High-Resolution Spatiotemporal Quantification of Intestinal Motility With Free-Form Deformation.

OBJECTIVE: To develop a method to quantify strain fields from in vivo intestinal motility recordings that mitigate accumulation of tracking error. METHODS: The deforming geometry of the intestine in video sequences was modeled by a biquadratic B-spline mesh. Green-Lagrange strain fields were computed to quantify the surface deformations. A nonlinear optimization scheme was applied to mitigate the accumulation of tracking error associated with image registration. RESULTS: The optimization scheme maintained the RMS strain error under 1% and reduced the rate of strain error by 97% during synthetic tests. The algorithm was applied to map 64 segmental, 12 longitudinal, and 23 propagating circular contractions in the jejunum. Coordinated activity of the two muscle layers could be identified and the strain fields were able to map and quantify the anisotropic contractions of the intestine. Frequency and velocity were also quantified, from which two types of propagating circular contractions were identified: (i) [Formula: see text] strain contractions that originated spontaneously and propagated at [Formula: see text] mm/s in two pigs, and (ii) cyclic propagating contractions of [Formula: see text] strain occurred at [Formula: see text] cpm and propagated at [Formula: see text] mm/s in a rabbit. CONCLUSION: The algorithm simultaneously mapped the circular, longitudinal activity of the intestine with high spatial resolution and quantified anisotropic contractions and relaxations. SIGNIFICANCE: The proposed algorithm can now be used to define the interactions of muscle layers during motility patterns. It can be integrated with high-resolution bioelectrical recordings to investigate the regulatory mechanisms of motility.

The influence of interstitial cells of Cajal loss and aging on slow wave conduction velocity in the human stomach.

Loss of interstitial cells of Cajal (ICC) has been associated with gastric dysfunction and is also observed during normal aging at ~13% reduction per decade. The impact of ICC loss on gastric slow wave conduction velocity is currently undefined. This study correlated human gastric slow wave velocity with ICC loss and aging. High-resolution gastric slow wave mapping data were screened from a database of 42 patients with severe gastric dysfunction (n = 20) and controls (n = 22). Correlations were performed between corpus slow wave conduction parameters (frequency, velocity, and amplitude) and corpus ICC counts in patients, and with age in controls. Physiological parameters were further integrated into computational models of gastric mixing. Patients: ICC count demonstrated a negative correlation with slow wave velocity in the corpus (i.e., higher velocities with reduced ICC; r2  = .55; p = .03). ICC count did not correlate with extracellular slow wave amplitude (p = .12) or frequency (p = .84). Aging: Age was positively correlated with slow wave velocity in the corpus (range: 25-74 years; r2  = .32; p = .02). Age did not correlate with extracellular slow wave amplitude (p = .40) or frequency (p = .34). Computational simulations demonstrated that the gastric emptying rate would increase at higher slow wave velocities. ICC loss and aging are associated with a higher slow wave velocity. The reason for these relationships is unexplained and merit further investigation. Increased slow wave velocity may modulate gastric emptying higher, although in gastroparesis other pathological factors must dominate to prevent emptying.

A V-Net Based Deep Learning Model for Segmentation and Classification of Histological Images of Gastric Ablation.

Gastric motility disorders are associated with bioelectrical abnormalities in the stomach. Recently, gastric ablation has emerged as a potential therapy to correct gastric dysrhythmias. However, the tissue-level effects of gastric ablation have not yet been evaluated. In this study, radiofrequency ablation was performed in vivo in pigs (n=7) at temperature-control mode (55-80°C, 5-10 s per point). The tissue was excised from the ablation site and routine H&E staining protocol was performed. In order to assess tissue damage, we developed an automated technique using a fully convolutional neural network to segment healthy tissue and ablated lesion sites within the muscle and mucosa layers of the stomach. The tissue segmentation achieved an overall Dice score accuracy of 96.18 ± 1.0 %, and Jacquard score of 92.77 ± 1.9 %, after 5-fold cross validation. The ablation lesion was detected with an overall Dice score of 94.16 ± 0.2 %. This method can be used in combination with high-resolution electrical mapping to define the optimal ablation dose for gastric ablation.Clinical Relevance-This work presents an automated method to quantify the ablation lesion in the stomach, which can be applied to determine optimal energy doses for gastric ablation, to enable clinical translation of this promising emerging therapy.

High-Resolution Mapping of Intestinal Spike Bursts and Motility.

Gastrointestinal (GI) motility and functional disorders affect up to 25% of the American population. Electrophysiological studies had shown a link between these functional motility disorders and abnormalities in GI bioelectrical activity. However, the dynamics between GI electrical activity (slow waves and spike bursts) and motility are not well understood. This study presents a framework to simultaneously record and quantify GI spike bursts and motility in vivo, in high-resolution. The dynamics between spike burst events and motility observed in 4 pig studies were investigated. A clear connection between spike burst patches and localized contractions was observed. The dataset consisted of 685 spike burst events in 191 patches. Contractions were associated with 81 patches. Spike burst patches associated with contractions had significantly higher amplitude, duration, and size compared to the ones that did not show an association. The amplitude, duration, and size of spike burst patches were positively correlated with the contraction strength. The spike burst patch energy displayed the highest correlation (r = 0.74). The contraction strength had a linear trend with spike burst patch energy. However, it could only account for 52% of the variance in contraction strength.

Computational Reconstruction of 3D Stomach Geometry using Magnetic Field Source Localization.

In this study, we investigated the feasibility of computationally reconstructing the 3D geometry of the stomach by performing source localization of the magnetic field (MF) induced from the stomach surface. Anatomically realistic stomach and torso models of a human participant, reconstructed from the CT images, were used in the computations. First, 128 coils with a radius of 5 mm were positioned on different locations on the stomach model. Next, MF at the sensor positions were computed using Bio-Savart law for the currents of 10 and 100 mA. Then, three noise levels were defined using the biomagnetic data recorded from the same participant and two additional sets of generated white-noise resulting in mean signal to noise ratios (SNR) of 20 and 10 dB. Finally, for each combination of the current and noise level, the magnetic dipole (MDP) approximation was performed to estimate coil positions. The performance of the source localization was assessed by computing the goodness of fit (GOF) values and the distance between the coil and the estimated MDP positions. We obtained GOF values over 98% for all coils and a mean localization error of 0.69±0.08 mm was achieved when 100 mA current was used to induce MF and only biomagnetic data was added. When additional white-noise was added, the GOF values decreased to 95% and the mean localization error increased to around 4 mm. A current of 10 mA was enough to localize the coil positions with a mean error around 8 mm even for the highest noise level we tested but for the few coils furthest from the body surface, the error was around 10 cm. The results indicate that source localization using the MDP approximation can successfully extract spatial information of the stomach.Clinical relevance-Extracting the spatial information of the stomach during the recording of the slow wave activity provides new insights in assessing gastric recordings and relating to disorders.

Design and Application of an Inflatable Cuff to Aid High-Resolution Intestinal Slow Wave Recordings.

Intestinal motility is coordinated by myogenic, neuronal and hormonal factors. Myogenic control of motility via bioelectric slow waves (SW) has been investigated using low-resolution and high-resolution (HR) electrical mapping techniques. Due to the highly conformable and irregular surface of the gut, suboptimal coverage of HR recordings may occur. In this study we designed and developed an inflatable cuff as a platform to apply even pressure across the intestinal surface to achieve consistent and reliable recordings. The inflatable cuff and a HR electrode array were applied in vivo to demonstrate the reliability of SW signal acquisition over a range of inflatable pressures (0 - 5 mm Hg). The frequency, amplitude, percentage of viable signals and signal to noise ratio metrics of the SW signals were computed and compared. Overall, with an increase in inflatable pressure from 0 to 5 mm Hg, the frequency did not change, but the amplitude of the SWs decreased from 0.10 to 0.07 mV. The noise levels were consistent across the range of inflatable pressure levels and the percentage of viable SW recordings improved significantly from 57% to 74% after application of 1 mm Hg of pressure. The inflatable and conformable cuff presented in this study provides a reliable platform for HR mapping of bioelectrical events in the intestines and other conformable organs.Clinical Relevance- This framework improves the quality and reliability of bioelectrical high-resolution recordings obtained from the small intestine. In the future, these recordings will improve our understanding of the pathophysiological mechanisms governing intestinal motility disorders and may provide clinicians with new strategies for diagnosis and treatment.

A Spatially-dense Microfabricated Photolithographic Electrode Array for Gastrointestinal Slow Wave Recordings.

Gastrointestinal slow wave activity is, in part, responsible for governing gut motility. Dysrhythmic slow wave activity has been associated with a number of functional motility disorders, but the mechanisms involved are poorly understood. There exist a number of transgenic small animal models with functional motility disorders. However, current slow wave mapping methods are targeted towards humans and large animals and are not readily translatable. To overcome these shortcomings, a novel electrode array was developed using photolithography. The developed photolithographic electrode array (PEA) was experimentally validated in vivo against a standard flexible printed circuit (FPC) array for comparison. Mean amplitudes of 0.13 ± 0.06 mV and 0.88 ± 0.05 mV were reported by the PEA and the FPC array, respectively. Mean signal to noise ratios (SNR) of 13.4 ± 6.4 dB and 8.3 ± 5.1 dB were achieved for the PEA and the FPC array, respectively. Our findings showed that the PEA acquired slow wave signals with higher amplitude and SNR. In this study, we showed that microfabrication techniques could be successfully implemented with optimized resolution for the investigation of normal and abnormal slow wave activity in smaller animals, which will enable a better understanding of the pathophysiological mechanisms and aid in the diagnosis and treatment of gastrointestinal motility disorders.Clinical Relevance - The ability to characterize the slow wave activity in transgenic animals with functional motility disorders would be a critical advance for the diagnosis and treatment of these disorders. Microfabrication techniques enable miniaturization of high-resolution electrode arrays suitable for mapping electrical activity in normal and transgenic small laboratory animals such as rats and mice.

Design of Pressure Sensor Arrays to Assess Electrode Contact Pressure During In Vivo Recordings in the Gut.

The gastrointestinal (GI) tract is in part controlled by slow wave electrical activity. Recordings of slow waves with high-resolution (HR) electrode arrays are used to characterize normal and abnormal conduction pathways. Improving the quality of these electrical recordings is important for developing a better understanding of abnormal activity. Contact pressure is one factor that can affect the quality of electrical recordings. We compared the performance of two pressure sensing devices for measuring HR electrode array contact pressure. A Velostat-based sensor array was custom designed and built in a 4 × 2 conguration (area: 30 mm2 per sensor) to be integrated into electrical recordings. Commercially available FlexiForce A201 sensors were used to compare to the Velostat-based sensors. Benchtop testing of these sensors was performed; the error of the Velostat-based sensors (14-31%) was better than that of the FlexiForce sensors (20-49%) within a range of 2666-6666 Pa. The Velostat-based sensors were also more repeatable than the FlexiForce sensors over the same pressure range. Simultaneous pressure and slow wave recordings were performed in vivo on a rabbit small intestine. The Velostat-based sensors were able to resolve spatiotemporal changes in contact pressure in the range of 0-10 000 Pa.

Trace Mapping: A New Visualization Technique for Analyzing Gastrointestinal High-Resolution Electrical Mapping Data.

Visualization techniques are an important tool for understanding high-resolution mapping data in gastric electrophysiology. Isochronal maps and animations provide excellent depictions of spatial propagation patterns, but fail to capture temporal features of electrical activity. In this work, 'trace mapping' was developed and validated as a method for visualizing high-resolution mapping data. A combination of dots and lines represent events and temporal groups, respectively, creating patterns that can be quickly and efficiently interpreted. This work outlines trace mapping methods and introduces a shape-based pattern recognition method for efficient interpretation of trace maps. These methods provide a new perspective for understanding and evaluating gastric electrophysiology.Clinical Relevance-This work provides new visualization methods that can help clinicians interpret and diagnose gastric electrical abnormalities in patients with functional gastrointestinal disorders.

Transmural Temperature Monitoring to Quantify Thermal Conduction And Lesion Formation During Gastric Ablation, an Emerging Therapy for Gastric Dysrhythmias.

Gastric ablation is emerging as a potential therapy for electrical dysrhythmias associated with gastric disorders. Thermal conduction properties of gastric tissue during ablation have not yet been defined, but are necessary for optimizing the technique and translating ablation to clinical therapy. We developed custom needle-based transmural temperature probes to quantify the temperature of gastric tissue during ablation. These probes were applied in vivo in pigs (n=5), during gastric ablation (70 °C, 10 s duration), at distances of 2.5 - 20 mm from the ablation catheter tip. Thermal response of the tissue was non-linear; the maximum temperature increase from baseline (33.3 ± 1.0 °C) was observed at the closest temperature probe to the catheter tip (2.5 mm, 14.9 °C), and temperature change decreased with distance from the catheter tip. Probes positioned between 5 -20 mm from the catheter tip recorded temperature increases of less than 5.6 °C. This study provides methods for monitoring temperature during in vivo ablation, and demonstrates that functional temperature increases from ablation were restricted to within approximately 5 mm of the catheter. These methods can now be applied to optimize effective ablation parameters, and to inform models of gastric ablation.

Effects of Electrode Diameter and Contact Material on Signal Morphology of Gastric Bioelectrical Slow Wave Recordings.

Gastric motility is governed in part by bioelectrical 'slow waves', and high-resolution electrical mapping has emerged as a clinical research tool with diagnostic potential. In this study, we aimed to determine the effects of electrode diameter and contact material on in vivo extracellular slow wave recordings to inform gastric mapping device design. Custom flexible-printed-circuit electrode arrays were designed with four electrode diameters (0.3, 1.8, 3.3, 4.8 mm; 4 × 8 array) and fabricated in four contact materials (gold, silver, copper, silver-chloride). The electrode arrays were placed on the gastric serosa in vivo in pigs and unipolar slow wave signals were simultaneously recorded from each electrode. Propagation, signal morphology, and noise were quantified to determine which electrodes produced signals with the highest signal-to-noise ratio (SNR) and gradient, which is a preferred metric for detection and analytical algorithms. Electrodes of diameters 0.3 and 1.8 mm recorded significantly higher signal gradients than 3.3 and 4.8 mm (p < 0.05). Silver-chloride electrodes recorded a significantly higher gradient than all other materials (p < 0.05), with no significant differences between gold, silver, and copper electrodes. Electrodes of diameters 1.8 and 3.3 mm recorded significantly higher SNR than 0.3 mm (p < 0.05). Electrodes with a diameter of 1.8 mm provided an optimal combination to maximize the signal gradient and SNR, and silver-chloride electrodes yielded the highest signal gradient. These results can now inform gastric mapping device design, particularly minimally-invasive devices where electrode size is critical.

Slow-wave coupling across a gastroduodenal anastomosis as a mechanism for postsurgical gastric dysfunction: evidence for a "gastrointestinal aberrant pathway".

Postsurgical gastric dysfunction is common, but the mechanisms are varied and poorly understood. The pylorus normally acts as an electrical barrier isolating gastric and intestinal slow waves. In this report, we present an aberrant electrical conduction pathway arising between the stomach and small intestine, following pyloric excision and surgical anastomosis, as a novel disease mechanism. A patient was referred with postsurgical gastroparesis following antrectomy, gastroduodenostomy, and vagotomy for peptic ulceration. Scintigraphy confirmed markedly abnormal 4-h gastric retention. Symptoms included nausea, vomiting, postprandial distress, and reflux. Intraoperative, high-resolution electrical mapping was performed across the anastomosis immediately before revision gastrectomy, and the resected anastomosis underwent immunohistochemistry for interstitial cells of Cajal. Mapping revealed continuous, stable abnormal retrograde slow-wave propagation through the anastomosis, with slow conduction occurring at the scar (4.0 ± 0.1 cycles/min; 2.5 ± 0.6 mm/s; 0.26 ± 0.15 mV). Stable abnormal retrograde propagation continued into the gastric corpus with tachygastria (3.9 ± 0.2 cycles/min; 1.6 ± 0.5 mm/s; 0.19 ± 0.12 mV). Histology confirmed ingrowth of atypical ICC through the scar, defining an aberrant pathway enabling transanastomotic electrical conduction. In conclusion, a "gastrointestinal aberrant pathway" is presented as a novel proposed cause of postsurgical gastric dysfunction. The importance of aberrant anastomotic conduction in acute and long-term surgical recovery warrants further investigation.NEW & NOTEWORTHY High-resolution gastric electrical mapping was performed during revisional surgery in a patient with severe gastric dysfunction following antrectomy and gastroduodenostomy. The results revealed continuous propagation of slow waves from the duodenum to the stomach, through the old anastomotic scar, and resulting in retrograde-propagating tachygastria. Histology showed atypical interstitial cells of Cajal growth through the anastomotic scar. Based on these results, we propose a "gastrointestinal aberrant pathway" as a mechanism for postsurgical gastric dysfunction.

Dynamic slow-wave interactions in the rabbit small intestine defined using high-resolution mapping.

BACKGROUND: The motility in the small intestine is governed in part by myogenic bio-electrical events, known as slow waves. High-resolution multi-electrode mapping has improved our understanding of slow-wave propagation in the small intestine but has been applied in a limited number of in vivo animal studies. This study applied high-resolution mapping to investigate slow waves in the rabbit small intestine. METHODS: A high-resolution flexible printed circuit board array (256 electrodes; 4 mm spacing) was applied in vivo to the rabbit intestine. Extracellular slow-wave activity was acquired sequentially along the length of the intestine. KEY RESULTS AND CONCLUSIONS: The majority of the slow waves propagated in the antegrade direction (56%) while retrograde patterns were primarily observed in the distal intestine (29%). Colliding slow-wave events were observed across the length of the small intestine (15%). The interaction of competing pacemakers was mapped in spatiotemporal detail. The frequency and velocity of the slow waves were highest in the duodenum compared to ileum (20.0 ± 1.2 cpm vs 10.5 ± 0.9 cpm, P < 0.001; 14.4 ± 3.4 mm/s vs 12.3 ± 3.4 mm/s; P < 0.05). INFERENCES: In summary, extracellular serosal slow-wave activity was quantified spatiotemporally along the length of the rabbit intestine. In particular, the study provides evidence toward the presence and interaction of slow-wave pacemakers acting along the small intestine and how they may contribute to the slow-wave frequency gradient along the length of the intestine.

Multi-day, multi-sensor ambulatory monitoring of gastric electrical activity.

OBJECTIVE: Bioelectrial signals known as slow waves play a key role in coordinating gastric motility. Slow wave dysrhythmias have been associated with a number of functional motility disorders. However, there have been limited human recordings obtained in the consious state or over an extended period of time. This study aimed to evaluate a robust ambulatory recording platform. APPROACH: A commercially available multi-sensor recording system (Shimmer3, ShimmerSensing) was applied to acquire slow wave information from the stomach of six humans and four pigs. First, acute experiments were conducted in pigs to verify the accuracy of the recording module by comparing to a standard widely employed electrophysiological mapping system (ActiveTwo, BioSemi). Then, patients with medically refractory gastroparesis undergoing temporary gastric stimulator implantation were enrolled and gastric slow waves were recorded from mucosally-implanted electrodes for 5 d continuously. Accelerometer data was also collected to exclude data segments containing excessive patient motion artefact. MAIN RESULTS: Slow wave signals and activation times from the Shimmer3 module were closely comparable to a standard electrophysiological mapping system. Slow waves were able to be recorded continuously for 5 d in human subjects. Over the 5 d, slow wave frequency was 2.8 ± 0.6 cpm and amplitude was 0.2 ± 0.3 mV. SIGNIFICANCE: A commercial multi-sensor recording module was validated for recording electrophysiological slow waves for 5 d, including in ambulatory patients. Multiple modules could be used simultaneously in the future to track the spatio-temporal propagation of slow waves. This framework can now allow for patho-electrophysiological studies to be undertaken to allow symptom correlation with dysrhythmic slow wave events.

A Novel Gastric Pacing Device to Modulate Slow Waves and Assessment by High-Resolution Mapping.

OBJECTIVE: The use of electrical pacing in the gastrointestinal field continues to advance clinical and basic science; however, the efficacy and effectiveness of gastric stimulation and pacing remains limited. In the stomach, rhythmic bioelectrical events, known as slow waves, coordinate the muscular contractions that aid digestion. A range of slow wave abnormalities have been shown to be associated with functional motility disorders, such as gastroparesis, chronic unexplained nausea and vomiting, and functional dyspepsia. Pacing is an attractive therapeutic approach to revert slow wave abnormalities. However, there are currently no clinical gastric pacing devices in active use. In this study, a novel battery-powered pacing device was developed, implementing wireless control and tissue electrical parameter monitoring. METHODS: The pacing device was applied in five pigs in vivo along with high-resolution (HR) mapping to validate the device and to elucidate the pacing response of slow waves. The pacing leads were placed in the middle of the HR array to determine any changes to the propagation pattern. The pacing period range was 14-30 s. RESULTS: In all studies, the novel pacing device initiated slow wave activation from a location near the pacing leads at the specified period. Slow wave propagation speed increased after pacing (from 6.4 ± 2.0 to 8.1 ± 3.2 mm/s; P < 0.001), commensurate with induction of paced anisotropic propagation. CONCLUSION: This study introduces a novel gastric pacing system suitable for clinical trials, achieving reliable induction of slow wave pacing at specific location and periods. The device is now available to be trialed as a therapeutic application for motility disorders and obesity.

Feasibility of High-Resolution Electrical Mapping for Characterizing Conduction Blocks Created by Gastric Ablation.

The interstitial cells of Cajal (ICC) initiate, coordinate and propagate bioelectrical slow wave activity that drives gastric motility. In the healthy human stomach, slow wave activity is highly organized. Gastric motility disorders are associated with dysrhythmias. While ablation is widely used to treat cardiac dysrhythmias, this approach has yet to be trialed in the stomach. In this study, radiofrequency (RF) ablation was applied in pig stomachs in vivo to create targeted electrical conduction blocks. Ablations were performed at temperature control mode (55-70°C), and resultant conduction blocks were identified and verified using high-resolution electrical mapping. Termination of slow wave propagation at ablation sites was confirmed by a decrease in extracellular slow wave amplitude from 1.7 ± 0.2 mV to an undetectable amplitude, as well as spatiotemporal pattern analysis of conduction blocks. The use of high-resolution electrical mapping can now be employed to investigate ablation as a potential therapy for gastric dysrhythmias in motility disorders.

Methods for Visualization of Gastric Endoscopic Mapping Data From Three-Dimensional, Non-Uniform Electrode Arrays.

Methods were developed for visualizing three-dimensional endoscopic slow wave mapping data. Simulations representative of normal and abnormal slow wave propagation patterns were generated, allowing qualitative and quantitative evaluation of gridded and spherical interpolation algorithms. Three-dimensional isochronal maps provided a visual representation of slow wave propagation patterns, while mean absolute errors provided a quantitative metric for interpolation performance. Spherical thin plate spline interpolation provided an improvement over current gridded interpolation methods, with a 1.5 to 3.0 fold reduction of mean absolute errors (0.25-0.30 s to 0.08-0.15 s) over three classes of propagation patterns. Different electrode arrangements and densities were tested. A 128-electrode Fibonacci spiral arrangement was proposed as an efficient layout for capturing slow wave dynamics. These methods provide a new visualization technique suitable for endoscopic mapping, and provide a framework for testing and evaluating new interpolation techniques and device designs.

A Framework for Spatiotemporal Analysis of Gastrointestinal Spike Burst Propagation.

Gastrointestinal spike bursts are a bioelectrical phenomenon associated with motility. These events when initiated propagate a small distance and abruptly terminate activating a small area defined as a patch. Understanding normal and abnormal propagation patterns of these events may shed light on the root causes of functional motility disorders. This study develops an automated framework for spatiotemporal analysis of spike bursts. High-resolution electrical signals were obtained from the pig intestine, after which intestinal spike bursts were identified and clustered into their propagating wavefronts. Propagation velocity was estimated by fitting a polynomial surface to the activation times. The fit was able to estimate the velocity of spike burst patches covering at least six channels with an average RMSE of 0.4 s. Propagation within patches was visualized by plotting the fit as activation maps and velocity maps. Average velocities were calculated to compare the propagation characteristics of different types of patches. In the future, this framework will be extended to generate amplitude maps and spike burst duration maps. These tools can be used to analyze spike patch propagation and their relationship to motility.

Detection of Monophasic Slow-wave Activation Phase Using Wavelet Decomposition.

Gastric bio-electric slow-waves are in part responsible for generating motility. Extracellular recordings of the slow-wave activation phase have yielded significant physiological insight about its spatio-temporal characteristics. With the growth of multi-electrode data and long recording periods, there is a need for automated methods to detect the activation phase in a reliable and accurate manner. In this study, the Variable Threshold Wavelet (VTW) algorithm was developed, featuring wavelet decomposition, to compute the derivative to detect the slow-wave activation phase of monophasic signals. The performance of the VTW algorithm was compared against an existing Falling-Edge, Variable Threshold (FEVT) algorithm. Varying levels of synthetic noise representing ventilator and high-frequency noise were added to in vivo slow-wave recordings. Sensitivity, positive-predictive value, area under the curve (Aroc) metric and percentage improvement metric (PIM) of activation phase identification accuracy were calculated. Compared to the existing FEVT algorithm, the VTW algorithm achieved similar performance in identifying the activation phase of slow-waves with various levels of ventilator noise. In the presence of high-frequency noise, the VTW algorithm improved the Aroc of the existing FEVT algorithm by 11.1%. The VTW algorithm can now be applied to analyze normal and abnormal slow-wave recordings.

Methods for High-Resolution Electrical Mapping in the Gastrointestinal Tract.

Over the last two decades, high-resolution (HR) mapping has emerged as a powerful technique to study normal and abnormal bioelectrical events in the gastrointestinal (GI) tract. This technique, adapted from cardiology, involves the use of dense arrays of electrodes to track bioelectrical sequences in fine spatiotemporal detail. HR mapping has now been applied in many significant GI experimental studies informing and clarifying both normal physiology and arrhythmic behaviors in disease states. This review provides a comprehensive and critical analysis of current methodologies for HR electrical mapping in the GI tract, including extracellular measurement principles, electrode design and mapping devices, signal processing and visualization techniques, and translational research strategies. The scope of the review encompasses the broad application of GI HR methods from in vitro tissue studies to in vivo experimental studies, including in humans. Controversies and future directions for GI mapping methodologies are addressed, including emerging opportunities to better inform diagnostics and care in patients with functional gut disorders of diverse etiologies.