterally compressing samples by 35 percent it is possible to improve FE performance to some extent, with further compression leading to a loss of FE properties due to folding of webs and adhesion between CNT tips. Multilayered samples were also studied and it was found that samples with successive layers in which the orientation of the nanofibers in successive layers was the same, increased inter-bundle van der Waals forces, leading to more compact webs with no improvement in FE performance. However, it was found that if the fibers in successive layers were perpendicular to each other the inter-bundle attraction was minimized, maximizing the number of active CNT tips and yielding materials that exhibit the best FE performance reported for any material to date.

Thyroid surgery – intraoperative localization and protection of important structures of the neck

Nodular thyroid disease affects 500 to 600 million people worldwide. Tumours of the thyroid account for about 1% overall human cancers. Thyroidectomy is the most common endocrine operation. Surgical treatment for benign thyroid nodules is recommended for: progressive increase in nodule size, substernal extension, compressive symptoms in the neck region, the development of thyrotoxicosis and in case of preference of that kind of treatment reported by the patient. In Poland thyroidectomy is the fourth surgical procedure and concerns 25000 operations yearly. Reduction of surgical injury with simultaneous retention of current safety and radical nature of surgical procedure forces the work in a relatively small operating field. Electric devices enabling the achievement of full and lasting haemostasis during thyroidectomy supplant traditional surgical method (ligature, haemostatic sutures) with no impact on the incidence of perioperative complications, while at the same time allowing to shorten the duration of the procedure. The haemostatic effect is associated with generation of heat, which apart from the intended result may bring about thermal tissue injury. During the surgical procedure important is to determine the thermal spread around the active tip of electric devices in the operating field during thyroidectomy, and the safe temperature range during the operation to protect important structures of the neck. The mean safe distance of the active tip of an electric device from important anatomic structures is 5mm minimally and depends on the device type, time of using and its power settings. All the modern techniques of vessel sealing are associated with generation of heat and its spherical spread, which causes thermal injury to the surrounding tissues. Their mode of operation through, among others, structural changes in collagen and elastin, leads to lasting joining of sealed vessel walls and tissue structures. These systems enable a safe sealing of vessels of up to 7mm in diameter. In conclusions: In the cases analysed by the author concerning the thyroidectomy techniques, it is recommended to replace to electric devices with ligatures or clips or human fibrinogen in place near the laryngeal nerves, parathyroid glands and the trachea. The decision on the change of the method of haemostasis maintenance in the vicinity of crucial structures belongs to the surgeon.

A Novel Generalized Predictive Control and its Application on Active Clearance Control of Aero-Engine

Turbine blade tip clearance continues to be a concern in the design and control of gas turbines. Ever increasing demands for improved efficiency and higher operating temperatures require more stringent tolerances on turbine tip clearance. An implicit active generalized predictive control with AR error modification and fuzzy adjustment on control horizon of aero-engine turbine tip clearance is presented and evaluated. The results show the resultant active tip clearance control system has good steady and dynamic performance and benefits of increased efficiency, reduced specific fuel consumption, and additional service life.

Patients’ survival in lung malignancies treated by microwave ablation: our experience on 56 patients

ObjectivesWe retrospectively evaluated percutaneous CT-guided microwave (MW) ablation safety and efficacy in unresectable lung malignancies focusing on patients’ survival. Materials and methodsAll procedures were approved by the hospital ethical committee. From 2008 to 2012 we treated 69 unresectable lesions (44 lung cancer, 25 lung metastases) in 56 patients (35 men/21 women; mean age: 61.5years). Treatment was performed under CT guidance using 14G needles with a 3cm active tip and a 55W MW generator (Vivawave Microwave Coagulation System; Valley Lab). Treatment was performed at 45W for 6–10min. Patients were scheduled for a 3 and 6month CT follow-up to evaluate lesion diameter and enhancement. Survival rate was evaluated by Kaplan–Meier analysis. ResultsAblation procedures were completed according to protocol in all patients. Pneumothorax occurred in 18 patients and 8 required chest tube. Four lesions (all >4.3cm) were retreated 20days after the ablation because of peripheral focal areas of residual tumor. Follow-up CT evaluation showed a decrease in maximum diameter in 44/69 lesions (64%) and in 42/59 lesions (71%) at 3 and 6months, respectively. In all cases no pathologic enhancement was observed. Cancer-specific mortality yielded a survival rate of 69% at 12months, 54% at 24months and 49% at 36months, respectively. An estimate mean for survival time was 27.8months with a standard error of 2.8months (95% confidence interval: 22.4–33.2months). ConclusionBased on our experience, MW ablation seems to represent a potential safe and effective percutaneous technique in the treatment of lung malignancies. MW ablation may improve survival in patients not suitable to surgery.

The origin and geochemical evolution of the Woodlark Rift of Papua New Guinea

Geochemical, isotopic, and geochronologic data for exhumed rocks in the Woodlark Rift of Papua New Guinea (PNG) allow a tectonic link to be established with the Late Cretaceous Whitsunday Volcanic Province (WVP) of northeastern Australia. Most of the metamorphic rocks in the Woodlark Rift have Nd isotopic compositions (εNd=+1.7 to +6.2) similar to the Nd isotopic compositions of rocks in the WVP (εNd=+1.3 to +6.6; Ewart et al., 1992), and contain inherited zircons with 90 to 100Ma U–Pb ages that overlap the timing of magmatism in the WVP. None of the metamorphic rocks in the Woodlark Rift have the highly evolved Hf and Nd isotopic compositions expected of ancient continental crust. Magmas were erupted in the WVP during the middle Cretaceous as eastern Gondwana was rifted apart. The protoliths of felsic and intermediate metamorphic rocks in the Woodlark Rift are interpreted to be related to the magmatic products produced during this Cretaceous rifting event. Some mafic metamorphic rocks exposed in the western Woodlark Rift (eclogites and amphibolites) are not related to the WVP and instead could have originated as basaltic lavas crystallized from mantle melts at (U)HP depths in the Late Cenozoic, or as fragments of Mesozoic aged oceanic lithosphere.Isotopic and elemental comparisons between basement gneisses and Quaternary felsic volcanic rocks demonstrate that felsic lavas in the D'Entrecasteaux Islands did not form solely from partial melting of metamorphic rocks during exhumation. Instead, the isotopic compositions and geochemistry of Quaternary felsic volcanic rocks indicate a significant contribution from the partial melting of the mantle in this region. When combined with geophysical data for the western Woodlark Rift, this suggests that future seafloor spreading will commence south of Fergusson Island, and west of the present-day active seafloor spreading rift tip.

Pulsed radiofrequency in peripheral posttraumatic neuropathic pain: A double blind sham controlled randomized clinical trial

Background and purposePulsed radiofrequency (PRF) is widely used for the treatment of chronic pain, although its mechanism of action is not known. The evidence of efficacy of PRF for neuropathic pain (NP) conditions is limited. A double-blind, randomized, sham-controlled parallel study was conducted to evaluate the efficacy and safety of PRF in the treatment of peripheral posttraumatic NP. MethodsForty-five patients with peripheral posttraumatic NP in their upper or lower limb were randomly assigned to receive PRF or sham treatment to the injured peripheral nerve(s) causing peripheral posttraumatic NP. Only patients whose pain intensity was at least 5 on numerical rating scale (NRS) 0–10 and who had suffered from their NP for at least 6months were included. All patients had dynamic mechanical allodynia or pinprick hyperalgesia in their painful area. They had achieved temporary pain relief of at least 50% with a local nerve block performed at a previous visit. The primary efficacy variable was the difference in 3-day mean pain intensity score from the baseline to 3months. Other variables included response defined as ≥30% reduction in mean pain intensity at 3months compared to baseline, Neuropathic Pain Scale (NPS) results, health related quality of life (SF-36) and adverse effects. The skin was anesthetized with 1% lidocaine. A radiofrequency needle was introduced through the skin, and then guided to a SMK cannula (52, 100 or 144mm depending on the target nerve) with 4 or 5mm active tip (SMK-C5-4, SMK-C10-5, SMK-C15-5, Radionics®, Burlington, MA, USA). The nerve was located accurately by stimulating at 50Hz (threshold <0.5V). Sham treatment or PRF was applied for 120s 1–4 times at each treatment point (Radionics®, Burlington, MA, USA). The total treatment time was up to 8min. Both patients and clinicians were blinded during the whole treatment and follow-up period. ResultsForty-three patients were included in the analyses. There was no statistically significant difference between PRF and sham treatment for the primary outcome efficacy variable.Seven patients (3 in PRF group and 4 in sham treatment group) achieved ≥30% pain relief (difference between groups was not significant). There was no statistically significant difference in the NPS or any dimension of SF-36 between the treatments. Eighteen patients reported adverse effects. They were mild and did not necessitate any treatment. Transient pain was reported by 17 patients, local irritation by 5 patients and local inflammation by 1 patient. There was no significant difference between the groups in the presence of adverse effects. ConclusionsPRF was well tolerated, but this study failed to show efficacy of PRF over sham treatment for peripheral posttraumatic NP. ImplicationsBased on our results, we do not recommend PRF for peripheral posttraumatic NP. More research of the possible use of PRF for various pain conditions is needed to determine its role in the management of prolonged pains.

Results of Intradiscal Pulsed Radiofrequency for Lumbar Discogenic Pain: Comparison with Intradiscal Electrothermal Therapy

BackgroundWe have developed an intradiscal pulsed radiofrequency (Disc PRF) technique, using Diskit II® needles (NeuroTherm, Wilmington, MA, USA), as a minimally invasive treatment option for chronic discogenic low back pain (LBP). The purpose of this study was to compare the representative outcomes of Disc PRF and Intradiscal Electrothermal Therapy (IDET) in terms of pain relief and reduction of disability.MethodsThirty-one patients with chronic discogenic LBP who underwent either Disc PRF (n = 15) or IDET (n = 16) were enrolled in the study. A Diskit II® needle (15-cm length, 20-gauge needle with a 20-mm active tip) was placed centrally in the disc. PRF was applied for 15 min at a setting of 5 × 50 ms/s and 60 V. The pain intensity score on a 0-10 numeric rating scale (NRS) and the Roland-Morris Disability Questionnaire (RMDQ) were assessed pretreatment and at 1, 3, and 6 months post-treatment.ResultsThe mean NRS was significantly improved from 7.2 ± 0.6 pretreatment to 2.5 ± 0.9 in the Disc PRF group, and from 7.5 ± 1.0 to 1.7 ± 1.5 in the IDET group, at the 6-month follow-up. The mean RMDQ also showed significant improvement in both the Disc PRF group and the IDET group at the 6-month follow-up. There were no significant differences in the pretreatment NRS and RMDQ scores between the groups.ConclusionsDisc PRF appears to be an alternative to IDET as a safe, minimally invasive treatment option for patients with chronic discogenic LBP.