Biomedical subjects

D J Staton

Publications and source records attributed to D J Staton.

7 recordsLinked to original sources

PubMed1999

The human vector magnetogastrogram and magnetoenterogram.

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.

Analog-Digital Conversion↗

PubMed1997

Superconducting quantum interference device magnetometer for diagnosis of ischemia caused by mesenteric venous thrombosis.

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.

Animals↗

PubMed1996

Magnetoenterography (MENG): noninvasive measurement of bioelectric activity in human small intestine.

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.

Adult↗

PubMed1995

Noninvasive diagnosis of mesenteric ischemia using a SQUID magnetometer.

OBJECTIVE: The authors assessed the ability of a Superconducting Quantum Interference Device (SQUID) magnetometer to noninvasively detect mesenteric ischemia in a rabbit model. SUMMARY BACKGROUND DATA: Superconducting Quantum Interference Device magnetometers have been used to detect magnetic fields created by the basic electrical rhythm (BER) and to detect changes in BER of exteriorized bowel of anesthetized rabbits during mesenteric ischemia. METHODS: The BER of rabbit ileum was noninvasively measured transabdominally using a SQUID magnetometer and compared with the electrical activity recorded with surgically implanted serosal electrodes before, during, and after snare occlusion of the superior mesenteric artery. RESULTS: Transabdominal SQUID recording of BER frequency was highly correlated to the measurements obtained with electrodes (R = 0.91). Basic electrical rhythm frequency decreased from 16.4 +/- 0.8 to 8.3 +/- 0.3 cpm (p < 0.001) after 25 minutes of ischemia. Reperfusion of ischemic bowel resulted in recovery of BER frequency to 14.3 +/- 0.4 cpm 10 minutes after blood flow was restored. CONCLUSIONS: A SQUID magnetometer is capable of noninvasively detecting mesenteric ischemia reliably and at an early stage by detecting a significant drop in BER frequency. These positive findings have encouraged the authors to continue development of clinically useful, noninvasive, detection of intestinal magnetic fields using SQUID magnetometers.

Animals↗

PubMed1994

Diagnosing intestinal ischemia using a noncontact superconducting quantum interference device.

Intestinal ischemia is associated with changes of the basic electric rhythm (BER) of the small intestine. We hypothesized that these changes can be measured noninvasively using a superconducting quantum interference device (SQUID). After general anesthesia, a laparotomy was performed on 10 animals and the jejunum was placed in a nonmagnetic recording chamber containing Krebs' solution at 38 degrees C. Five animals had electrodes placed while five others were placed under the SQUID. Injection of thrombin into the mesenteric artery decreased blood flow (measured with a laser doppler flow-meter) 95% within 5 minutes. SQUID measurements showed significant decreases (P < 0.01 for all changes) in the frequency (15.5 +/- 0.3 to 8.9 +/- 0.2 cycles/min) and the propagation velocity of slow waves (3.5 +/- 0.2 to 1.9 +/- 0.3 sec). The changes in intestinal biomagnetic activity after ischemia were similar to the changes in electrical activity. The SQUID magnetometer is a reliable noncontact device that can detect early intestinal ischemia in animal models. We have recently recorded human small bowel biomagnetic activity using a SQUID magnetometer and believe further technical developments will permit the noninvasive diagnosis of mesenteric ischemia.

Animals↗

PubMed1989

The optical measurement of 1,2-propanediol for the determination of lung capillary permeability surface area.

A technique has been developed which allows for the optical measurement of the concentration-time relationship for a diffusion-limited material in indicator dilution studies. The material, 1-2 propanediol, is used as a probe of the permeability of capillaries in the lung. Comparisons between standard radioisotope measurements and the optical measurements are provided and show excellent agreement. The optical method represents an improvement over the standard radioisotope method in that it provides the same data at lower cost, lower risk, and without the delay required by the radiographic methods.

Animals↗

PubMedDate not supplied

Sulfhemoglobinated erythrocytes as an optical intravascular tracer in the lung.

Sulfhemoglobinated erythrocytes (SHb-RBC's) were examined for utility as an optical multiple indicator dilution tracer in lung studies. A device was developed to measure this tracer optically in flowing blood. Arterial blood was sampled from cannulated, anesthetized dogs and pumped through the device that measured the optical density (OD) of blood at 620 nm. This system was calibrated for increasing SHb-RBC concentrations using an unsteady-state indicator dilution procedure. Areas under optical density (delta OD) profiles were well correlated with injected SHb-RBC volumes using linear regression (r2 > 0.9). This linearity was independent of blood oxygenation, hematocrit, or pH. In vivo lung indicator dilution studies in the intact dog were performed and compared to radioisotope indicator studies using 51Cr labeled erythrocytes. Coefficient of variation (CV) between the two curves was 0.065 under baseline conditions, 0.085 for studies performed during hypoxia, and 0.073 after pH was lowered. We conclude that this device linearly measured SHb-RBC content in whole blood and that SHb-RBC is as accurate a lung indicator dilution tracer as 51Cr-erythrocytes.

Animals↗