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Kuruppu S, Cheng LK, Angeli-Gordon TR, Avci R, Paskaranandavadivel N. Electromechanical Response of Mesenteric Ischemia Defined Through Simultaneous High-Resolution Bioelectrical and Video Mapping. Ann Biomed Eng 2024; 52:588-599. [PMID: 37962674 DOI: 10.1007/s10439-023-03404-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2023] [Accepted: 10/31/2023] [Indexed: 11/15/2023]
Abstract
Intestinal motility is governed in part by bioelectrical slow-waves and spike-bursts. Mesenteric ischemia is a substantial clinical challenge, but its electrophysiological and contractile mechanisms are not well understood. Simultaneous high-resolution bioelectrical and video mapping techniques were used to capture the changes in slow-waves, spike-bursts, and contractile activity during baseline, ischemia, and reperfusion periods. Experiments were performed on anesthetized pigs where intestinal contractions were quantified using surface strain and diameter measurements, while slow-wave and spike-bursts were quantified using frequency and amplitude. Slow-waves entrainment within the ischemic region diminished during ischemia, resulting in irregular slow-wave activity and a reduction in the frequency from 12.4 ± 3.0 cycles-per-minute (cpm) to 2.5 ± 2.7 cpm (p = 0.0006). At the end of the reperfusion period, normal slow-wave entrainment was observed at a frequency of 11.5 ± 2.9 cpm. There was an increase in spike-burst activity between the baseline and ischemia periods (1.1 ± 1.4 cpm to 8.7 ± 3.3 cpm, p = 0.0003) along with a spasm of circumferential contractions. At the end of the reperfusion period, the frequency of spike-bursts decreased to 2.7 ± 1.4 cpm, and contractions subsided. The intestine underwent tonal contraction during ischemia, with the diameter decreasing from 29.3 ± 2.6 mm to 21.2 ± 6.2 mm (p = 0.0020). At the end of the reperfusion period, the intestinal diameter increased to 27.3 ± 3.9 mm. The decrease in slow-wave activity, increase in spike-bursts, and tonal contractions can objectively identify ischemic segments in the intestine. It is anticipated that the use of electrophysiological slow-wave and spike-burst biomarkers, along with contractile measures, could identify mesenteric ischemia in surgical settings and allow an objective biomarker for successful revascularization.
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Affiliation(s)
- Sachira Kuruppu
- Auckland Bioengineering Institute, University of Auckland, Private Bag 92019, Auckland, 1142, New Zealand
| | - Leo K Cheng
- Auckland Bioengineering Institute, University of Auckland, Private Bag 92019, Auckland, 1142, New Zealand
- Riddet Institute, Centre of Research Excellence, Palmerston North, New Zealand
| | - Timothy R Angeli-Gordon
- Auckland Bioengineering Institute, University of Auckland, Private Bag 92019, Auckland, 1142, New Zealand
| | - Recep Avci
- Auckland Bioengineering Institute, University of Auckland, Private Bag 92019, Auckland, 1142, New Zealand
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2
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Somarajan S, Muszynski ND, Olson JD, Bradshaw LA, Richards WO. Magnetoenterography for the Detection of Partial Mesenteric Ischemia. J Surg Res 2019; 239:31-37. [PMID: 30782544 DOI: 10.1016/j.jss.2019.01.034] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2018] [Revised: 12/03/2018] [Accepted: 01/10/2019] [Indexed: 10/27/2022]
Abstract
BACKGROUND Acute mesenteric ischemia represents a life-threatening gastrointestinal condition. A noninvasive diagnostic modality that identifies mesenteric ischemia patients early in the disease process will enable early surgical intervention. Previous studies have identified significant changes in the small-bowel electrical slow-wave parameters during intestinal ischemia caused by total occlusion of the superior mesenteric artery. The purpose of this study was to use noninvasive biomagnetic techniques to assess functional physiological changes in intestinal slow waves in response to partial mesenteric ischemia. METHODS We induced progressive intestinal ischemia in normal porcine subjects (n = 10) by slowly increasing the occlusion of the superior mesenteric artery at the following percentages of baseline flow: 50%, 75%, 90%, and 100% while simultaneous transabdominal magnetoenterogram (MENG) and serosal electromyogram (EMG) recordings were being obtained. RESULTS A statistically significant serosal EMG amplitude decrease was observed at 100% occlusion compared with baseline, whereas no significant change was observed for MENG amplitude at any progressive occlusion levels. MENG recordings showed significant changes in the frequency and percentage of power distributed in bradyenteric and normoenteric frequency ranges at 50%, 75%, 90%, and 100% vessel occlusions. In serosal EMG recordings, a similar percent power distribution (PPD) effect was observed at 75%, 90%, and 100% occlusion levels. Serosal EMG showed a statistically significant increase in tachyenteric PPD at 90% and 100% occlusion. We observed significant increase in tachyenteric PPD only at the 100% occlusion level in MENG recordings. CONCLUSIONS Ischemic changes in the intestinal slow wave can be detected early and noninvasively even with partial vascular occlusion. Our results suggest that noninvasive MENG may be useful for clinical diagnosis of partial mesenteric ischemia.
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Affiliation(s)
- Suseela Somarajan
- Department of General Surgery, Vanderbilt University Medical Center, Nashville, Tennessee; Department of Physics & Astronomy, Vanderbilt University, Tennessee.
| | - Nicole D Muszynski
- Department of General Surgery, Vanderbilt University Medical Center, Nashville, Tennessee; Department of Physics & Astronomy, Vanderbilt University, Tennessee
| | - Joseph D Olson
- Department of General Surgery, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Leonard A Bradshaw
- Department of General Surgery, Vanderbilt University Medical Center, Nashville, Tennessee; Department of Physics & Astronomy, Vanderbilt University, Tennessee; Department of Physics, Lipscomb University, Nashville, Tennessee
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3
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Du P, Paskaranandavadivel N, Angeli TR, Cheng LK, O'Grady G. The virtual intestine: in silico modeling of small intestinal electrophysiology and motility and the applications. WILEY INTERDISCIPLINARY REVIEWS-SYSTEMS BIOLOGY AND MEDICINE 2015; 8:69-85. [PMID: 26562482 DOI: 10.1002/wsbm.1324] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/10/2015] [Revised: 10/01/2015] [Accepted: 10/02/2015] [Indexed: 02/06/2023]
Abstract
The intestine comprises a long hollow muscular tube organized in anatomically and functionally discrete compartments, which digest and absorb nutrients and water from ingested food. The intestine also plays key roles in the elimination of waste and protection from infection. Critical to all of these functions is the intricate, highly coordinated motion of the intestinal tract, known as motility, which is coregulated by hormonal, neural, electrophysiological and other factors. The Virtual Intestine encapsulates a series of mathematical models of intestinal function in health and disease, with a current focus on motility, and particularly electrophysiology. The Virtual Intestine is being cohesively established across multiple physiological scales, from sub/cellular functions to whole organ levels, facilitating quantitative evaluations that present an integrative in silico framework. The models are also now finding broad physiological applications, including in evaluating hypotheses of slow wave pacemaker mechanisms, smooth muscle electrophysiology, structure-function relationships, and electromechanical coupling. Clinical applications are also beginning to follow, including in the pathophysiology of motility disorders, diagnosing intestinal ischemia, and visualizing colonic dysfunction. These advances illustrate the emerging potential of the Virtual Intestine to effectively address multiscale research challenges in interdisciplinary gastrointestinal sciences.
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Affiliation(s)
- Peng Du
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | | | - Timothy R Angeli
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - Leo K Cheng
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - Gregory O'Grady
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
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4
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Somarajan S, Muszynski ND, Cheng LK, Bradshaw LA, Naslund TC, Richards WO. Noninvasive biomagnetic detection of intestinal slow wave dysrhythmias in chronic mesenteric ischemia. Am J Physiol Gastrointest Liver Physiol 2015; 309:G52-8. [PMID: 25930082 PMCID: PMC4491509 DOI: 10.1152/ajpgi.00466.2014] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/30/2014] [Accepted: 04/16/2015] [Indexed: 01/31/2023]
Abstract
Chronic mesenteric ischemia (CMI) is a challenging clinical problem that is difficult to diagnose noninvasively. Diagnosis early in the disease process would enable life-saving early surgical intervention. Previous studies established that superconducting quantum interference device (SQUID) magnetometers detect the slow wave changes in the magnetoenterogram (MENG) noninvasively following induction of mesenteric ischemia in animal models. The purpose of this study was to assess functional physiological changes in the intestinal slow wave MENG of patients with chronic mesenteric ischemia. Pre- and postoperative studies were conducted on CMI patients using MENG and intraoperative recordings using invasive serosal electromyograms (EMG). Our preoperative MENG recordings showed that patients with CMI exhibited a significant decrease in intestinal slow wave frequency from 8.9 ± 0.3 cpm preprandial to 7.4 ± 0.1 cpm postprandial (P < 0.01) that was not observed in postoperative recordings (9.3 ± 0.2 cpm preprandial and 9.4 ± 0.4 cpm postprandial, P = 0.86). Intraoperative recording detected multiple frequencies from the ischemic portion of jejunum before revascularization, whereas normal serosal intestinal slow wave frequencies were observed after revascularization. The preoperative MENG data also showed signals with multiple frequencies suggestive of uncoupling and intestinal ischemia similar to intraoperative serosal EMG. Our results showed that multichannel MENG can identify intestinal slow wave dysrhythmias in CMI patients.
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Affiliation(s)
- S. Somarajan
- 1Department of Surgery, Vanderbilt University, Nashville, Tennessee; ,2Department of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee;
| | - N. D. Muszynski
- 1Department of Surgery, Vanderbilt University, Nashville, Tennessee; ,2Department of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee;
| | - L. K. Cheng
- 1Department of Surgery, Vanderbilt University, Nashville, Tennessee; ,3Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand;
| | - L. A. Bradshaw
- 1Department of Surgery, Vanderbilt University, Nashville, Tennessee; ,2Department of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee; ,4Department of Physics, Lipscomb University, Nashville, Tennessee;
| | - T. C. Naslund
- 5Division of Vascular Surgery, Vanderbilt University, Nashville, Tennessee; and
| | - W. O. Richards
- 6Department of Surgery, University of South Alabama College of Medicine, Mobile, Alabama
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5
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Automated algorithm for GI spike burst detection and demonstration of efficacy in ischemic small intestine. Ann Biomed Eng 2013; 41:2215-28. [PMID: 23612912 DOI: 10.1007/s10439-013-0812-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2013] [Accepted: 04/15/2013] [Indexed: 01/09/2023]
Abstract
We present a novel, fully-automated gastrointestinal spike burst detection algorithm. Following pre-processing with SALPA (Wagenaar and Potter, J. Neurosci. Methods 120:113-120, 2002) and a Savitzky-Golay filter to remove unwanted low and high frequency components, candidate spike waveforms are detected utilizing the non-linear energy operator. Candidate waveforms are classified as spikes or artifact by a support vector machine. The new method achieves highly satisfactory performance with >90% sensitivity and positive prediction value. We also demonstrate an application of the new method to detect changes in spike rate and spatial propagation patterns upon induction of mesenteric ischemia in the small intestine. Spike rates were observed to transiently increase 10-20 fold for a duration of ≈600 s, relative to baseline conditions. In ischemic conditions, spike activity propagation patterns included retrograde-longitudinal wavefronts with occasional spontaneous conduction blocks, as well as self-terminating concentric-circumferential wavefronts. Longitudinal and circumferential velocities were 6.8-8.0 cm/s and 18.7 cm/s, respectively.
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6
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Somarajan S, Cassilly S, Obioha C, Bradshaw LA, Richards WO. Noninvasive biomagnetic detection of isolated ischemic bowel segments. IEEE Trans Biomed Eng 2013; 60:1677-84. [PMID: 23335661 DOI: 10.1109/tbme.2013.2240454] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The slow wave activity was measured in the magnetoenterogram (MENG) of normal porcine subjects (N = 5) with segmental intestinal ischemia. The correlation changes in enteric slow wave activity were determined in MENG and serosal electromyograms (EMG). MENG recordings show significant changes in the frequency and power distribution of enteric slow-wave signals during segmental ischemia, and these changes agree with changes observed in the serosal EMG. There was a high degree of correlation between the frequency of the electrical activity recorded in MENG and in serosal EMG (r = 0.97). The percentage of power distributed in brady- and normoenteric frequency ranges exhibited significant segmental ischemic changes. Our results suggest that noninvasive MENG detects ischemic changes in isolated small bowel segments.
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Affiliation(s)
- Suseela Somarajan
- Department of General Surgery and Physics and Astronomy, Vanderbilt University, Nashville, TN 37232, USA.
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Du P, O'Grady G, Davidson JB, Cheng LK, Pullan AJ. Multiscale modeling of gastrointestinal electrophysiology and experimental validation. Crit Rev Biomed Eng 2011; 38:225-54. [PMID: 21133835 DOI: 10.1615/critrevbiomedeng.v38.i3.10] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Normal gastrointestinal (GI) motility results from the coordinated interplay of multiple cooperating mechanisms, both intrinsic and extrinsic to the GI tract. A fundamental component of this activity is an omnipresent electrical activity termed slow waves, which is generated and propagated by the interstitial cells of Cajal (ICCs). The role of ICC loss and network degradation in GI motility disorders is a significant area of ongoing research. This review examines recent progress in the multiscale modeling framework for effectively integrating a vast range of experimental data in GI electrophysiology, and outlines the prospect of how modeling can provide new insights into GI function in health and disease. The review begins with an overview of the GI tract and its electrophysiology, and then focuses on recent work on modeling GI electrical activity, spanning from cell to body biophysical scales. Mathematical cell models of the ICCs and smooth muscle cell are presented. The continuum framework of monodomain and bidomain models for tissue and organ models are then considered, and the forward techniques used to model the resultant body surface potential and magnetic field are discussed. The review then outlines recent progress in experimental support and validation of modeling, and concludes with a discussion on potential future research directions in this field.
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Affiliation(s)
- Peng Du
- Auckland Bioengineering Institute, The University of Auckland, New Zealand.
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Kim JHK, Bradshaw LA, Pullan AJ, Cheng LK. Characterization of gastric electrical activity using magnetic field measurements: a simulation study. Ann Biomed Eng 2010; 38:177-86. [PMID: 19774463 PMCID: PMC2855966 DOI: 10.1007/s10439-009-9804-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2009] [Accepted: 09/15/2009] [Indexed: 01/08/2023]
Abstract
Gastric disorders are often associated with abnormal propagation of gastric electrical activity (GEA). The identification of clinically relevant parameters of GEA using noninvasive measures would therefore be highly beneficial for clinical diagnosis. While magnetogastrograms (MGG) are known to provide a noninvasive representation of GEA, standard methods for their analysis are limited. It has previously been shown in simplistic conditions that the surface current density (SCD) calculated from multichannel MGG measurements provides an estimate of the gastric source location and propagation velocity. We examine the accuracy of this technique using more realistic source models and an anatomically realistic volume conductor model. The results showed that the SCD method was able to resolve the GEA parameters more reliably when the dipole source was located within 100 mm of the sensor. Therefore, the theoretical accuracy of SCD method would be relatively diminished for patients with a larger body habitus, and particularly in those patients with significant truncal obesity. However, many patients with gastric motility disorders are relatively thin due to food intolerance, meaning that the majority of the population of gastric motility patients could benefit from the methods developed here. Large errors resulted when the source was located deep within the body due to the distorting effects of the secondary sources on the magnetic fields. Larger errors also resulted when the dipole was oriented normal to the sensor plane. This was believed to be due to the relatively small contribution of the dipole source when compared to the field produced by the volume conductor. The use of three orthogonal magnetic field components rather than just one component to calculate the SCD yielded marginally more accurate results when using a realistic dipole source. However, this slight increase in accuracy may not warrant the use of more complex vector channels in future superconducting quantum interference device designs. When multiple slow waves were present in the stomach, the SCD map contained only one maximum point corresponding to the more dominant source located in the distal stomach. Parameters corresponding to the slow wave in the proximal stomach were obtained once the dominant slow terminated at the antrum. Additional validation studies are warranted to address the utility of the SCD method to resolve parameters related to gastric slow waves in a clinical setting.
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Affiliation(s)
- J. H. K. Kim
- Auckland Bioengineering Institute, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand
| | - L. A. Bradshaw
- Department of Surgery, Vanderbilt University Medical Center, Nashville, TN, USA
| | - A. J. Pullan
- Auckland Bioengineering Institute, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand
- Department of Surgery, Vanderbilt University Medical Center, Nashville, TN, USA
| | - L. K. Cheng
- Auckland Bioengineering Institute, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand
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9
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Erickson JC, O'Grady G, Du P, Obioha C, Qiao W, Richards WO, Bradshaw LA, Pullan AJ, Cheng LK. Falling-edge, variable threshold (FEVT) method for the automated detection of gastric slow wave events in high-resolution serosal electrode recordings. Ann Biomed Eng 2009; 38:1511-29. [PMID: 20024624 DOI: 10.1007/s10439-009-9870-3] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2009] [Accepted: 12/07/2009] [Indexed: 10/20/2022]
Abstract
High resolution (HR) multi-electrode mapping is increasingly being used to evaluate gastrointestinal slow wave behaviors. To create the HR activation time (AT) maps from gastric serosal electrode recordings that quantify slow wave propagation, it is first necessary to identify the AT of each individual slow wave event. Identifying these ATs has been a time consuming task, because there has previously been no reliable automated detection method. We have developed an automated AT detection method termed falling-edge, variable threshold (FEVT) detection. It computes a detection signal transform to accentuate the high 'energy' content of the falling edges in the serosal recording, and uses a running median estimator of the noise to set the time-varying detection threshold. The FEVT method was optimized, validated, and compared to other potential algorithms using in vivo HR recordings from a porcine model. FEVT properly detects ATs in a wide range of waveforms, making its performance substantially superior to the other methods, especially for low signal-to-noise ratio (SNR) recordings. The algorithm offered a substantial time savings (>100 times) over manual-marking whilst achieving a highly satisfactory sensitivity (0.92) and positive-prediction value (0.89).
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10
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Erickson JC, Obioha C, Goodale A, Bradshaw LA, Richards WO. Detection of small bowel slow-wave frequencies from noninvasive biomagnetic measurements. IEEE Trans Biomed Eng 2009; 56:2181-9. [PMID: 19497806 DOI: 10.1109/tbme.2009.2024087] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
We report a novel method for identifying the small intestine electrical activity slow-wave frequencies (SWFs) from noninvasive biomagnetic measurements. Superconducting quantum interference device magnetometer measurements are preprocessed to remove baseline drift and high-frequency noise. Subsequently, the underlying source signals are separated using the well-known second-order blind identification (SOBI) algorithm. A simple classification scheme identifies and assigns some of the SOBI components to a section of small bowel. SWFs were clearly identified in 10 out of 12 test subjects to within 0.09-0.25 cycles per minute. The method is sensitive at the 40.3 %-55.9 % level, while false positive rates were 0 %-8.6 %. This technique could potentially be used to help diagnose gastrointestinal ailments and obviate some exploratory surgeries.
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11
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O'Mahony GD, Gallucci MR, Córdova-Fraga T, Berch B, Richards WO, Bradshaw LA. Biomagnetic investigation of injury currents in rabbit intestinal smooth muscle during mesenteric ischemia and reperfusion. Dig Dis Sci 2007; 52:292-301. [PMID: 17160467 DOI: 10.1007/s10620-006-9559-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/20/2006] [Accepted: 08/03/2006] [Indexed: 12/29/2022]
Abstract
A noninvasive, sensitive, and specific method of detecting mesenteric ischemia would be of great use in reducing the morbidity and mortality with which it is associated. Acute lesions in polarized electrically coupled tissues lead to injury currents driven by the transmembrane resting potential gradient. These injury currents are an effective indicator of pathophysiology. The presence of near-DC injury currents in rabbit intestinal smooth muscle has already been demonstrated using a Superconducting quantum interference device (SQUID), and the aim of this study was to evaluate the effect of arterial reperfusion upon these currents. We exteriorized the small bowel of 14 New Zealand white rabbits and placed a remotely operated vascular occluder around the distal most artery supplying a 3-in segment of the jejunum. Experiments were conducted in three groups, i.e., control (n=3), ischemia (n=6), and reperfusion following ischemia (n=5). The subject's position was modulated in and out of the biological field detection range of a SQUID magnetometer using a lift constructed of nonmagnetic material. The changes in magnetic field amplitude were 9.3 and 31.01% for the control and ischemia groups, respectively. The reperfusion group first exhibited a decrease of 17.35% from the pre-ischemic to the ischemic period, followed by an increase of 13.88% of the ischemic value after reestablishing perfusion. In conclusion, injury currents in GI smooth muscle that appear during ischemia are reduced to near-pre-ischemic levels during reperfusion.
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Affiliation(s)
- Gavin D O'Mahony
- Department of Surgery, Vanderbilt University School of Medicine, D 5219 MCN, Nashville, Tennessee 37232, USA
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12
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Cordova-Fraga T, Gallucci M, Bradshaw A, Berch B, Richards WO. A biomagnetic assessment of colonic electrical activity in pigs. Physiol Meas 2006; 28:41-8. [PMID: 17151418 DOI: 10.1088/0967-3334/28/1/004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The electrical control activity of the large intestine was recorded in six pigs using a SQUID magnetometer. The study was performed in pre- and post-colectomy/sham-colectomy conditions. The biomagnetic field associated with colonic ECA changed drastically in subjects that underwent the colectomy procedure, whereas the signal for the control animals was nearly unchanged. Power spectral analysis was used to determine the average changes of dominant frequency and amplitude between baseline versus colectomy and sham-colectomy conditions. The dominant frequency was increased by 68 +/- 24% (versus 2 +/- 3% in control). The amplitude was decreased by 69 +/- 24% (versus 13 +/- 17% in control). This is the first study of transabdominal magnetic fields associated with colonic ECA, suggests some of the side effects generated in colectomy surgery and shows the utility of the biomagnetic technique in studies of the large intestine.
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Affiliation(s)
- T Cordova-Fraga
- Department of Surgery, Vanderbilt University, Nashville, TN 37232, USA
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13
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Bradshaw LA, Irimia A, Sims JA, Gallucci MR, Palmer RL, Richards WO. Biomagnetic characterization of spatiotemporal parameters of the gastric slow wave. Neurogastroenterol Motil 2006; 18:619-31. [PMID: 16918726 DOI: 10.1111/j.1365-2982.2006.00794.x] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Certain gastric disorders affect spatiotemporal parameters of the gastric slow wave. Whereas the electrogastrogram (EGG) evaluates electric potentials to determine primarily temporal parameters, fundamental physical limitations imposed by the volume conduction properties of the abdomen suggest the evaluation of gastric magnetic fields. We used a multichannel superconducting quantum interference device magnetometer to study the magnetogastrogram (MGG) in 20 normal human subjects before and after a test meal. We computed the frequency and amplitude parameters of the gastric slow wave from MGG. We identified normal gastric slow wave activity with a frequency of 2.6 +/- 0.5 cycles per minute (cpm) preprandial and 2.8 +/- 0.3 cpm postprandial. In addition to frequency and amplitude, the use of surface current density mapping applied to the multichannel MGG allowed us to visualize the propagating slow wave and compute its propagation velocity (6.6 +/- 1.0 mm s(-1) preprandial and 7.4 +/- 0.4 mm s(-1) postprandial). Whereas MGG and EGG signals exhibited strong correlation, there was very little correlation between the MGG and manometry. The MGG not only records frequency dynamics of the gastric slow wave, but also characterizes gastric propagation. The MGG primarily reflects the underlying gastric electrical activity, but not its mechanical activity.
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Affiliation(s)
- L A Bradshaw
- Department of Surgery, Vanderbilt University, Nashville, TN 37235, USA.
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14
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Lin ASH, Buist ML, Smith NP, Pullan AJ. Modelling slow wave activity in the small intestine. J Theor Biol 2006; 242:356-62. [PMID: 16626759 DOI: 10.1016/j.jtbi.2006.03.004] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2005] [Revised: 03/08/2006] [Accepted: 03/09/2006] [Indexed: 11/17/2022]
Abstract
We have developed an anatomically based model to simulate slow wave activity in the small intestine. Geometric data for the human small intestine were obtained from the Visible Human project. These data were used to create a one-dimensional finite element mesh of the entire small intestine using an iterative fitting procedure. The electrically active components of the intestinal walls were modelled using a modified Fitzhugh-Nagumo cell model embedded within a longitudinal smooth muscle layer and a layer containing Interstitial Cells of Cajal. Within these layers, the monodomain equation was used to describe slow wave propagation. To solve the monodomain equation, a high-resolution finite difference grid, with an average spatial resolution of 0.95 mm, was embedded within each finite element. The resulting simulations of intestinal activity agree with the experimental observation that slow wave frequency gradually declines from 12 cycles per minute (cpm) in the duodenum to 8 cpm at the terminal ileum. Furthermore, the simulations demonstrated a decrease in conduction velocity with distance along the small intestine (10.7 cm/s in the duodenum, 5.1cm/s in the jejunum and 1.4 cm/s in the ileum), matching experimental recordings from the canine small intestine. We conclude that the framework presented here is capable of qualitatively simulating normal slow wave activity in an anatomical model of the small intestine.
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Affiliation(s)
- Anita Shu-Han Lin
- Bioengineering Institute, The University of Auckland, Level 6, 70 Symonds Street, Private Bag 92019, Auckland, New Zealand
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15
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Xu X, Chen JDZ. Inhibitory effects of sildenafil on small intestinal motility and myoelectrical activity in dogs. Dig Dis Sci 2006; 51:671-6. [PMID: 16614987 DOI: 10.1007/s10620-006-3190-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/02/2005] [Accepted: 07/19/2005] [Indexed: 12/09/2022]
Abstract
Previous studies have shown that sildenafil inhibits the esophageal motility in both humans and animals. The aim of this study was to investigate the effects of sildenafil on intestinal myoelectrical activity and motility. The study was composed of 2 experiments and performed in 7 healthy female dogs with a duodenal cannula 20 cm beyond pylorus (19-26 kg). The first experiment was designed to study the effects of sildenafil on intestinal myoelectrical activity and it included 2 sessions each consisting of 30-minute baseline, 15-minute posttreatment (placebo or 100 mg sildenafil) and 90 minutes after a liquid meal. Intestinal myoelectrical activity was recorded during the entire experiment period. The second experiment was aimed to investigate the effect of sildenafil on intestinal motility and was performed immediately after a solid meal. Intestinal motility was measured by a manometric catheter inserted into the small intestine via the duodenum cannula for 30 minutes at baseline and 60 minutes after sildenafil. Sildenafil significantly reduced the amplitude but had no effect on the frequency and regularity of the intestinal myoelectrical activity. Sildenafil significantly inhibited postprandial intestinal contractions. Although the frequency of the contractions was not altered, the mean area under the curve was significantly reduced during the first 30 minutes (P < .03) and second 30 minutes after sildenafil (P < .03); the power of intestinal contractile activities was also significantly reduced during the first 30 minutes (P < .0004) and second 30 minutes after sildenafil (P < .0003) in comparison with baseline. In conclusion, sildenafil inhibits the amplitude of both intestinal contractile activity and intestinal slow waves.
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Affiliation(s)
- Xiaohong Xu
- Division of Gastroenterology, University of Texas Medical Branch, Galveston, Texas, USA
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Irimia A, Richards WO, Bradshaw LA. Magnetogastrographic detection of gastric electrical response activity in humans. Phys Med Biol 2006; 51:1347-60. [PMID: 16481699 DOI: 10.1088/0031-9155/51/5/022] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The detection and characterization of gastric electrical activity has important clinical applications, including the early diagnosis of gastric diseases in humans. In mammals, this phenomenon has two important features: an electrical control activity (ECA) that manifests itself as an electric slow wave (with a frequency of 3 cycles per minute in humans) and an electrical response activity (ERA) that is characterized by spiking potentials during the plateau phase of the ECA. Whereas the ECA has been recorded in humans both invasively and non-invasively (magnetogastrography-MGG), the ERA has never been detected non-invasively in humans before. In this paper, we report on our progress towards the non-invasive detection of ERA from the human stomach using a procedure that involves the application of principal component analysis to MGG recordings, which were acquired in our case from ten normal human patients using a Superconducting QUantum Interference Device (SQUID) magnetometer. Both pre- and post-prandial recordings were acquired for each patient and 20 min of recordings (10 min of pre-prandial and 10 min of post-prandial data) were analysed for each patient. The mean percentage of ECA slow waves that were found to exhibit spikes of suspected ERA origin was 41% and 61% for pre- and post-prandial recordings, respectively, implying a 47% ERA increase post-prandially (P < 0.0001 at a 95% confidence level). The detection of ERA in humans is highly encouraging and points to the possible use of non-invasive ERA recordings as a valuable tool for the study of human gastric disorders.
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Affiliation(s)
- Andrei Irimia
- Living State Physics Laboratories, Department of Physics and Astronomy, Vanderbilt University, Nashville, TN 37235, USA.
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Bradshaw LA, Roy OP, O'Mahony GP, Myers AG, McDowell JG, Wikswo JP, Richards WO. Biomagnetic detection of injury currents in rabbit ischemic intestine. Dig Dis Sci 2005; 50:1561-8. [PMID: 16133952 DOI: 10.1007/s10620-005-2898-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/23/2004] [Accepted: 12/13/2004] [Indexed: 12/09/2022]
Abstract
The presence of direct current (DC) injury currents in ischemic tissue is an important diagnostic indicator of pathophysiology in cortical spreading depression and particularly in myocardial infarction. To date, no measurements of DC injury currents in the alimentary tract have been reported. We used a SQUID magnetometer to measure changes in the baseline of the magnetic field of intestinal electrical activity during induced segmental ischemia. We computed the magnetic field DC baseline by subtracting sequential recordings made while the bowel segment was first directly beneath the SQUID and then pulled away. We observed a significant baseline decrease of 38% +/- 4% in experimental animals, while the control group decreased by only 1% +/- 6%. This magnetic field baseline decrease is consistent with the flow of injury currents between normally perfused and hypoxic tissue regions. This study is the first report of DC injury currents in ischemic smooth muscle of the alimentary tract.
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Affiliation(s)
- L Alan Bradshaw
- Department of Surgery, Vanderbilt University Medical Center, Nashville, Tennessee 37235, USA.
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Irimia A. Electric field and potential calculation for a bioelectric current dipole in an ellipsoid. ACTA ACUST UNITED AC 2005. [DOI: 10.1088/0305-4470/38/37/012] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Bradshaw LA, Myers AG, Redmond A, Wikswo JP, Richards WO. Biomagnetic detection of gastric electrical activity in normal and vagotomized rabbits. Neurogastroenterol Motil 2003; 15:475-82. [PMID: 14507349 DOI: 10.1046/j.1365-2982.2003.00432.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
We recorded the vector magnetogastrogram (MGG) due to gastric electrical activity (GEA) in normal rabbits using a Superconducting QUantum Interference Device (SQUID) magnetometer and measured the degree of correlation of the MGG with 24 channels of serosal electrodes. The vector magnetometer allows us to non-invasively record three orthogonal magnetic field components and project the recorded magnetic field vector into arbitrary directions. We optimized the magnetic field vector direction to obtain the highest possible correlation with each serosal electrode recording. We performed a vagotomy and examined spatial and temporal changes in the serosal potential and in the transabdominal magnetic field. We obtained spatial information by mapping the recorded signals to the electrode positions in the gastric musculature. Temporal evidence of uncoupling was observed in spectral analyses of both serosal electrode and SQUID magnetometer recordings. We conclude that non-invasive recordings of the vector magnetogastrogram reflect underlying serosal potentials as well as pathophysiological changes following vagotomy.
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Affiliation(s)
- L A Bradshaw
- Living State Physics Group, Department of Physics and Astronomy, Vanderbilt University, Nashville, TN 37235, USA.
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Bradshaw LA, Myers A, Wikswo JP, Richards WO. A spatio-temporal dipole simulation of gastrointestinal magnetic fields. IEEE Trans Biomed Eng 2003; 50:836-47. [PMID: 12848351 DOI: 10.1109/tbme.2003.813549] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
We have developed a simulation of magnetic fields from gastrointestinal (GI) smooth muscle. Current sources are modeled as depolarization dipoles at the leading edge of the isopotential ring of electrical control activity (ECA) that is driven by coupled cells in the GI musculature. The dipole moment resulting from the known transmembrane potential distribution varies in frequency and phase depending on location in the GI tract. Magnetic fields in a homogeneous volume conductor are computed using the law of Biot-Savart and characterized by their spatial and temporal variation. The model predicts that the natural ECA frequency gradient may be detected by magnetic field detectors outside the abdomen. It also shows that propagation of the ECA in the gastric musculature results in propagating magnetic field patterns. Uncoupling of gastric smooth muscle cells disrupts the normal magnetic field propagation pattern. Intestinal ischemia, which has been experimentally characterized by lower-than-normal ECA frequencies, also produces external magnetic fields with lower ECA frequencies.
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Affiliation(s)
- L Alan Bradshaw
- Department of Surgery, Vanderbilt University, Nashville, TN 37235, USA.
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Constant-Neto M, Hartmann MJ, Goulart AH, Machado DC, Constant SAR, Cuervo C. Behavior of plasma hemoglobin in an experimental model of occlusive mesenteric ischemia. J Gastrointest Surg 2003; 7:603-5. [PMID: 12850672 DOI: 10.1016/s1091-255x(03)00070-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The difficulties in establishing the diagnosis of mesenteric ischemia are responsible for the high mortality rate that is associated with this clinical condition. We studied the behavior of plasma hemoglobin in an experimental model of occlusive mesenteric ischemia in mice. Our results showed a clear relationship between the duration of ischemia and plasma hemoglobin levels. With regard to the time frames studied (3 hours, 6 hours, 12 hours, and 24 hours), comparison with control groups produced calculated P values of less than 0.01 for all time frames with the exception of the 3-hour group. This test may have the potential to aid in the diagnosis of mesenteric ischemia as well as the follow-up of its course after various therapeutic approaches.
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Affiliation(s)
- Manoel Constant-Neto
- Instituto de Pesquisas Biomédicas da PUCRS, Hospital São Lucas da Pontifícia, Universidade Católica do RS, Porto Alegre, Brasil.
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22
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Chapter 25 Electric fields and currents of the small intestine and their effects on Escherichia coli. ACTA ACUST UNITED AC 2002. [DOI: 10.1016/s1877-1823(09)70141-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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Bradshaw LA, Richards WO, Wikswo JP. Volume conductor effects on the spatial resolution of magnetic fields and electric potentials from gastrointestinal electrical activity. Med Biol Eng Comput 2001; 39:35-43. [PMID: 11214271 DOI: 10.1007/bf02345264] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
An analysis of the relative capabilities of methods for magnetic and electric detection of gastrointestinal electrical activity is presented. The model employed is the first volume conductor model for magnetic fields from GEA to appear in the literature. A mathematical model is introduced for the electric potential and magnetic field from intestinal electrical activity in terms of the spatial filters that relate the bioelectric sources with the external magnetic fields and potentials. The forward spatial filters are low-pass functions of spatial frequency, so more superficial external fields and potentials contain less spatial information than fields and potentials near the source. Inverse spatial filters, which are reciprocals of the forward filters, are high-pass functions and must be regularised by windowing. Because of the conductivity discontinuities introduced by low-conductivity fat layers in the abdomen, the electric potentials recorded outside these layers required more regularisation than the magnetic fields, and thus, the spatial resolution of the magnetic fields from intestinal electrical activity is higher than the spatial resolution of the external potentials. In this study, two smooth muscle sources separated by 5cm were adequately resolved magnetically, but not resolved electrically. Thus, sources are more accurately localized and imaged using magnetic measurements than using measurements of electric potential.
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Affiliation(s)
- L A Bradshaw
- Department of Physics & Astronomy, Vanderbilt University, Nashville, Tennessee, USA.
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Seidel SA, Hegde SS, Bradshaw LA, Ladipo JK, Richards WO. Intestinal tachyarrhythmias during small bowel ischemia. THE AMERICAN JOURNAL OF PHYSIOLOGY 1999; 277:G993-9. [PMID: 10564105 DOI: 10.1152/ajpgi.1999.277.5.g993] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The electrical control activity (ECA) of the bowel is the omnipresent slow electrical wave of the intestinal tract. Characterization of small bowel electrical activity during ischemia may be used as a measure of intestinal viability. With the use of an animal model of mesenteric ischemia, serosal electrodes and a digital recording apparatus utilizing autoregressive spectral analysis were used to monitor the ECA of 20 New Zealand White rabbits during various lengths of ischemia. ECA frequency fell from 18.2 +/- 0.5 cycles per minute (cpm) at baseline to 12.2 +/- 0.9 cpm (P < 0.05) after 30 min of ischemia and was undetectable by 90 min of ischemia in all animals. Tachyarrhythmias of the ECA were recorded in 55% of the animals as early as 25 min after ischemia was induced and lasted from 1 to 48 min. Frequencies ranged from 25 to 50 cpm. These tachyarrhythmias were seen only during ischemia, suggesting that they are pathognomonic for intestinal ischemia. The use of the detection of ECA changes during intestinal ischemia may allow earlier diagnosis of mesenteric ischemia.
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Affiliation(s)
- S A Seidel
- Department of Surgery, Vanderbilt University School of Medicine, Veterans Affairs Medical Center, Vanderbilt University, Nashville, Tennessee 37232, USA
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Prakash NM, Brown MC, Spelman FA, Nelson JA, Read P, Heitkemper MM, Tobin RW, Pope CE. Magnetic field goniometry: a new method to measure the frequency of stomach contractions. Dig Dis Sci 1999; 44:1735-40. [PMID: 10505705 DOI: 10.1023/a:1018896315048] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
A system of magnetic field goniometry was developed for measuring the frequency of stomach contractions. This technique uses a handheld, electronic compass to measure the angular change in direction of a magnetic field generated by a small, ingested magnet. Measurements of gastric mechanical activity made by goniometry were validated with simultaneous measurements using manometry and electrogastrography. The agreement between these different modalities was excellent. In this pilot study, magnetic field goniometry provided an easy, minimally invasive, and accurate method to measure the frequency of gastric contractions.
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Affiliation(s)
- N M Prakash
- Department of Bioengineering, University of Washington, Seattle, USA
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Bradshaw LA, Ladipo JK, Staton DJ, Wikswo JP, Richards WO. The human vector magnetogastrogram and magnetoenterogram. IEEE Trans Biomed Eng 1999; 46:959-70. [PMID: 10431461 DOI: 10.1109/10.775406] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Electrical activity in the gastrointestinal system produces magnetic fields that may be measured with superconducting quantum interference device magnetometers. Although typical magnetometers have detection coils that measure a single component of the magnetic field, gastric and intestinal magnetic fields are vector quantities. We recorded gastric and intestinal magnetic fields from nine abdominal sections in nine normal human volunteers using a vector magnetometer that measures all three Cartesian components of the magnetic field vector. A vector projection technique was utilized to separate the magnetic field vectors corresponding to gastric and intestinal activity. The gastric magnetic field vector was oriented in a cephalad direction, consistent with previously observed data, and displayed oscillatory characteristics of gastric electrical activity (f = 3.03 +/- 0.18 cycles/min). Although the small bowel magnetic field vector showed no consistent orientation, the characteristic frequency gradient of the small bowel electrical activity was observed. Gastric and intestinal magnetic field vectors were oriented in different directions and were thus distinguished by the vector projection technique. The observed difference in direction of gastric and intestinal magnetic field vectors indicates that vector recordings dramatically increase the ability to separate physiological signal components from nonphysiological components and to distinguish between different physiological components.
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Affiliation(s)
- L A Bradshaw
- Department of Physics and Astronomy, Vanderbilt University, Nashville, TN 37235, USA.
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Abstract
PURPOSE Acute mesenteric arterial occlusion is an abdominal catastrophe that carries high morbidity and mortality rates. Current diagnostic methods, however, lack sensitivity and specificity and do not provide information about the viability of the affected bowel. Early diagnosis and intervention would improve patient outcomes and survival rates. The basic electrical rhythm (BER) is the omnipresent electrical slow wave of the gastrointestinal tract that characterizes the underlying electrical activity of the bowel. BER frequency is known to fall with ischemia. Superconducting quantum interference devices (SQUIDs) can detect BER by measuring the magnetic fields generated by the electrical activity of the smooth muscle of the small bowel. The purpose of this study was to determine the ability of a SQUID to detect mesenteric ischemia in a free-lying section of small bowel in an animal model of acute superior mesenteric artery occlusion. METHODS Seven adult male rabbits (six experimental and one control) were studied with transabdominal SQUID and electrode recordings during baseline and after the induction of mesenteric ischemia with balloon occlusion of the superior mesenteric artery. Continuous recordings were taken for 120 minutes of ischemia and analyzed with autoregressive spectral analysis to determine the BER frequency during specific time points of the study. Two independent investigators blinded to the experimental preparation examined the results to determine whether there was decreased BER frequency and thus ischemia. The results are expressed as mean +/- SEM, and paired t tests were used to determine statistical significance. RESULTS BER was detected in all seven animals and fell from 10.7 +/- 0.5 cpm to 7.0 +/- 1.8 cpm after 30 minutes of ischemia in the magnetic channels (P <.05, with t test). The fall in BER was detected by the SQUID in all six experimental animals. The blinded observers correctly identified healthy and ischemic magnetic data recording, with a sensitivity of 94% and specificity of 100%. CONCLUSION SQUIDs can noninvasively detect bowel ischemia early in a free-lying segment of small bowel in this animal model with a high degree of sensitivity and specificity.
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Affiliation(s)
- S A Seidel
- Department of Surgery, Veterans Administration Medical Center, Nashville, TN 37232, USA
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Allescher HD, Abraham-Fuchs K, Dunkel RE, Classen M. Biomagnetic 3-dimensional spatial and temporal characterization of electrical activity of human stomach. Dig Dis Sci 1998; 43:683-93. [PMID: 9558020 DOI: 10.1023/a:1018852208687] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Biomagnetic measurements are based on the noninvasive recording of magnetic signals produced by biological sources such as nervous system and muscle. The aim of this study was to obtain multichannel magnetic field recordings from the human gastrointestinal tract and to localize the sources of these signals three-dimensionally. The magnetic field was recorded in eight human healthy subjects using a sensor array with 37 superconducting quantum interference devices (SQUIDs); an electrogastrogram was recorded simultaneously. Biomagnetic source localization was carried out with an iterative nonlinear optimization algorithm using the model of an equivalent current dipole (ECD) and correlated to magnetic resonance imaging (MRI) in four volunteers. Magnetogastrograms and electrogastrograms demonstrated a similar frequency distribution with a peak at 3/min. In all subjects the centers of the calculated dipoles plotted vs time showed a characteristic migration across the stomach area. One volunteer demonstrated tachygastric episodes, during which his magnetic field amplitudes increased fivefold and his dipole migration disappeared. In absence of an attack his recordings changed to normal. This demonstrates multichannel magnetic recordings can be used to localize the sources of the biomagnetic field, which could be useful for the understanding of motility disturbances.
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Affiliation(s)
- H D Allescher
- II. Medizinische Klinik und Poliklinik der TU München, Germany
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Hegde SS, Seidel SA, Ladipo JK, Bradshaw LA, Halter S, Richards WO. Effects of mesenteric ischemia and reperfusion on small bowel electrical activity. J Surg Res 1998; 74:86-95. [PMID: 9536980 DOI: 10.1006/jsre.1997.5232] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
UNLABELLED Previous studies involving basic electrical rhythm (BER) have not been carried out far enough to fully characterize the relationship between mesenteric ischemia and BER. The phenomenon of reperfusion injury has also not been correlated with BER activity. The goal of this study was to characterize changes in BER during mesenteric ischemia and reperfusion and to correlate them with changes in pathology. METHODS Serosal electrodes were used to record the electrical activity of rabbit jejunum (n = 20) at baseline, during ischemia (90-210 min), and during reperfusion (120-240 min). BER frequency and amplitude were monitored, and biopsies were taken at the end of ischemia and reperfusion. A pathologist blinded to the specimen identity graded the histology on a scale of 0 (no changes) to 6 (transmural necrosis). Paired t test, the Kruskal-Wallis test of non-parametric ranks, and Fisher's r to z test were used for statistical significance where appropriate. RESULTS BER frequency and amplitude fell significantly after 15 min of ischemia and became undetectable by 90 min of ischemia in all animals. The likelihood that BER would return during reperfusion was highly correlated with length of ischemia (r = 0.99). Longer periods of reperfusion were associated with increasing pathologic grade. CONCLUSIONS BER frequency and amplitude are very sensitive to ischemia and their changes occur well before histopathologic changes. The variation in electrical activity of the small bowel during ischemia and reperfusion is a dynamic process that reflects the metabolic state of the smooth muscle. If electrical activity of the bowel is to be used for assessment of viability, continuous recordings more accurately reflect the metabolic state of the smooth muscle.
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Affiliation(s)
- S S Hegde
- Department of Surgery, Vanderbilt University School of Medicine, Nashville, Tennessee, USA
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Allos SH, Staton DJ, Bradshaw LA, Halter S, Wikswo JP, Richards WO. Superconducting quantum interference device magnetometer for diagnosis of ischemia caused by mesenteric venous thrombosis. World J Surg 1997; 21:173-7; discussion 177-8. [PMID: 8995074 DOI: 10.1007/s002689900211] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Although mesenteric venous thrombosis carries a better prognosis than arterial thrombosis, mortality and morbidity are still high. Previous studies have shown that the basic electrical rhythm (BER) of the bowel decreases early after induction of arterial ischemia. Furthermore, our studies have shown that these changes occur prior to pathologic changes and that they can be recorded noninvasively using a superconducting quantum interference device (SQUID). SQUIDs measure magnetic fields that are created by the electrical activity of the gastrointestinal smooth muscle and have been used to measure the BER of the small intestine in human volunteers. This study was conducted to determine if a SQUID could be used for early noninvasive detection of mesenteric venous ischemia in an animal model. Simultaneous recordings from serosal electrodes and a SQUID outside the abdomen were taken from anesthetized New Zealand rabbits. Recordings were made for 15 minutes before and 90 minutes after injection of thrombin into the superior mesenteric vein. The basic electrical rhythm of the small bowel dropped from 16.42 +/- 0.69 to 8.80 +/- 0.74 cycles per minute at 30 minutes and to 6.82 +/- 0.722 after 90 minutes (p < 0.0001, paired t-test). The correlation coefficient between the SQUID and electrical recordings was 0.954 (p < 0.0001). These data suggest that the ischemia caused by mesenteric venous thrombosis results in changes in the bioelectrical activity, which can be noninvasively detected using a SQUID.
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Affiliation(s)
- S H Allos
- Department of Surgery, Veterans Administration Medical Center, 1310 24th Avenue S, Nashville, Tennessee 37203, USA
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Richards WO, Bradshaw LA, Staton DJ, Garrard CL, Liu F, Buchanan S, Wikswo JP. Magnetoenterography (MENG): noninvasive measurement of bioelectric activity in human small intestine. Dig Dis Sci 1996; 41:2293-301. [PMID: 9011432 DOI: 10.1007/bf02100117] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The basic electrical rhythm (BER) of the gastrointestinal tract creates minute magnetic fields that have been measured in animals using a Superconducting QUantum Interference Device (SQUID) gradiometer. The aim of this study was to measure noninvasively the biomagnetic fields of human stomach and small intestine. Twenty-one human volunteers were studied using a 37-channel SQUID gradiometer positioned over the epigastrium and umbilicus. In one volunteer additional biomagnetic recordings were performed in order to map the spatial variation of the biomagnetic fields. Cyclical waveforms consistent with gastric BER [3.0+/-0.5 cycles per minute (cpm)] and small intestine BER (10.26+/-1.74 cpm) were seen in the epigastrium and umbilicus, respectively. The mapping study identified the expected frequency gradient (12.0 cpm in duodenum, 11.3 cpm in jejunum, to 9.7 cpm in ileum) within the small intestine. Noninvasive recordings of human gastric and small intestinal BER can be obtained using a SQUID gradiometer.
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Affiliation(s)
- W O Richards
- Department of Surgery at the Veterans Administration Medical Center, Nashville, Tennessee 37232-5732, USA
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