Imaging-Guided Dual-Target Neuromodulation of the Mouse Brain Using Array Ultrasound.

Neuromodulation is an important method for investigating neural circuits and treating neurological and psychiatric disorders. Multiple-target neuromodulation is considered an advanced technology for the flexible optimization of modulation effects. However, traditional methods such as electrical and magnetic stimulations are not convenient for multiple-target applications due to their disadvantages of invasiveness or poor spatial resolution. Ultrasonic neuromodulation is a new noninvasive method that has gained wide attention in the field of neuroscience, and it is potentially able to support multiple-target stimulation by allocating multiple focal points in the brain using an array transducer. However, there are no reports in the literature of the efficacy of this technical concept, and an imaging tool for localizing the stimulation area for evaluating the neural effects in vivo has been lacking. In this study, we designed and fabricated a new system specifically for imaging-guided dual-target neuromodulation. The design of the array transducer and overall system is described in detail. The stimulation points were selectable on a B-mode image. In vivo experiments were carried out in mice, in which forelimbs shaking responses and electromyography outcomes were induced by changing the stimulation targets. The system could be a valuable tool for imaging-guided multiple-target stimulation in various neuroscience applications.

Autonomic Responses to Ultrasound-Guided Percutaneous Needle Electrolysis: Effect of Needle Puncture or Electrical Current?

OBJECTIVE: The aim of this study was to establish if the changes in sympathetic and parasympathetic activity (analyzed through heart-rate variability [HRV]) during ultrasound (US)-guided percutaneous needle electrolysis (PNE) is due to the effect of needle puncture only or of the PNE technique per se where the puncture and galvanic current are combined. METHODS: This was an experimental, case-control study that took place at the University of Seville. Subjects were 36 male footballers who were randomly allocated to three groups: a control group (CG; 12 players), for whom HRV was recorded for 10 min, both at rest and during an exhaustive US examination of the patellar tendon and adjacent structures; a first experimental group (PNE group; 12 players), for whom HRV was recorded for 10 min, both at rest and during application of US-guided PNE in the patellar tendon; and a second experimental group (needle group; 12 players), for whom HRV was recorded for 10 min, both at rest and during application of US-guided PNE without electrical current in the patellar tendon. The outcome measures were the diameters of the Poincaré plot (SD1, SD2), stress score, and sympathetic/parasympathetic ratio. RESULTS: There were no differences between groups in any baseline measurements, nor were there any significant differences between CG measurements (baseline vs. intervention). The PNE group exhibited statistically significant increases in SD1 (p = 0.01) and SD2 (p = 0.004) and statistically significant decreases in SS and S/PS ratio (p = 0.03), indicating increased parasympathetic and decreased sympathetic activity, respectively. The needle group exhibited statistically significant increases in SD2 (p = 0.02) and statistically significant decreases in SS (p = 0.02), indicating decreased sympathetic activity. CONCLUSIONS: The application of the US-guided PNE technique caused a measurable increase in parasympathetic activity (detected by HRV), which was due to the combination of needle puncture and electric current.

How to achieve ultrasound-guided femoral venous access: the new standard of care in the electrophysiology laboratory.

PURPOSE: Bedside vascular ultrasound machines are increasingly available. They are used to facilitate safer vascular access across a number of different specialties. In the electrophysiology laboratory however, where patients are frequently anticoagulated and require the insertion of multiple venous sheaths, anatomical landmark techniques predominate. Despite the high number of vascular complications associated with electrophysiological procedures and the increasing evidence to support its use in electrophysiology, ultrasound remains underutilised. A new standard of care is required. A comprehensive technical report, providing a detailed explanation of this important technique, will provide other electrophysiology centres with the knowledge and justification for adopting ultrasound guidance as their standard practice. METHOD: We review the increasing body of evidence which demonstrates that routine ultrasound usage can substantially improve the safety of femoral venous access in the electrophysiology laboratory. We offer a comprehensive technical report to guide operators through the process of ultrasound-guided venous access, with a specific focus on the electrophysiology laboratory. Additionally, we detail a novel technique which utilises real-time colour Doppler ultrasound to accurately identify needle tip location during venous puncture. CONCLUSIONS: The use of vascular ultrasound to guide femoral venous cannulation is rapid, inexpensive and easily learnt. Ultrasound is readily available and offers the potential to significantly reduce vascular complications in the unique setting of the electrophysiology laboratory. Ultrasound guidance to achieve femoral venous access should be the new standard of care in electrophysiology.

Is Prebiopsy MRI Good Enough to Avoid Prostate Biopsy? A Cohort Study Over a 1-Year Period.

INTRODUCTION: Prebiopsy multiparametric magnetic resonance imaging (MRI) is increasingly used in clinical practice to detect clinically significant prostate cancer, although its role is controversial. We audited the accuracy of prebiopsy MRI for men clinically suspected to have prostate cancer who underwent initial transrectal ultrasound (TRUS) biopsy at our institution. PATIENTS AND METHODS: All patients who had a prebiopsy prostate MRI and initial TRUS prostate biopsy from January 1, 2013 to December 31, 2013 were included in the study. Prostate MRI was performed using a 1.5-T machine with T2 and diffusion weighted imaging axial phase. TRUS prostate biopsy was performed using a monoplane ultrasound machine. Systematic 12-core prostate biopsies were taken with a Tru-Cut biopsy needle from the apex, middle, and base of the left and right lobe. RESULTS: One hundred seventy-three patients met the inclusion criteria; 128 (74.4%) patients had a lesion detected on MRI and 114 (66.3%) patients had a positive biopsy. The sensitivity of MRI for significant prostate cancer on TRUS biopsy of the prostate was 83.5%, specificity was 35.2%, positive predictive value was 55%, and negative predictive value was 68.9%. A positive MRI scan was significantly associated with significant prostate cancer diagnosis, and higher National Comprehensive Cancer Network (NCCN) risk classification (P ≤ .001). MRI detected 62 of 63 NCCN high-risk and 18 of 18 Gleason score 8 to 10 cases. CONCLUSION: The sensitivity and specificity of MRI appears insufficient to avoid TRUS biopsy in all men clinically suspected to have prostate cancer. Standardized MRI reporting and robust prospective studies are needed to define the role of prebiopsy MRI in this setting. For patients at risk of complications from biopsy, a negative MRI scan might be used to exclude high-risk disease.

Wireless Ultrasound Guidance for Femoral Venous Cannulation in Electrophysiology: Impact on Safety, Efficacy, and Procedural Delay.

BACKGROUND: Ultrasound (US) guidance increases safety and efficacy in vascular cannulation and is considered the standard of care. However, barriers including workflow interference and the need to be assisted by a second operator limit its adoption in clinical routine. The use of wireless US (WUS) may overcome these barriers. The aim of this study was to assess the impact of a novel WUS probe during its initial implantation in an electrophysiology (EP) laboratory. METHODS: Thirty-six patients requiring femoral venous cannulation for EP procedures were included in this single center, prospective, observational study, comparing WUS guidance with the anatomical landmark approach. The primary endpoint was time to successful cannulation. Secondary endpoints included rate of unsuccessful punctures, accidental arterial punctures, and workflow interference. RESULTS: Compared with anatomical landmark approach, WUS guidance significantly reduced mean time to successful cannulation (87.3 ± 94.3 vs 238.1 ± 294.7 seconds, P < 0.01). Workflow interference was predominantly nonexistent or mild and decreased after the first three weeks of use. In addition, WUS guidance improved safety and efficacy, reducing the rate of accidental arterial punctures (0.02 ± 0.1 vs 0.25 ± 0.5 arterial punctures per cannulation, P < 0.05) and unsuccessful attempts (0.26 ± 0.8 vs 1.75 ± 2.1 attempts per cannulation, P < 0.01). CONCLUSIONS: WUS guidance resulted in faster, safer, and more effective femoral venous cannulation than the anatomical landmark approach without adding significant workflow interference. The application of wireless technology in this setting contributed to overcoming some of the barriers preventing a more widespread clinical use of US guidance.

The transesophageal echo probe may contribute to esophageal injury after catheter ablation for paroxysmal atrial fibrillation under general anesthesia: a preliminary observation.

INTRODUCTION: The transesophageal echo probe (TEE) is commonly used before and during atrial fibrillation (AF) ablation under general anesthesia (GA). We sought to determine the potential contribution of the TEE probe to esophageal injury after pulmonary vein isolation (PVI) alone for paroxysmal AF. METHODS AND RESULTS: Seventy-six patients undergoing PVI with TEE, PVI/TEE, 16 undergoing PVI without TEE (PVI/No TEE), and 27 undergoing TEE without any left atrial ablation (TEE/No LA ablation) under GA were included. Posterior wall ablation was power (20-25 W) and time limited (electrogram attenuation or ≤30 s). Esophageal capsule endoscopy (n = 206) was performed pre- and post-procedure and at 2 weeks. Esophageal lesions were seen in 30% of PVI/TEE, 0% of patients in the PVI/No TEE (P = 0.009), and 22% of TEE/No LA ablation groups (P = 0.47 vs. PVI/TEE). There were no instances of esophageal bleeding, perforation, or need for gastrointestinal intervention. Self-resolving dysphagia was the only reported symptom (5%). All lesions healed within 2 weeks. There was no significant difference in the location or morphological appearance of esophageal lesions seen in the PVI/TEE versus TEE/No LA ablation groups. CONCLUSIONS: Esophageal lesions were seen in 30% of patients undergoing PVI alone under GA with use of TEE and in a similar proportion (22%) of patients undergoing TEE in the absence of left atrial ablation. This study makes the preliminary observation that one must be cognizant of the TEE probe as a potential contributor to esophageal injury after AF ablation. Larger studies are needed to confirm these findings.

Intracranial dual-mode IVUS and hyperthermia using circular arrays: preliminary experiments.

In this study, we investigated the feasibility of using 3.5-Fr (3 Fr = 1 mm) circular phased-array intravascular ultrasound (IVUS) catheters for minimally invasive, image-guided hyperthermia treatment of tumors in the brain. Feasibility was demonstrated in two ways: (1) by inserting a 3.5-Fr IVUS catheter through skull burr holes, for 20 MHz brain imaging in the pig model, and (2) by testing a modified circular array for therapy potential with 18.5-MHz and 9-MHz continuous wave (CW) excitation. The imaging transducer's performance was superior to our previous 9-MHz mechanical IVUS prototype. The therapy catheter transducer was driven by CW electrical power at 18.5 MHz, achieving temperature changes reaching +8°C at a depth of 2 mm in a human glioblastoma grown on the flank of a mouse with minimal transducer resistive heating of +2°C. Further hyperthermia trials showed that 9-MHz CW excitation produced temperature changes of +4.5°C at a depth of 12 mm-a sufficient temperature rise for our long-term goal of targeted, controlled drug release via thermosensitive liposomes for therapeutic treatment of 1-cm-diameter glioblastomas.

Delineation of atherosclerotic plaque using subharmonic imaging filtering techniques and a commercial intravascular ultrasound system.

The ability to delineate atherosclerotic plaque from the surrounding tissue using custom-developed subharmonic imaging (SHI) digital filtering techniques was investigated in vivo using a commercially available system. Atherosclerosis was induced in the aorta of two Watanabe Heritable Hyperlipidemic rabbits following which injections of an ultrasound contrast agent (UCA) Definity (Lantheus Medical Imaging, N Billerica, Massachusetts) were administered. Imaging was performed using a Galaxy intravascular ultrasound (IVUS) scanner (Boston Scientific, Natick, Massachusetts) equipped with an Atlantis® SR Pro Imaging Catheter (Boston Scientific). Four preliminary band-pass filters were designed to isolate the subharmonic signal (from surrounding tissue) and applied to the radio-frequency (RF) data. Preliminary filter performances were compared in terms of vessel-tissue contrast-to-tissue ratio (CTR) and visual examination. Based on preliminary results, a subharmonic adaptive filter and a stopband (SB) filter were designed and applied to the RF data. Images were classified as fundamental, SHI, and SB. Four readers performed qualitative analysis of 168 randomly selected images (across all three imaging modes). The images were scored for overall image quality, image noise, plaque visualization, and vessel lumen visualization. A Wilcoxon signed-rank test was used to compare the scores followed by intraclass correlation (ICC) evaluation. Quantitative analysis was performed by calculating the CTRs for the vessel-to-plaque and vessel-to-tissue (compared using a paired student's t test). Qualitative analysis showed SHI and SB to have significantly less image noise relative to the fundamental mode (p < 0.001). Fundamental mode scored significantly higher than SHI and SB for the remaining three categories. ICC showed mixed results among reader evaluation for delineation of plaque. However, quantitatively, SHI produced the best vessel-plaque CTR.

Cytological specimens obtained by endobronchial ultrasound-guided transbronchial needle aspiration: sample handling and role of rapid on-site evaluation.

Recently developed, endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) is a minimally invasive modality for mediastinal lymph node staging in lung cancer patients as well as for the diagnosis of mediastinal and hilar lymphadenopathy. It has been shown in systematic reviews and meta-analysis that a high diagnostic yield can be achieved with EBUS-TBNA for staging lung cancer. Though still not a standard of practice, this novel technology has attracted physicians and surgeons as an alternative modality to surgical biopsy for the assessment of the mediastinum. Standard cytology, thin layer preparations in liquid medium or cell blocks of cells obtained by EBUS-TBNA can be applicable not only for pathological diagnosis but also for further investigations such as immunohistochemistry and fluorescence in situ hybridization. In addition, samples obtained by EBUS-TBNA can also be used for molecular analysis. The key to a successful EBUS-TBNA is to understand the anatomy of the mediastinum as well as the basic steps of the procedure. Moreover, handling of the sample obtained by EBUS-TBNA is crucial for diagnosis since no amount of skill or interest of the interpreter can make up for a badly prepared sample. The goals of rapid on-site evaluation during EBUS-TBNA include determination of whether sampling of the target has been achieved and more importantly triage of samples to secondary investigations. This manuscript explains the detailed techniques of EBUS-TBNA to master this innovative procedure.

First in vivo use of a capacitive micromachined ultrasound transducer array-based imaging and ablation catheter.

OBJECTIVES: The primary objective was to test in vivo for the first time the general operation of a new multifunctional intracardiac echocardiography (ICE) catheter constructed with a microlinear capacitive micromachined ultrasound transducer (ML-CMUT) imaging array. Secondarily, we examined the compatibility of this catheter with electroanatomic mapping (EAM) guidance and also as a radiofrequency ablation (RFA) catheter. Preliminary thermal strain imaging (TSI)-derived temperature data were obtained from within the endocardium simultaneously during RFA to show the feasibility of direct ablation guidance procedures. METHODS: The new 9F forward-looking ICE catheter was constructed with 3 complementary technologies: a CMUT imaging array with a custom electronic array buffer, catheter surface electrodes for EAM guidance, and a special ablation tip, that permits simultaneous TSI and RFA. In vivo imaging studies of 5 anesthetized porcine models with 5 CMUT catheters were performed. RESULTS: The ML-CMUT ICE catheter provided high-resolution real-time wideband 2-dimensional (2D) images at greater than 8 MHz and is capable of both RFA and EAM guidance. Although the 24-element array aperture dimension is only 1.5 mm, the imaging depth of penetration is greater than 30 mm. The specially designed ultrasound-compatible metalized plastic tip allowed simultaneous imaging during ablation and direct acquisition of TSI data for tissue ablation temperatures. Postprocessing analysis showed a first-order correlation between TSI and temperature, permitting early development temperature-time relationships at specific myocardial ablation sites. CONCLUSIONS: Multifunctional forward-looking ML-CMUT ICE catheters, with simultaneous intracardiac guidance, ultrasound imaging, and RFA, may offer a new means to improve interventional ablation procedures.

Size of the transrectal ultrasound probe makes no difference in pain perception during TRUS-Bx under adequate local anesthesia.

INTRODUCTION AND OBJECTIVES: In the great majority of the cases, transrectal ultrasound guided prostate biopsy (TRUS-Bx) is the definitive step in the diagnosis of prostate cancer (CaP). Although this procedure is well tolerated by most patients, it can result in considerable discomfort that can effectively be overcome with local injection anesthesia. In this study, we evaluated the effect of the size (i.e., circumference) of the transrectal probe on pain during TRUS-Bx. MATERIAL AND METHODS: One hundred and seventy eligible patients who had elevated total prostate specific antigen (tPSA) and/or abnormal digital rectal examination (DRE) were included in this study. Patients (pts.) were divided into three TRUS-Bx groups; Group I: 60 pts. underwent TRUS-Bx with newer B-K Type 8808 probe (circumference 58 mm) under injectable periprostatic anesthesia, Group II: 60 pts. underwent TRUS-Bx with B-K Type 8551 probe (circumference 74 mm) under injectable periprostatic anesthesia, and Group III: 50 pts. underwent TRUS-Bx with B-K Type 8551 probe (circumference 74 mm) without local anesthesia. Periprostatic injection anesthesia was performed with 10 cc, 1% lidocaine (5 cc on each side) 10 min before TRUS-Bx. Pain was assessed using a 10-point modified visual analog scale (VAS) 15 min after the biopsy procedure. RESULTS: Three groups were homogeneous with respect to age and tPSA, and no statistically significant difference was observed in terms of mean biopsy duration between the 3 groups. Most of the patients experienced no pain to slight pain in Groups I and II, but 66% of the patients had more than moderate pain (VAS ≥ 5) in Group III with mean VAS score statistically higher than the other two groups (Group I vs. III, P = 0.0001; Group II vs. III, P = 0.0001). Mean VAS score was not statistically different between Group I and II (P = 0.126). No statistically significant difference in VAS pain perception was observed between different age categories within the Group I, II, and III. CONCLUSION: In the absence of injectable local anesthesia, larger probe (74 mm) results in much higher VAS pain perception than same size and smaller (58 mm) probe used under injectable local anesthesia. However, under injectable local anesthesia, the size (circumference) of the transrectal probe (58 mm vs. 74 mm) does not result in any different pain perception during TRUS-Bx.

Rotator cuff calcific tendinitis: does warm saline solution improve the short-term outcome of double-needle US-guided treatment?

PURPOSE: To determine whether saline temperature influences procedure performance and outcome in patients undergoing ultrasonography (US)-guided lavage for the treatment of rotator cuff calcific tendinitis (RCCT). MATERIALS AND METHODS: This study was approved by the institutional review board, and informed consent was obtained from all patients. From December 2009 to May 2011, 462 patients (191 men and 271 women; mean age, 39.7 years) with painful RCCT diagnosed at US were prospectively enrolled and randomized into two groups. Operators subjectively classified calcifications as hard, soft, or fluid according to their appearance at US. US-guided percutaneous treatment of RCCT (local anesthesia, double-needle lavage, intrabursal steroid injection) was performed with warm saline (42°C, 107°F) in 229 patients and with room-temperature saline in 233. Operators and patients were not blinded to saline temperature. The ease of calcium dissolution was subjectively scored (easy=1, intermediate=2, difficult=3). Procedure duration was recorded. Patient discomfort was assessed by using a visual analog scale (VAS). The occurrence of postprocedure bursitis was recorded. Statistical analyses were performed with Mann-Whitney U, χ2, and analysis of variance tests. RESULTS: Procedure duration was significantly shorter (P<.001) in patients treated with warm saline (mean, 576 seconds±121) than in those treated with room-temperature saline (mean, 777 seconds±151). Calcium dissolution was significantly easier in patients treated with warm saline (median score, 1) than in those treated with room-temperature saline (median score, 2). Subgroup analysis according to calcification appearance at US showed a significant difference between groups for both soft (P=.003) and hard (P<.001) calcifications. No overall significant differences were found for VAS score (warm saline group: baseline=8.9±0.6, 1 month=4.7±0.6, 2 months=4.0±0.7, 3 months=3.4±0.4, 1 year=3.0±0.7; room-temperature saline group: baseline=9.2±0.4, 1 month=4.5±0.7, 2 months=4.1±0.9, 3 months=3.1±0.7, 1 year=3.2±0.8; P=.491). Postprocedural bursitis was observed in eight patients in the warm saline group and 20 in the room-temperature saline group (P<.022). CONCLUSION: In the treatment of RCCT, warm saline appears to reduce procedure duration and improve calcification dissolution while reducing the frequency of postprocedural bursitis.

Dual-mode IVUS transducer for image-guided brain therapy: preliminary experiments.

In this study, we investigated the feasibility of using 3.5-Fr intravascular ultrasound (IVUS) catheters for minimally-invasive, image-guided hyperthermia treatment of tumors in the brain. Feasibility was demonstrated by: (1) retro-fitting a commercial 3.5-Fr IVUS catheter with a 5 × 0.5 × 0.22 mm PZT-4 transducer for 9-MHz imaging and (2) testing an identical transducer for therapy potential with 3.3-MHz continuous-wave excitation. The imaging transducer was compared with a 9-Fr, 9-MHz ICE catheter when visualizing the post-mortem ovine brain and was also used to attempt vascular access to an in vivo porcine brain. A net average electrical power input of 700 mW was applied to the therapy transducer, producing a temperature rise of +13.5°C at a depth of 1.5 mm in live brain tumor tissue in the mouse model. These results suggest that it may be feasible to combine the imaging and therapeutic capabilities into a single device as a clinically-viable instrument.

Invasive therapy for atrial fibrillation: recent developments in ablation, navigation and mapping technology.

The last decade has seen dramatic advances in cardiac electrophysiology, particularly in its application for treatment of atrial fibrillation and other tachyarrhythmias. In this paper, the authors review key new technologies now beginning to impact on contemporary practice that are taking its therapeutic potential to new levels of efficacy and safety.

Dual-mode IVUS catheter for intracranial image-guided hyperthermia: feasibility study.

In this study, we investigated the feasibility of modifying 3-Fr IVUS catheters in several designs to potentially achieve minimally-invasive, endovascular access for image-guided ultrasound hyperthermia treatment of tumors in the brain. Using a plane wave approximation, target frequencies of 8.7 and 3.5 MHz were considered optimal for heating at depths (tumor sizes) of 1 and 2.5 cm, respectively. First, a 3.5-Fr IVUS catheter with a 0.7-mm diameter transducer (30 MHz nominal frequency) was driven at 8.6 MHz. Second, for a low-frequency design, a 220-µm-thick, 0.35 x 0.35-mm PZT-4 transducer--driven at width-mode resonance of 3.85 MHz--replaced a 40-MHz element in a 3.5-Fr coronary imaging catheter. Third, a 5 x 0.5-mm PZT-4 transducer was evaluated as the largest aperture geometry possible for a flexible 3-Fr IVUS catheter. Beam plots and on-axis heating profiles were simulated for each aperture, and test transducers were fabricated. The electrical impedance, impulse response, frequency response, maximum intensity, and mechanical index were measured to assess performance. For the 5 x 0.5-mm transducer, this testing also included mechanically scanning and reconstructing an image of a 2.5-cm-diameter cyst phantom as a preliminary measure of imaging potential.

Heat-sensitive microbubbles for intraoperative assessment of cancer ablation margins.

A heat-sensitive microbubble (HSM) agent, comprising a core of liquid perfluorocarbon (PFC) compound and a shell of biodegradable poly lactic-co-glycolic acid (PLGA), was fabricated using an emulsion evaporation method. Optical microscopic imaging showed that heating the HSM suspension to 55 degrees C activated the HSMs for significant volumetric expansion. After placing a HSM-dispersed agar-agar gel phantom in a 55 degrees C water bath for 10 min, the phantom became ultrasonically hyperechoic due to the HSM expansion. In an ex vivo test, a porcine tissue sample was injected with the HSM suspension and placed in a 55 degrees C water bath for 10 min. US imaging clearly identified the hyperechoic regions resulted from the HSM activation. The hyperechoic regions in the tissue sample kept a strong US contrast for more than 1 h. In a simulated ablation process, a HSM-dispersed agar-agar gel phantom was ablated by a cylindrical heating element. US imaging accurately estimated the ablation margin propagation while thermographic imaging underestimated the ablation margin. Our experiments demonstrated that the HSM agent could be used as a novel contrast agent for intraoperative assessment of ablation margins in cancer thermal ablation therapies.

A family of intracardiac ultrasound imaging devices designed for guidance of electrophysiology ablation procedures.

Our Bioengineering Research Partnership grant, -High Frequency Ultrasound Arrays for Cardiac Imaging", including the individuals cited at the end of this paper - Douglas N. Stephens (UC Davis), Matthew O'Donnell (UW Seattle), Kai Thomenius (GE Global Research), Aaron M. Dentinger (GE Global Research), Douglas Wildes (GE Global Research), Peter Chen (St. Jude Medical), K. Kirk Shung (University of Southern California), Jonathan M. Cannata (University of Southern California), Butrus (Pierre) T. Khuri-Yakub (Stanford University), Omer Oralkan (Stanford University), Aman Mahajan (UCLA School of Medicine), Kalyanam Shivkumar (UCLA School of Medicine) and David J. Sahn (Oregon Health & Science University) - is in its sixth year of NIH funding, having proposed to develop a family of high frequency miniaturized forward and side-looking ultrasound imaging devices equipped with electrophysiology mapping and localization sensors and eventually to include a family of capactive micromachined ultrasonic transducer (cMUT) devices - a forward-looking cMUT MicroLinear array and a ring array capable of 3-dimensional imaging and a 5Fr lumen large enough to admit an electrode and ablation devices.

Dual-mode intracranial catheter integrating 3D ultrasound imaging and hyperthermia for neuro-oncology: feasibility study.

In this study, we investigated the feasibility of an intracranial catheter transducer with dual-mode capability of real-time 3D (RT3D) imaging and ultrasound hyperthermia, for application in the visualization and treatment of tumors in the brain. Feasibility is demonstrated in two ways: first by using a 50-element linear array transducer (17 mm x 3.1 mm aperture) operating at 4.4 MHz with our Volumetrics diagnostic scanner and custom, electrical impedance-matching circuits to achieve a temperature rise over 4 degrees C in excised pork muscle, and second, by designing and constructing a 12 Fr, integrated matrix and linear-array catheter transducer prototype for combined RT3D imaging and heating capability. This dual-mode catheter incorporated 153 matrix array elements and 11 linear array elements diced on a 0.2 mm pitch, with a total aperture size of 8.4 mm x 2.3 mm. This 3.64 MHz array achieved a 3.5 degrees C in vitro temperature rise at a 2 cm focal distance in tissue-mimicking material. The dual-mode catheter prototype was compared with a Siemens 10 Fr AcuNav catheter as a gold standard in experiments assessing image quality and therapeutic potential and both probes were used in an in vivo canine brain model to image anatomical structures and color Doppler blood flow and to attempt in vivo heating.

A prospective, randomized, controlled trial comparing ultrasound versus nerve stimulator guidance for interscalene block for ambulatory shoulder surgery for postoperative neurological symptoms.

BACKGROUND: Visualization with ultrasound during regional anesthesia may reduce the risk of intraneural injection and subsequent neurological symptoms but has not been formally assessed. Thus, we performed this randomized clinical trial comparing ultrasound versus nerve stimulator-guided interscalene blocks for shoulder arthroscopy to determine whether ultrasound could reduce the incidence of postoperative neurological symptoms. METHODS: Two hundred thirty patients were randomized to a standardized interscalene block with either ultrasound or nerve stimulator with a 5 cm, 22 g Stimuplex insulated needle with 1.5% mepivacaine with 1:300,000 epinephrine and NaCO3 (1 meq/10 mL). A standardized neurological assessment tool (questionnaire and physical examination) designed by a neurologist was administered before surgery (both components), at approximately 1 wk after surgery (questionnaire), and at approximately 4-6 weeks after surgery (both components). Diagnosis of postoperative neurological symptoms was determined by a neurologist blinded to block technique. RESULTS: Two hundred nineteen patients were evaluated. Use of ultrasound decreased the number of needle passes for block performance (1 vs 3, median, P < 0.001), enhanced motor block at the 5-min assessment (P = 0.04) but did not decrease block performance time (5 min for both). No patient required conversion to general anesthesia for failed block, and patient satisfaction was similar in both groups (96% nerve stimulator and 92% ultrasound). The incidence of postoperative neurological symptoms was similar at 1 wk follow-up with 11% (95% CI of 5%-17%) for nerve stimulator and 8% (95% CI of 3%-13%) for ultrasound and was similar at late follow-up with 7% (95% CI of 3%-12%) for nerve stimulator and 6% (95% CI of 2%-11%) for ultrasound. The severity of postoperative neurological symptoms was similar between groups with a median patient rating of moderate. Symptoms were primarily sensory and consisted of pain, tingling, or paresthesias. CONCLUSIONS: Ultrasound reduced the number of needle passes needed to perform interscalene block and enhanced motor block at the 5 min assessment; however, we did not observe significant differences in block failures, patient satisfaction or incidence, and severity of postoperative neurological symptoms.