Needle Direction Research Articles

Multiparametric MRI of the prostate with three functional techniques in patients with PSA elevation before initial TRUS-guided biopsy.

Multiparametric MRI (mp-MRI) of the prostate is increasingly being used for local staging and detection of recurrence of prostate cancer (PCA). In patients with elevated prostate-specific antigen (PSA), mp-MRI could provide information on the position of the cancer, allowing adjustments to be made to the needle depth and direction before repeat transrectal ultrasound (TRUS)-guided biopsy to ensure accurate sampling of lesions. The purpose of the prospective study was to evaluate mp-MRI of the prostate in patients with PSA elevation before initial TRUS-guided biopsy. mp-MRI was performed in 94 patients using a 1.5-T scanner (MAGNETOM Aera(®); Siemens Healthcare, Erlangen, Germany) and 16-channel phased-array body coil (Siemens Healthcare). T2 weighted images (T2WI), diffusion-weighted imaging (DWI), dynamic contrast-enhanced (DCE) MRI and MR spectroscopy were obtained. TRUS-guided random biopsies and additional targeted biopsies of suspicious MRI areas were performed. Additional targeted biopsies were obtained in 17 of 43 (40%) patients with PCA. 11 of 17 targeted biopsies contained PCA. 5 of 11 PCAs were diagnosed only by additional targeted biopsies. Sensitivity of mp-MRI in patients was 97.7% and specificity was 11.8%. mp-MRI was false negative in one patient. Sensitivity of mp-MRI in 207 lesions was 80.9% and specificity was 44.7%. In a logistic regression model, the apparent diffusion coefficient value was the only significant parameter to differentiate malignant and benign lesions. mp-MRI should be performed in patients with PSA elevation before initial TRUS-guided biopsy to allow additional targeted biopsies from suspicious areas of MRI. We recommend mp-MRI with T2WI, DWI, DCE MRI and MR spectroscopy. DWI as the most reliable technique should be used in every mp-MRI. DWI is the most reliable technique in mp-MRI of the prostate.

Electromagnetic needle tracking during simulated right internal jugular cannulation.

This study used three-dimensional information from Stealth navigation technology during simulated right internal jugular vein cannulation to define the initial needle trajectory taken when using three approaches: landmark (LM), short-axis (SAX) ultrasound and long-axis (LAX) ultrasound. Nineteen volunteers indicated the entry site and needle direction (track) they would use in performing right internal jugular vein cannulation by the three approaches. The likelihood of cannulation success, arterial puncture and needle direction were recorded. Volunteers were asked to assess the suitability of the simulation system for validity and educational benefit. The SAX track crossed the jugular vein more frequently than the LAX and LM tracks (SAX: 94%; LAX: 80%; LM: 47% [SAX versus LM, P <0.01]). The mean indicated needle direction in the coronal plane for LM, SAX and LAX were -4, 13 and 11 degrees, respectively. The track associated with the LAX technique would have entered the carotid artery by 16% of volunteers. At needle depths of over 40 mm, the track crossed the vertebral artery at the following rates (LM: 11%; SAX: 16%; LAX: 16%). The use of Stealth technology to provide three-dimensional feedback of the needle path taken during simulated right internal jugular cannulation was considered realistic (16/19) and of benefit for 18 of 19 (95%) respondents. The SAX track was associated with the highest likelihood of successful jugular cannulation and the lowest cross rate of the carotid artery. The simulation model using Stealth was considered to be valuable and realistic by participants despite some limitations.

Percutaneous transhepatic duodenostomy for a gastrectomy case with CT guidance and real-time visualization by an ultrasound and endoscopy

After gastrectomy, the remnant stomach, a small stomach behind the lateral segment of the liver, is thought to be a relative contraindication to receiving a percutaneous endoscopy-guided gastrostomy (PEG). We successfully performed a percutaneous duodenostomy in a case with remnant stomach. We used a transhepatic pull method with computed tomography (CT) guidance and real-time visualization by using ultrasound (US) and an endoscopy. The procedure was as follows: 1. Full stretching of the remnant stomach; 2. Insertion of a fine injection needle into the duodenal lumen through the lateral segment of the liver without an intrahepatic vascular and biliary injury using real-time visualization through US; 3. Confirmation of the location of the fine needle using abdominal CT, which showed the fine needle penetrating through the lateral segment and the duodenal lumen; 4. Insertion of the thick needle of the PEG kit just laterally of the fine needle; 5. Confirmation of the location of the thick needle using a repeated CT; 6. Endoscopic confirmation of the location of the two needles; 7. Changing the direction of the thick needle using guidance with endoscopy, inserting the thick needle into the duodenal lumen, and removing the fine needle; 8. Insertion of the guide wire through the thick needle; and 9. Placement of the PEG tube using the pull method. Using a real-time US scan, we detected the puncture of the anterior wall of the duodenum or stomach and avoided intrahepatic major vascular and biliary injuries.

Pencil-point needle bevel direction influences ED50 of isobaric ropivacaine with fentanyl in spinal anesthesia for cesarean delivery: a prospective, double-blind sequential allocation study

BackgroundThere is little evidence on the influence of bevel direction of a pencil-point needle on the median effective dose (ED50) of isobaric ropivacaine and fentanyl in spinal anesthesia for cesarean delivery. MethodsIn this prospective, double-blind, sequential allocation study, 82 parturients scheduled for elective cesarean delivery under combined spinal-epidural anesthesia were included. We sought to determine the median effective dose of intrathecal 0.75% isobaric ropivacaine plus fentanyl 15μg with two different bevel directions of a 26-gauge Whitacre needle using up-down sequential allocation. Parturients were randomly allocated to either Group Ce (needle aperture oriented in a cephalad direction) or Group Ca (aperture directed caudally). The initial dose was 0.75% ropivacaine 11.25mg plus fentanyl 15μg in both groups. Each dose was classified as effective if, after 15min and during the next 60min, there was inability to appreciate pin-prick as sharp at T4, a visual analogue pain score <2 and no requirement for an epidural rescue bolus. ResultsEighty patients were included in the analysis. The ED50 in group Ca was significantly higher (13.09mg, 95% CI 12.19–14.00) than in group Ce (10.10mg, 95% CI 9.54–10.65, P <0.001). ConclusionThe orientation of the distal aperture of a 26-gauge Whitacre needle during induction of spinal anesthesia for cesarean delivery influences the ED50 of 0.75% ropivacaine.

Super-long longitudinal magnetization needle generated by focusing an azimuthally polarized and phasemodulated beam

Based on the inverse Faraday effect, a super-long longitudinal magnetization needle can be induced by a transversely polarized needle-shaped electric field. This needle-shaped electric field can be obtained in the focal volume of the objective by focusing an azimuthally polarized vortex beam that is modulated both radially and azimuthally by a specifically designed annular phase filter. The numerical calculation shows that the full widths at half-maximums in longitudinal direction and in transverse direction of the magnetization needle are 28? and 0.27?. The corresponding needle aspect ratio of 103 is more than ten times larger than that of the magnetization needle fabricated by electron beam lithography.

Real-time ultrasound-guided infraorbital nerve block to treat trigeminal neuralgia using a high concentration of tetracaine dissolved in bupivacaine

BackgroundTrigeminal neuralgia is a neuropathic disorder characterized by episodes of intense pain in the face. Drug therapy is the first choice of treatment. However, in cases where drug therapy are contraindicated due to side effects, patients can get pain relief from lengthy neurosurgical procedures. Alternatively, a peripheral trigeminal nerve block can be easily performed in an outpatient setting. Therefore it is a useful treatment option for the acute paroxysmal period of TN in patients who cannot use drug therapy. We performed real-time ultrasound guidance for infraorbital nerve blocks in TN patients using a high concentration of tetracaine dissolved in bupivacaine. In this report, we examine the efficacy of our methods. Patients: As approved by the Institutional Review Board, the medical records in our hospital were queried retrospectively. Six patients with TN at the V2 area matched the study criteria. All patients could not continue drug therapy with carbamazepine due to side effects and they received an ultrasound-guided infraorbital nerve block with a high concentration of tetracaine dissolved in bupivacaine. MethodsThe patient was placed in the supine position and the patient's face was sterilized and draped. An ultrasound system with a 6–13MHz linear probe was used with a sterile cover. The probe was inserted into the horizontal plane of the cheek just beside the nose and was slid in the cranial direction to find the dimple of the infraorbital foramen. The 25G 25mm needle was inserted from the caudal side just across from the probe using an out-of-plane approach. To lead the needle tip to the foramen, needle direction was corrected with real-time ultrasound guidance. After the test block with lidocaine (2%, 0.5ml), a solution of tetracaine (20mg) dissolved in bupivacaine (0.5%, 0.5ml) was injected. During each injection, the spread of the agent around the nerve was confirmed using ultrasound images. ResultsTen blocks were performed for six patients. Immediately after the procedure, all 10 blocks produced analgesia and relieved the pain. In the three blocks, pain was experienced in a new trigger point outside of the infraorbital nerve region (around the back teeth) within a week after the block and pain were relieved using other treatment. Two patients developed small hematomas in the cheek but they disappeared in a week. All patients did not complain about other side effects including paraesthesia, hyperpathia, dysaesthesia, or double vision. Hypoaesthesia to touch and pain in the infraorbital region were observed in all blocks after 2 weeks. ConclusionsWe performed real-time ultrasound-guided infraorbital nerve block for TN with a high concentration of tetracaine dissolved in bupivacaine. Our method achieved a high success rate and there were only minor and transient side effects. Implications: Real-time ultrasound-guided infraorbital nerve block is one of the useful options to treat the acute paroxysmal period of TN at the infraorbital nerve area. Ultrasound-guided injections may become the standard practice for injecting peripheral trigeminal nerves. Using this high concentration of tetracaine as a neurolytic agent is effective and appears to have only minor side effects.

Polarization-dependent SERS effects of laser-generated sub-100 nm antenna structures

Sub-100 nm antenna arrays consisting of a star-like ridge or dome-like structures with needles in their centers are prepared in thin gold films on glass substrates using femtosecond laser pulses. The needles can be bent mechanically to be horizontally aligned to the substrate surface. Controlled variation of the pulse energy allows one to obtain nanostructures of different defined morphologies. These arrays of nanostructures are covered with a thin homogeneous layer of rhodamine molecules. Raman spectra using linearly polarized laser light of 632.8 nm are taken with the laser spot centered on individual nanostructures and at positions on the unstructured film. The average Raman enhancement within the laser spot focused onto a nanostructure is two orders of magnitude higher than on the unstructured film. The nanostructures with bent needles exhibit a polarization dependence of the SERS effect, i.e., typically the enhancement is larger by about a factor of two for excitation light polarized parallel to the needle direction than for the perpendicular case. The enhancement factor of the star-like ridge structures with needles is analyzed by the finite-element method, which agrees with the experiment. We show that the variation of the SERS activity of almost similar structures arises from the inherent randomness of the hot spots created in the fabrication process. Nevertheless, these antenna structures may be useful as elements in novel SERS devices as they can be accurately positioned on a device using a cheap fabrication process compatible with microfabrication technology.

3D modelling of β′′ in Al–Mg–Si: Towards an atomistic level ab initio based examination of a full precipitate enclosed in a host lattice

We extend a first principles based hierarchical multi-scale model scheme for describing a fully coherent precipitate in a host lattice to 3D simulations. As our test system, the needle-shaped main hardening Al–Mg–Si alloy precipitate β′′ is chosen. We show that computational costs do not impose practical limits on the modelling: the scheme can probe the full interface energy for physically sized and well isolated precipitates. Examining a series of energetically competitive bulk β′′ configurations, we highlight a series of results: (i) the scatter in the structural parameters for different β′′ configurations clearly exceeds experimental uncertainties also when interaction with the host lattice is taken into account. (ii) Structural and compositional β′′/Al interfaces generally coincide. This implies that precipitate stoichiometry is retained only for the two β′′ configurations with the lowest formation energy (compositions Mg5Al2Si4, Mg4Al3Si4). (iii) β′′–Mg4Al3Si4 emerges as a minimum energy configuration for large precipitates. Finally, (iv) more complete modelling, with precipitates surrounded by Al in all three dimensions, is expected to highlight a non-negligible influence of the precipitate misfit along the main growth (needle) direction.

Cannulation technique influences arteriovenous fistula and graft survival

Hemodialysis patient survival is dependent on the availability of a reliable vascular access. In clinical practice, procedures for vascular access cannulation vary from clinic to clinic. We investigated the impact of cannulation technique on arteriovenous fistula and graft survival. Based on an April 2009 cross-sectional survey of vascular access cannulation practices in 171 dialysis units, a cohort of patients with corresponding vascular access survival information was selected for follow-up ending March 2012. Of the 10,807 patients enrolled in the original survey, access survival data were available for 7058 patients from nine countries. Of these, 90.6% had an arteriovenous fistula and 9.4% arteriovenous graft. Access needling was by area technique for 65.8%, rope-ladder for 28.2%, and buttonhole for 6%. The most common direction of puncture was antegrade with bevel up (43.1%). A Cox regression model was applied, adjusted for within-country effects, and defining as events the need for creation of a new vascular access. Area cannulation was associated with a significantly higher risk of access failure than rope-ladder or buttonhole. Retrograde direction of the arterial needle with bevel down was also associated with an increased failure risk. Patient application of pressure during cannulation appeared more favorable for vascular access longevity than not applying pressure or using a tourniquet. The higher risk of failure associated with venous pressures under 100 or over 150 mm Hg should open a discussion on limits currently considered acceptable.

Investigating recurrent neural networks for OCT A-scan based tissue analysis.

Optical Coherence Tomography (OCT) has been proposed as a high resolution image modality to guide transbronchial biopsies. In this study we address the question, whether individual A-scans obtained in needle direction can contribute to the identification of pulmonary nodules. OCT A-scans from freshly resected human lung tissue specimen were recorded through a customized needle with an embedded optical fiber. Bidirectional Long Short Term Memory networks (BLSTMs) were trained on randomly distributed training and test sets of the acquired A-scans. Patient specific training and different pre-processing steps were evaluated. Classification rates from 67.5% up to 76% were archived for different training scenarios. Sensitivity and specificity were highest for a patient specific training with 0.87 and 0.85. Low pass filtering decreased the accuracy from 73.2% on a reference distribution to 62.2% for higher cutoff frequencies and to 56% for lower cutoff frequencies. The results indicate that a grey value based classification is feasible and may provide additional information for diagnosis and navigation. Furthermore, the experiments show patient specific signal properties and indicate that the lower and upper parts of the frequency spectrum contribute to the classification.

Optimizing Needle Direction During Transjugular Liver Biopsy Provides Superior Biopsy Specimens

Transjugular liver biopsy (TJLB) is commonly performed for staging of liver fibrosis and cirrhosis among patients with coagulopathy and/or ascites. We hypothesized that device orientation during needle firing influences hepatic tissue apposition with the specimen notch and specimen quality. Needle biopsies were performed in ex vivo bovine livers with specimen notch of the biopsy device oriented at cranial, caudal, or lateral directions with respect to the guiding metal cannula. Biopsy specimen length was measured and evaluated for fragmentation using light microscopy. In addition, a consecutive cohort of patients (n = 50) who underwent TJLB with random (n = 22) or caudal (n = 28) needle orientation was retrospectively reviewed. The number of needle passes was documented, and pathology specimen adequacy was graded using an ordinal scale. A total of 400 biopsies were performed (100 in each orientation) in ex vivo bovine livers. Longer specimens were obtained with caudal orientation of the needle specimen notch (p < 0.0001, ANOVA and Kruskal-Wallis tests). There was no difference in the degree of fragmentation. In the retrospective clinical study, specimen adequacy was significantly higher among patients in the caudal orientation group (p = 0.0002, Mann-Whitney U test). Caudal orientation of the needle specimen notch of the biopsy device during TJLB produces superior core biopsy specimens. This simple technical modification may assist in obtaining higher-quality biopsy specimens during TJLB.

Anatomical segmentectomy of the lung: tip of identifying the intersegmental plane

A pulmonary segmentectomy requires identification of the segmental planes, making it technically more difficult than a lobectomy. Therefore, we present a selective segmental-inflation technique using a butterfly needle. This paper discusses anatomical segmenectomy with special reference to identifying the intersegmental plane. Methods First, the lung is deflated and the pulmonary vessels to the involved segment are divided. The segmental bronchus is divided using a stapling device or ligation. Then, using a butterfly needle, oxygen (approximately 1 L/min.) is instilled into the targeted bronchus to inflate the involved segment, and the involved segment is severed and removed using electrocautery or a stapling device. The raw surface is covered with an absorbable sealing material to prevent air leaks. Results Fifty-three (M:F = 33:33) patients underwent anatomical segmentectomy with the selective segmental-inflation technique using a butterfly needle. Their median age was 64.9 years. The diseases were malignant lung disease in 52 patients and benign lung disease in 14. The surgical procedure was segmentectomy only in 60 and segmentectomy combined with lobectomy in six. The median operating time was 170 min; the blood loss was 82 g; and the postoperative stay was 8 days. The duration of chest tube drainage was 3 days. No major complication occurred. Conclusions In summary, anatomical segmentectomy was performed successfully with the selective segmental-inflation technique using a butterfly needle. Advantages: Surgeons can control every manipulation. No special device is needed; a butterfly needle is sufficient. It is useful regardless of the situation of proximal bronchus. Ultraselective air instillation into the subsegmental bronchus depends on the needle direction. Disadvantages: The proximal site of the targeted bronchus must be identified. Care is needed to avoid systemic air embolism.

Axillary Vein Puncture Without Contrast Venography for Pacemaker and Defibrillator Leads Implantation

Axillary vein puncture has been demonstrated to be an effective method for pacemaker and defibrillator leads implantation, without the complications encountered with the standard intrathoracic approach. Different techniques have been adopted for the cannulation of the axillary vein. We report our experience using the outer edge of the first rib below the inferior border of the clavicle as fluoroscopic landmark. A subcutaneous pocket is created 1-cm medially and parallel to the delto-pectoral groove and 2 cm below the clavicle. An 18-gauge needle from the upper border of the pocket is directed perpendicularly to the outer edge of the first rib just below the inferior border of the clavicle. If the vein is not entered, the needle is withdrawn and the puncture is repeated with slight variations of needle direction for a maximum of four to five times, then contrast-guided vein puncture is performed. Upon successful vein puncture, a guidewire is inserted and positioned in the superior vena cava. The remainder of the implantation is carried out in a routine manner. The axillary vein was successfully cannulated without venography in 172 of 182 consecutive patients (94.5%); the vein could not be found in 10 patients (5.5%): in these patients the vein was successfully cannulated after venography performance. No pneumothorax, hemothorax, or brachial plexus injury occurred. Our approach of axillary venipunture using fluoroscopic landmark, without contrast venography, is simple, safe, and effective.

Combination of High-Resolution Ultrasound-Guided Perivascular Regional Anesthesia of the Internal Carotid Artery and Intermediate Cervical Plexus Block for Carotid Surgery

All previously documented regional anesthesia procedures for carotid artery surgery routinely require additional local infiltration or systemic supplementation with opioids to achieve satisfactory analgesia because of the complex innervation of the surgical site. Here, we report a reliable ultrasound-guided anesthesia method for carotid artery surgery. High-resolution ultrasound-guided regional anesthesia using a 12.5-MHz linear ultrasound transducer was performed in 34 patients undergoing carotid endarterectomy. Anesthesia consisted of perivascular regional anesthesia of the internal carotid artery and intermediate cervical plexus block. The internal carotid artery and the nerves of the superficial cervical plexus were identified, and a needle was placed dorsal to the internal carotid artery and directed cranially to the carotid bifurcation under ultrasound visualization. After careful aspiration, local anesthetic was spread around the internal carotid artery and the carotid bifurcation. In the second step, local anesthetic was injected below the sternocleidomastoid muscle along the previously identified nerves of the intermediate cervical plexus. The necessity for intra-operative supplementation and the conversion rate to general anesthesia were recorded. Ultrasonic visualization of the region of interest was possible in all cases. Needle direction was successful in all cases. Three to five milliliters of 0.5% ropivacaine produced satisfactory spread around the carotid bifurcation. For intermediate cervical plexus block, 10 to 20 mL of 0.5% ropivacaine produced sufficient intra-operative analgesia. Conversion to general anesthesia because of an incomplete block was not necessary. Five cases required additional local infiltration with 1% prilocaine (2–6 mL) by the surgeon. Visualization with high-resolution ultrasound yields safe and accurate performance of the block. Because of the low rate of intra-operative supplementation, we conclude that the described ultrasound-guided perivascular anesthesia technique is effective for carotid artery surgery.

What Nephrologists Need to Know about Vascular Access Cannulation

This article describes cannulation events, especially problems, common and rare, minor and major, to aid the nephrologist (and mid-level providers e.g. nurse practitioner and physician's assistant) in decision-making to prevent or treat cannulation-related adverse outcomes. The usual management, potential outcomes, nephrologist intervention, and prevention are discussed and include: assessment of arteriovenous (AV) access and readiness for cannulation; initial cannulation of both arteriovenous fistulas and grafts; needle size and adequacy; needle direction and potential for recirculation; limited cannulation sites/buttonhole; pain and fear of pain; prevention of bleeding; management of infiltrations/extravasations; prevention and management of "one-site-itis"; prevention and management of infection. It concludes with the importance of the medical director as the leader of the continuous quality improvement (CQI) team in preventing/reducing cannulation-related adverse events.

Dört Farklı Supraklaviküler Blok Tekniğinde Plexus Brachialis Derinliği ile Demografik Veriler Arasındaki İlișkinin Değerlendirilmesi

Amaç: Aynı kadavra üzerinde dört farklı supraklaviküler blok tekniğini uygulayarak gerçekleștirdiğimiz bu çalıșmada, plexus brachialis’e ulașmak için gerekli olan iğne derinliğini ve bu parametre ile demografik veriler arasındaki ilișkiyi araștırmayı planladık. Gereç ve Yöntem: Bu araștırma, 10 adet kadavra üzerinde gerçekleștirildi. Diseksiyon tamamlandıktan sonra cilt tekrar eski konumuna getirilerek kadavranın bașına ve kollarına üzerinde çalıșılan tekniğe uygun pozisyon verildi. Kadavralarda 4 farklı supraklaviküler blok tekniği (Vongvises Dalens, Plumb-Bob ve İnter-SCM) uygulandı. Plexus brachialis’e ulașmak için gerekli olan iğne derinliği ölçüldü ve demografik veriler kaydedildi. Bulgular: İğne derinliğinin (Dalens tekniğinde ise en az) inter-SCM tekniğinde en fazla olduğu belirlendi. Plumb-Bob tekniği ile demografik veriler arasında korelasyon saptanmadı. Diğer tekniklerin tümünde, iğne derinliği ile kadavraların boy uzunluğu arasında korelasyon vardı. İğne derinliği ile kadavraların vücut ağırlıkları arasında korelasyon sadece inter-SCM tekniğinde tespit edildi. Sonuç: İğne derinliğinin (Dalens tekniğinde ise en az ) inter-SCM tekniği’nde en fazla, olduğu belirlendi. Erișkinlerde Dalens’in blok tekniği uygulanacağı zaman, iğne fazla ilerletildiği takdirde 1. interkostal aralıktan girilerek pnömotoraks gelișebileceği gözlendi. Vongvises tekniğinde cilde giriș yerinin yaklașık 1 cm altından girilerek, iğnenin masa düzlemine dik olacak șekilde antero-posterior yönde ilerletilmesiyle, plexus brachialis’in bașarılı bir șekilde bloke edilebileceği düșünüldü.

A different approach to the percutaneous nephrostomy by urologists

IntroductionPercutaneous nephrostomy (PCN) tube placement is generally performed in radiologic departments worldwide. However, there are a few urologist-directed studies about PCN performed with ultrasound guidance. Needle direction using a convex abdominal ultrasound probe might be difficult in unexperienced hands. In order to perform this procedure easily, we propose that a probe placed on flank or intercostal region and a long grooved needle director that never allows needle movement would be useful. We considered that a transrectal ultrasound (TRUS) probe was suitable to resolve this issue. Materials and methodFrom January 2007 to April 2011, a total of 113 percutaneous renal access (PRA) were performed using a TRUS probe in 102 patients, aged 20–84 years old. Because of the insufficient imaging capability of the TRUS probe in obese patients, with a body mass index (BMI) greater than 30kg/m2, these were excluded. Forty-two PRA were performed under local anesthesia and this group was named local anesthesia (LA) group. Seventy-one PRA were performed for nephrostomy insertion under local anesthesia supplemented by deep sedation and this cluster was named deep sedation (DS) group. ResultsTargeted calyx puncture and guide wire placement was performed in all patients (100%) but success rate of tube insertion in each group was different. Successful PCN insertion rate was 69.1% (29 of 42 cases) in LA group and 95.8% (68 of 71 cases) in DS group. No major vascular injury and/or adjacent organ injury to bowel, liver, spleen or lung was seen in any patient. ConclusionGuidance of TRUS probe, deep sedation, and modified dilators may offer a high success rate to the urologists with little experience in PCN insertion which they would find it difficult to perform.

Directable needle guide: efficacy for image-guided percutaneous interventions.

Diagnostic and therapeutic image-guided percutaneous interventions have become increasingly important in the clinical management of various conditions. Though precise needle placement via a safe route is essential for successful percutaneous interventions, it is often difficult in cases of deeply situated, small lesions. The present paper describes the efficacy of the directable needle guide (DNG), which allows manipulation of the direction of a fine needle within organs. The DNG was used in patients for needle biopsy of hepatic (n = 26) and splenic (n = 1) lesions and for percutaneous ethanol injection therapy for liver tumors (n = 33) under sonographic or computed tomography guidance. The DNG enabled the direction of a 21- or 22-gauge needle to be successfully changed during needle advancement in all cases, allowing adjustment of the location of the needle tip or needle access root to avoid vessels, the gallbladder, and the lungs. We conclude that DNG increases the safety and ease of percutaneous interventions.

Fluctuating gravity of Earth’s core

For centuries, we have known that Earth’s magnetic field varies with time. Edmond Halley (better known for his eponymous recurring comet) first recognized this time variation of magnetic compass needle direction and even offered a remarkable theory that required an intervening fluid between Earth’s solid outer shell and a hypothesized innermost solid core (1). For decades, consensus has emerged for an explanation of this time variation that depends on the dynamics of Earth’s liquid metallic outer core. In this dynamo theory (2), the fluid motions responsible for field regeneration arise because of density differences within the fluid, much as density and pressure differences in Earth’s atmosphere or ocean can drive circulation and vertical motions in those regions of Earth. Density differences necessarily imply changes in Earth’s gravity field, so it is only a small step in logic to imagine that there could be changes in the gravity field that correlate with changes in the magnetic field, with both changes arising from fluid flow in the core. In PNAS, Mandea et al. (3) claim to have found possible evidence for such a correlation on a time scale of a few years to a decade.

Assessment of a real-time ultrasound-guided spinal technique using SonixGPS™ in human cadavers

To the Editor, With improvements in ultrasound (US) technology, there is significant momentum to develop and apply a clinically viable real-time ultrasound-guided neuraxial technique. Previously described methods using in-plane approaches have been hindered by poor needle visibility due to the steep needle insertion angles required for neuraxial blockade, the acoustic shadows of the bony spinal structures, and the fine gauge of spinal needles. We recently used a cadaver model to develop a new technique involving single-operator real-time US-guided needlethrough-needle spinal injection. Two unembalmed cadavers, one female and one male, were obtained in accordance with the University of British Columbia Clinical Research Ethics Board. A SonixTablet ultrasound system (Ultrasonix, Richmond, BC, Canada) was used in an out-of-plane approach with either a 5-14 MHz SonixGPS enabled linear transducer or a 2-5 MHz convex transducer, depending on the depth to the neuraxial space. The SonixGPS system (Ultrasonix, Richmond, BC, Canada) uses sensors in the needle and ultrasound probe to track the needle position relative to the ultrasound image. Predicted trajectory and location of the needle tip are displayed digitally in real-time and overlaid on the ultrasound image. Two anesthesiologists with experience using the SonixGPS system for regional anesthesia used the technology for the first time for a neuraxial technique. With the cadavers in a prone position, the anesthesiologists performed 16 injections between T2/3 and L4/5. For each simulated spinal block, they obtained an optimal sonographic view of the laminae and neuraxial structures in a paramedian oblique sagittal plane. A SonixGPS enabled 8-cm 19G introducer needle was inserted out-of-plane and directed with the needle guidance technology towards the ligamentum flavum. Once the tip was positioned near the ligamentum, the inner stylet containing the needle sensor was removed, and a 12-cm 22G spinal needle was inserted through the introducer in a needle-through-needle technique. The spinal needle was then advanced to the neuraxial space and coloured acrylic dye was injected through the needle (see Figure). The spinal needles were left in situ to guide subsequent dissection by a blinded anatomist. All 16 spinal needles and injections were found to be at the target upon dissection. The anatomist confirmed presence of dye in the neuraxial space in 100% of attempts, and there was no dye found in the tissues outside the neuraxial space. There was excellent visualization of spinal sonoanatomy in 63% of attempts and good visualization in the remainder. The SonixGPS system allowed prediction of the appropriate needle direction to target the neuraxial space in 100% of attempts. Mean (standard deviation) depth to the neuraxial space on US was 3.21 (0.71) cm and 4.74 (0.59) cm for the female and male cadavers, respectively. Importantly, all 16 attempts required only a single skin puncture with minimal requirement for redirection. SonixGPS needle guidance technology facilitated real-time ultrasound-guided neuraxial injection in cadavers with accuracy and reproducibility. Our out-of-plane approach enabled the needle to be inserted in a traditional paramedian trajectory, and SonixGPS needle guidance technology overcame problems of poor visibility of the needle tip at steep insertion angles. Limitations of the cadaver included the immobile spine and a lack of cerebrospinal fluid. Given that the proceduralists were S. Brinkmann, FANZCA (&) R. Tang, FRCPC H. Vaghadia, FRCPC A. Sawka, FRCPC Vancouver General Hospital, Vancouver, BC, Canada