Electrical and Computer Eng.

Multihop relaying technology is a promising solution for future cellular and ad hoc wireless communications systems in order to achieve broader coverage and to mitigate wireless channels impairment without the need to use high power at the transmitter. Recently, a new concept that is being actively studied in multihop-augmented networks is multiuser cooperative diversity, where several terminals form a kind of coalition to assist each other with the transmission of their messages. In general, cooperative relaying systems have a source node multicasting a message to a number of cooperative relays, which in turn resend a processed version to the intended destination node. The destination node combines the signal received from the relays, possibly also taking into account the source's original signal. Cooperative diversity exploits two fundamentals features of wireless medium: its broadcast nature and its ability to achieve diversity through independent channels. There are three advantages from this.

Sanmiguel CP, Hagiike M, Mintchev MP, Cruz RD, Phillips EH, Cunneen SA, Conklin JL, Soffer EE. Effect of electrical stimulation of the LES on LES pressure in a canine model. Gastric electrical stimulation modulates lower esophageal sphincter pressure (LESP). High-frequency neural stimulation (NES) can induce gut smooth muscle contractions. To determine whether lower esophageal sphincter (LES) electrical stimulation (ES) can affect LESP, bipolar electrodes were implanted in the LES of four dogs. Esophageal manometry during sham or ES was performed randomly on separate days. Four stimuli were used: 1) low-frequency: 350-ms pulses at 6 cycles/min; 2) high-frequency-1: 1-ms pulses at 50 Hz; 3) highfrequency-2: 1-ms pulses at 20 Hz; and 4) NES: 20-ms bipolar pulses at 50 Hz. Recordings were obtained postprandially. Tests consisted of three 20-min periods: baseline, stimulation/sham, and poststimulation.

electrical stimulation synchronized with intestinal slow waves induces intestinal contractions during phase I and enhanced small intestinal postprandial hypomotility induced by glucagon. SIES may have the therapeutic potential for treating small intestinal motility disorders. (Supported by a grant from American Diabetes Association).

Twenty-four-hour ambulatory pH monitoring is an essential tool for diagnosing gastroesophageal reflux disease (GERD). Simultaneous impedance and pH monitoring of the esophagus improves the detection and characterization of GERD. Conventional catheter-based monitoring systems are uncomfortable and interfere with the normal activity of the patient. To overcome these disadvantages, different wireless esophageal monitoring systems have been proposed. A capsule containing sensors for impedance and pH monitoring with wireless communication capabilities is presented. A low cost miniature microcontroller was utilized for interfacing between the sensors and a wireless transmitter. The microcontroller program allowed efficient management of the electric power provided by a 3-V battery. Magnetic holding is proposed as an alternative to surgical affixation of the monitoring capsule. Permanent neodymium magnets separated by 27 cm successfully held the capsule in a test tube. Experimental results demonstrated that friction force can aid magnetic holding to overcome peristalsis. The proposed design efficiently detected acid and nonacid reflux. More research regarding the holding method and capsule packaging are necessary to optimize the mechanical performance of the proposed design in order to facilitate clinical testing on human subjects.

hypoglycemia and gastroparesis to develop a risk factor model. The model was applied to the 2009 dataset for validation. Results: In 2008, there were 53.4 million (95% CI 45.4 million -61.6 million) visits for T2DM. Of these, 658,767 (95% CI 234,319 -1,083,215) were for hypoglycemia and 152,751 (95% CI: 0-350,141) were for gastroparesis. When adjusted for payor status, age, gender, comorbidities and medication use, gastroparesis was associated with a significantly lower risk of hypoglycemia. Validation with 2009 data revealed a concordance of 88% between predicted and observed hypoglycemia events. Conclusions: T2DM patient visits with gastroparesis were associated with a significantly lower risk of hypoglycemia compared to those without gastroparesis. Due to sampling design and the rarity of gastroparesis, there were very few sampled visits with gastroparesis, resulting in large confidence intervals. Thus, the results need to be confirmed in larger samples. Another limitation is that these analyses are based on cross-sectional data and laboratory confirmation of hypogyemia was not available. While gastoparesis is often associated with labile glycemic control, these results are consistent with the mechanism of action of GLP-1 receptor agonists, which blunt postprandial hyperglycemia by slowing gastric emptying without causing hypoglycemia.

Esophageal motility disorders are diagnosed by monitoring pressure, pH, and bolus transit in the lumen of the organ. However, an integrated multichannel esophageal catheter capable of monitoring all these phenomena in a single clinical test is still lacking. The present work proposes innovative techniques and methods to develop a multichannel integrated esophageal catheter. A novel optical pressure sensor for lower esophageal sphincter location and pressure monitoring is proposed. Proper selection of frequencies and electrode arrangement allows impedance-based monitoring of pH and bolus transit. Moreover, due to the small size of the proposed impedance electrode configuration, monitoring channels can be located at 3-mm intervals, improving the longitudinal resolution of the catheter. Therefore, impedance-based pH level monitoring is now feasible. The proposed optical method for pressure monitoring was evaluated by applying pressure around the designed sensor. Obtained images showed good correlation with applied pressures. A model of the esophagus that mimics esophageal motility was utilized to test the proposed catheter. Repeatability of the impedance measurements related to pH was evaluated. The obtained results satisfied the requirements of the DeMeester and Johnson scoring system for esophageal pH measurements. Gastro-esophageal reflux was simulated in the test model and successfully measured with a spatial resolution of 3-mm. Bolus transit was also simulated and successfully identified. All experimental results demonstrated the feasibility of the proposed design. This innovative catheter overcomes many of the disadvantages of the conventional techniques for esophageal testing, but clinical trials are necessary to verify the validity of the laboratory results.

Video capsule endoscopy (VCE) is a noninvasive method for examining the gastrointestinal tract which has been successful in small intestine studies. Recently, VCE has been attempted in the colon. However, the capsule often tumbles in the wider colonic lumen, resulting in missed regions. Self-stabilizing VCE is a novel method to visualize the colon without tumbling. The aim of the present study was to comparatively quantify the effect of stabilization of a commercially available nonmodified capsule endoscope (CE) MiroCam and its modified self-stabilizing version in acute canine experiments. Two customized MiroCam CEs were reduced in volume at the nonimaging back-end to allow the attachment of a self-expanding, biocompatible stabilizing device. Four mongrel dogs underwent laparotomy and exteriorization of a 15-cm segment of the proximal descending colon. A single CE, either self-stabilizing or nonmodified was inserted through an incision into the lumen of the colon followed by pharmacologically induced colonic peristalsis. The inserted capsule was propelled distally through the colon and expelled naturally through the anus. Novel signal processing method was developed to quantify the video stabilization based on camera tracking a predetermined target point (locale). The average locale trajectory, the average radius movement of the locale, and the maximum rate of change of the locale for sequential images were significantly lower for the stabilized capsules compared to the nonstabilized ones . The feasibility of self-stabilized capsule endoscopy has been demonstrated in acute canine experiments.

Transcutaneous intraluminal impedance measurement (TIIM) is a new method to cutaneously measure gastric contractions by assessing the attenuation dynamics of a small oscillating voltage emitted by a battery-powered ingestible capsule retained in the stomach. In the present study, we investigated whether TIIM can reliably assess gastric motility in acute canine models. Methods. Eight mongrel dogs were randomly divided into 2 groups: half received an active TIIM pill and half received an identically sized sham capsule. After 24-hour fasting and transoral administration of the pill (active or sham), two force transducers (FT) were sutured onto the antral serosa at laparotomy. After closure, three standard cutaneous electrodes were placed on the abdomen, registering the transluminally emitted voltage. Thirty-minute baseline recordings were followed by pharmacological induction of gastric contractions using neostigmine IV and another 30-minute recording. Normalized one-minute baseline and postneostigmine gastric motility indices (GMIs) were calculated and Pearson correlation coefficients (PCCs) between cutaneous and FT GMIs were obtained. Statistically significant GMI PCCs were seen in both baseline and post-neostigmine states. There were no significant GMI PCCs in the sham capsule test. Further chronic animal studies of this novel long-term gastric motility measurement technique are needed before testing it on humans.

This paper presents novel minimally-invasive, catheter-based acoustic interrogation device for monitoring motility dynamics of the lower esophageal sphincter (LES). A micro-oscillator actively emitting sound wave at 16 kHz is located at one side of the LES, and a miniature microphone is located at the other side of the sphincter to capture the sound generated from the oscillator. Thus, the dynamics of the opening and closing of the LES can be quantitatively assessed. In this paper, experiments are conducted utilizing an LES motility dynamics simulator. The sound strength is captured by the microphone and is correlated to the level of LES opening and closing controlled by the simulator. Measurements from the simulator model show statistically significant (p < 0.05) Pearson correlation coefficients (0.905 on the average in quiet environment and 0.736 on the average in noisy environment, D.O.F. = 9). Measuring the level of LES opening and closing has the potential to become a valuab...

This work reports on the progress and development advances in the design of self-stabilizing capsules for imaging the lower part of the gastro-intestinal tract, namely the large intestine (the colon). Macro-level design is reviewed, and the new miniaturized design and its components are described.