Accuracy Of Electrode Placement Research Articles

The relative accuracies of ECG precordial lead waveforms derived from EASI leads and those acquired from paramedic applied standard leads

Accurate precordial electrode placement can be difficult in emergency situations leading either to loss of time or diminished accuracy. A possible solution is the quasi-orthogonal EASI lead system, with only five electrodes and easily defined landmarks to provide a derived 12-lead electrocardiogram (ECG). The purpose of this study was to test the hypothesis that precordial waveforms in EASI-derived ECGs have no greater deviation from those in gold standard ECGs, than do the precordial waveforms in paramedic acquired standard ECGs. Twenty paramedics applied the standard precordial electrodes employing the routine procedure. A certified ECG technician applied the 6 standard precordial electrodes in their correct gold standard positions, and the EASI electrodes. 12-lead ECGs were obtained from the paramedics’ standard leads, and derived from the EASI leads, for comparison with the gold standard ECG. In each precordial lead recording, 6 computer-measured QRS-T waveform parameters were considered. Differences between ΔEASI-gold standard versus Δparamedic-gold standard were calculated for every waveform in every lead resulting in 720 comparisons. EASI and paramedic results were “equally accurate” in 47%, the paramedic was more accurate in 31%, and EASI was more accurate in the remaining 22%. The differences from gold standard recording of precordial waveforms in ECGs derived from the EASI leads and those acquired via paramedic-applied standard electrodes are similar. The results suggest that the EASI lead system may provide an alternative to the standard ECG precordial leads to facilitate data acquisition and possibly save valuable time in emergency situations.

Evaluation of Neuronavigation in Lesional and Non-Lesional Epilepsy Surgery

Objective: For many patients, surgery for intractable epilepsy provides not only freedom or substantial relief from seizures, but also functional improvement and increased quality of life. Precise intraoperative localization of the underlying structural and functional processes is crucial in this regard. The aim of this study was to clinically evaluate whether neuronavigation leads to an improvement in the precision and safety of epilepsy surgery. In this paper, we also attempt to assess the navigation workstation as a platform for the integration of multimodal information (multimodal information guidance).Patients: Out of a series of 223 epilepsy surgery procedures, 140 were performed with the aid of neuronavigation. Patient and surgical data were prospectively collected.Methods: We used the neuronavigation device as a common platform to merge complementary information modalities. Correlation of anatomic and structural details with functional information contributed to the surgical script in non-lesional and localization-related epilepsy surgery. At least two different information modalities contributed to planning and surgical guidance in every patient. Immediately following the operative procedure, the surgeon answered a set of questions on the reasons for the application of neuronavigation, and the efficiency and safety of navigation. Detailed analysis of the location of the operative procedure, histopathological findings and outcome was performed.Results: The main benefits of neuronavigation in epilepsy surgery were precision of targeting even in small and deep-seated targets, safe manipulation in critical brain areas, accurate placement of electrodes, and correlation of electro-clinical information modalities with underlying structures. Furthermore, navigation provided individual tailoring of craniotomy and corticotomy. It was less reliable for verification of resection boundaries in the case of underlying glioma. Neuronavigational localization and its combination with image fusion and functional investigations greatly improved discussion within the epilepsy surgery team.Conclusion: The neuronavigation concept proved its value in epilepsy surgery by linking anatomic, pathologic and functional data of the individual patient. Enhanced by the integration of multimodal information, neuronavigation significantly improved the available treatment options.

An introduction to cardiac monitoring and rhythm interpretation

ABSTRACTThis article is the first in a series which will explore the identification and management of cardiac arrhythmias within the peri-operative care setting. To improve patient safety, the number of patients who are monitored within the recovery room is rising, whilst cardiac monitoring remains a fundamental requirement for patient care during the anaesthetic phase. Therefore, the role of the peri-operative care nurse requires an ability to interpret cardiac arrhythmias and to subsequently instigate the appropriate management.The purpose of this preliminary article is to establish the basic principles that underpin the identification and management of arrhythmias. Cardiac physiology is reviewed and then applied to the derivation of the waveforms of the normal ECG. The article continues with a summary of accurate electrode placement and some tips for troubleshooting in the presence of ‘artifact’. A systematic analysis tool, which can be easily applied to clinical practice, completes the article.

Insertion of depth electrodes with or without subdural grids using frameless stereotactic guidance systems -- technique and outcome

Over recent years frameless stereotactic systems have begun replacing framed systems for many neurosurgical procedures. However, little has been published regarding the use of these systems to guide intracranial electrode implantation for epilepsy surgery patients. Here we report our experience utilising such a system to insert depth electrodes and subdural grid electrodes. The SteathStation Image-Guided System TM (SSIGS) (Sofamor Danek, Memphis TN.) was used to insert bilateral depth electrodes in 13 patients, of whom 5 also underwent the insertion of subdural grids or strip electrodes. Initially, a surgical plan based on an entry and target point on axial and sagittal images was performed for the insertion of electrodes. Navigational views, using three-planar images, were then performed to determine which structures the electrodes would pass through to be correctly placed in the amygdala and hippocampus. The correct site of electrode implantation was confirmed post-operatively by spiral CT scans in 4 patients (which were then co-registered to the preimplantation MRI using a surface matching technique) and the other 9 patients by post-implantation MRI. The SSIGS was found to have a mean registration error of 2.0 mm (range 1.8-2.5) in 10 cases; in the 3 cases where the error was greater than 2.5 mm a surfacemerge technique was used with a mean error 0.9 (0.8-1.00). The post-implantation MRI or CT-MRI co-registration confirmed an accurate electrode placement in the mesial temporal region in all cases. Seizure onset lateralisation was achieved in 11 patients, all of whom went onto formal resections based on these results. The only long-term complication was a case of osteomyelitis which required removal of the bone flap. 73% of patients had an excellent seizure outcome. Frameless stereotactic systems can be safely used to intracranial electrodes, avoid the disadvantages of the framed system and have the added advantage of the surgeon being able to visualise the trajectory and to adjust this to avoid vital structures. As well they eliminate surgical obstruction to the insertion of subdural grids at the same operation, which may be caused by a framed system.

Pitfalls of intramuscular electromyographic recordings from the human costal diaphragm

Objective: Techniques for intramuscular recordings from the costal diaphragm have been described. This report describes procedures to assist with precise placement of these electrodes using ultrasound imaging and describes several sources of error that must be excluded when interpreting recordings made with intramuscular electrodes.Methods: Fine-wire electrodes were inserted into the left costal diaphragm under the guidance of ultrasound imaging in 17 healthy volunteers. Various respiratory maneuvers were performed to confirm the accuracy of the electromyographic (EMG) recordings and the electrode placement was confirmed with intercostal nerve blocks in one subject.Results: EMG recordings can be made from the costal diaphragm. However, despite precise electrode placement and use of intramuscular electrodes with small receptive areas, the EMG recording could be contaminated by cross-talk (discrete motor unit activity) from the adjacent internal intercostal muscle and from movement of the electrode relative to the muscle fibers during breathing. Furthermore, it is necessary to distinguish between expiratory intercostal muscle activity and units in the diaphragm that discharge tonically throughout expiration.Conclusions: While ultrasound guidance of intramuscular electrode insertion can assist with accurate electrode placement in the diaphragm, confirmation of the stability of the recording and absence of cross-talk is critical to avoid misinterpretation of diaphragm function.

In Vivo Results with a New Device for Ultrasonic Monitoring of Pig Skin Cryosurgery: The Echographic Cryoprobe

One of the main difficulties encountered in cryosurgery is the uncertainty in the extent and depth of the tissue effectively treated during the freezing process. The objective of this study was to evaluate in vivo ultrasonic control of skin cryosurgery using a new echographic cryoprobe. An echographic cryoprobe, developed specifically for dermatology applications, combines a high-frequency (20 MHz) miniature ultrasonic transducer and a N2O-driven closed cryoprobe. Knowledge of the ultrasound velocity of frozen skin is a prerequisite for monitoring the iceball formation kinetics. Therefore, in a first study, we estimated the ultrasound velocity of frozen skin specimens. In a second step, the operation of the echographic cryoprobe was assessed, under in vivo conditions similar to those used in human therapeutics, on normal skin of three female "Large-White" pigs under anesthesia. The mean value of ultrasound velocity of frozen skin obtained by pooling the data from all the skin specimens included in this study was 2865 +/- 170 m per s. The average rates of growth (10(-2) mm per s) of the iceballs were found to be 12.2 +/- 1.0 (pig 1), 9.0 +/- 1.0 (pig 2), and 8.4 +/- 0.9 (pig 3). The echographic cryoprobe had a built-in high-frequency ultrasonic transducer that served two functions. It enabled in vivo real-time monitoring of depth penetration of the iceball and it gave important feedback to the operator or to the console relating to the rate of growth of the iceball. Automatic (i.e., operator-independent) detection of the echo signal from the freezing front and calculation of the depth penetration of the iceball was possible.

New electrode system for rapid whole-body and segmental bioimpedance assessment.

Skeletal muscle is a clinically important body composition component which at present is difficult to quantify in vivo. Previous studies suggest that measured appendicular resistance at 50 kHz can be used to predict extremity skeletal muscle mass, although accurate technician placement of multiple gel electrodes is required. In the present study we developed a new bioimpedance analysis (BIA) electrode stand designed for rapid whole-body and segmental resistance and reactance measurements. The new system incorporates stainless steel hand and foot contact electrodes in place of gel electrodes and employs a previously reported lead placement algorithm for deriving extremity resistances without the need for placing conventional proximal limb gel electrodes. This report describes the new electrode system's design and examines the relationships between contact and gel electrode-measured resistance and between appendicular resistance measured with the recently reported lead placement algorithm and conventionally placed segmental electrodes. Results in healthy adults demonstrate high correlations between contact and gel electrodes (e.g., hand-to-hand, N = 12, r = 0.994, P < 0.001) and between segmental resistance measured by the recently reported approach and conventionally-measured segmental resistance (e.g., right arm, N = 13; r = 0.997, P < 0.001). These results strongly support the validity of the new electrode system's resistance measurements and suggests the feasibility of developing a BIA system for rapidly measuring extremity skeletal muscle mass.

Split cannula method for accurate placement of an electrode for deep brain stimulation: technical note.

We describe a "split cannula method" for accurate placement of a deep brain stimulation electrode. This method eliminates the risk of displacement of the electrode when withdrawing the outer guide cannula. A separate short guide cannula is covered over the distal part of a long cannula for microrecording or macrostimulation. After confirmation of the stimulation point, the short cannula is fixed with an accessory-holding device and the long cannula is pulled out. The electrode for deep brain stimulation is inserted through the short cannula. Because this cannula is much shorter than the electrode, securing the stimulation electrode at any withdrawal stage of the outer guide cannula is always possible. With this simple method, we experienced no displacement of the stimulation point during stereotactic insertion of a deep brain stimulation electrode. This method can be easily adapted to any stereotactic frame.

The nurse's role in continuous dysrhythmia monitoring.

One of the areas of clinical management where nurses have the most diagnostic influence is cardiac rhythm monitoring and dysrhythmia detection. The critical care nurse must recognize that continuous monitoring is a nursing responsibility, and competence in this skill must be assured. It is essential that nurses understand the significance of accurate electrode placement in obtaining a specific monitoring lead. In addition, the nurse must use current research in determining which monitoring lead is most appropriate for the patient requiring cardiac monitoring in the critical care environment. The author reviews the current research on continuous bedside monitoring and lead selection, examines why nurses continue to make less than optimal lead selection decisions, and offers recommendations to improve the consistency with which patients are accurately monitored.

Stereotaxic lesions of the hippocampus in monkeys: determination of surgical coordinates and analysis of lesions using magnetic resonance imaging

A technique is described for producing accurate stereotaxic lesions of the hippocampus in monkeys. This technique overcomes the problem that the size and shape of the brain can vary considerably from monkey to monkey. Magnetic resonance imaging (MRI) is used to create an individual brain atlas for each monkey. The atlas is then used to derive coordinates for making stereotaxic radio frequency lesions of the hippocampus. There are two key features of this procedure. First, a specially-designed, acrylic, stereotaxic headholder was constructed that could be used safely with the MR magnet. Second, small glass beads, anchored to the skull of the monkey, served as common landmarks from which lesion coordinates were determined in the MR images and then again in neurosurgery. MRI techniques are also described for determining the extent of tissue damage postoperatively. This technique could also prove useful in other areas of neuroscience research that depend on accurate stereotaxic placement of electrodes (e.g., electrophysiological studies and neuroanatomic tracing studies).

The effect of electrode position on flash visual evoked potentials in the newborn

We examined how changes in electrode position affected the visual evoked potential in 74 high-risk newborns using a multiple electrode technique. The variation in the visual evoked potential across the occiput was documented. Visual evoked potentials that were visible at one occipital electrode position were absent at a different electrode position in 21 of 87 recordings (24%). Changes of greater than 20 msec between electrodes in latency of waves P1 or N2 occurred in 34% and 29% of recordings, respectively. The amplitude of response varied by a factor of 2.36 between mid occipital and lateral occipital electrodes. The results demonstrated that large changes in morphologic characteristics, latency, and amplitude in the visual evoked potential of the newborn result from small changes in the position of recording electrodes. These findings underscored the importance of electrode position and accurate electrode placement. Our observations also indicated that recordings from a single electrode are inadequate in providing an accurate representation of the neonatal visual evoked potential.

A new surface electrode for recording from the posterior cricoarytenoid muscle.

A new pharyngeal surface electrode for recording posterior cricoarytenoid muscle activity through the hypopharyngeal mucosa has been evaluated. The electrode was passed through one nasal passage into the hypopharynx. Correct electrode location was verified by increased activity during inhalation, with decreased activity during phonation. The procedure was evaluated in 45 subjects, 10 normal speakers and 35 patients with dysphonia. Accurate recordings were obtained in 25 subjects (56%). Problems encountered were lack of pharyngeal descent, electrode dysfunction, and signal interference due to phonatory vibration or interarytenoid activity. Signal validity was evaluated in four normal speakers with accurate electrode placement. Significant (p less than or equal to 0.001) increases in PCA activity occurred during tasks requiring vocal fold abduction. The electrode proved to be a useful, noninvasive clinical tool for recording PCA activity in some patients.

Stereotactic implantation of deep brain electrodes using computed tomography

The selection of intracranial targets for stereotactic functional neurosurgical procedures traditionally has relied on information derived from pooled brain atlases and supplemented by contrast encephalographic or angiographic data from the individual patient. The integration of stereotaxy with computed tomography (CT) has permitted direct identification of intracranial targets based on multiplanar reformatted CT images from each individual patient. Four patients underwent the CT stereotactic implantation of a single deep brain electrode for the control of chronic pain (two cases) or of multiple depth electrodes for long term electroencephalographic recordings in the management of seizure disorders (two cases). In all patients, accurate and precise electrode placement was achieved from CT images alone. The use of CT permitted detailed anatomical stereotactic study of each patient's brain, the preplotting of electrode trajectories before probe insertion, and the rapid confirmation of precise electrode placement. Intraoperative contrast encephalography was not necessary. Functional neurosurgery was performed successfully and advantageously using CT stereotactic technique alone (Neurosurgery 13:280-286, 1983)

Stereotactic implantation of deep brain electrodes using computed tomography.

The selection of intracranial targets for stereotactic functional neurosurgical procedures traditionally has relied on information derived from pooled brain atlases and supplemented by contrast encephalographic or angiographic data from the individual patient. The integration of stereotaxy with computed tomography (CT) has permitted direct identification of intracranial targets based on multiplanar reformatted CT images from each individual patient. Four patients underwent the CT stereotactic implantation of a single deep brain electrode for the control of chronic pain (two cases) or of multiple depth electrodes for long term electroencephalographic recordings in the management of seizure disorders (two cases). In all patients, accurate and precise electrode placement was achieved from CT images alone. The use of CT permitted detailed anatomical stereotactic study of each patient's brain, the preplotting of electrode trajectories before probe insertion, and the rapid confirmation of precise electrode placement. Intraoperative contrast encephalography was not necessary. Functional neurosurgery was performed successfully and advantageously using CT stereotactic technique alone.

Reflectance of rat brain structures mapped by an optical fiber technique

A method to detect differences in reflectance as a pair of glass fibers is advanced through various brain structures at a constant speed is described. The system has been used to develop a technique for accurate and easy placement of electrodes or cannulae into a limited brain region. The probe consisted of two thin (50 μm in diameter) glass optic fibers. A 5 W lamp was used to transmit light down one of these fibers. The relative intensity of light reflected from brain tissue into the other optic fiber was monitored with a photomultiplier and ink-writing recorder. Different brain structures were shown to vary in the amount of reflectance, with white matter having much higher reflectance than gray matter. It was demonstrated in a total of 239 penetrations that the patterns of successive changes in the reflected light response, as the probe was lowered into the brain, was characteristic for each frontal plane. The probe may additionally be itself used as an electrode if plated with silver.

A simple, multi-purpose animal preparation for use in a psychobiology laboratory course

Rats chronically prepared with single, bipolar electrodes in caudal midbrain central gray matter can be used in successive weeks to demonstrate to laboratory course students: sensory evoked potentials in anesthetized and unanesthetized preparations; self-stimulation and/or escape; and stimulationproduced analgesia to peripheral pain. The preparation and procedures are simple, and accuracy in electrode placement is enhanced by the proximity of this structure to stereotaxic zero. Using the same animal repetitively minimizes time spent in surgical preparation and post-surgical recovery. The central gray matter is a relatively unexplored region, and studying it can lead to original observations.

Outlining the cervical spinal cord with tantalum powder: application to percutaneous cordotomy. Technical note.

✓ Powdered tantalum introduced into the subarachnoid space at C-2 clearly outlines the anterior aspect of the cord and dentate ligaments. Accurate electrode placement for percutaneous intramedullary cordotomy is made easier by the presence of a radiopaque target.

A computer-controlled stereotaxic system.

The stereotaxic technique serves as an invaluable tool for the reliable and accurate placement of electrodes in living brain tissue. By placing the stereotaxic device under computer control an entirely new set of operational procedures is established which enhances and enriches the basic capabilities of the stereotaxic technique. The system consists of a number of basic programs which provide for positioning of the electrode, executing the particular experiment and reviewing the data. Programs are available which allow the experimenter to position the electrode at coordinates typed in via an on-line keyboard. One program allows the investigator to specify multiple points at once. The operator merely fills in a simple format displayed on the oscilloscope that defines the geometry of the electrode path. These geometries include points, lines, planes, and volumes. The system successively positions the electrode at all points explicitly and implicitly specified by the format and, at each intermediate point, executes the experimenter's specially written program. The computer presents a display to the investigator after executing his program (for example for stimulating and storing the resultant averaged evoked potentials) at each of those points. A comment may be entered by the experimenter that remains a permanent part of the data set (electrode position-comment-evoked potentials) stored on tape. The data sets may be recalled for review at anytime.

Experimental mutism in dogs.

Reports of experimental mutism in the literature have been confined chiefly to investigations in which cats were used as the experimental animal. 1-7 With one exception, 7 the lesion responsible for this phenomenon has been reported to be in the region of the periaqueductal gray matter. In 1944, Bailey and Davis 8 reported on similar lesions in the monkey, but no comment appears in their article as to whether or not the animals were mute. Although mutism has been reported in humans, 9-15 the individuals described were different from the above experimental animals as regards the location of pathologic processes and type and magnitude of neurologic deficits. Accordingly, the present investigations were undertaken to discover if lesions similar to those in the cat would result in mutism in another species, specifically the dog. Until recently, the use of dogs in experiments involving the accurate placement of lesions or electrodes has

A method for accurate placement of electrodes in the hypothalamus of the dog

A method for accurate placement of electrodes in the hypothalamus of the dog