Mapping small intestine bioelectrical activity using high-resolution printed-circuit-board electrodes

Abstract

In this study, novel methods were developed for the in-vivo high-resolution recording and analysis of small intestine bioelectrical activity, using flexible printed-circuit-board (PCB) electrode arrays. Up to 256 simultaneous recordings were made at multiple locations along the porcine small intestine. Data analysis was automated through the application and tuning of the Falling-Edge Variable-Threshold algorithm, achieving 92% sensitivity and a 94% positive-predictive value. Slow wave propagation patterns were visualized through the automated generation of animations and isochronal maps. The methods developed and validated in this study are applicable for use in humans, where future studies will serve to improve the clinical understanding of small intestine motility in health and disease.

Fig. 1

Flexible printed-circuit-boards (PCBs) were tessellated into an 8 × 32 electrode configuration, encompassing 256 total electrodes with 4 mm inter-electrode spacing.

Fig. 2

Sample small intestine slow wave recording from the porcine jejunum, showing six cycles of slow waves from one channel of the PCB. The actual slow wave activation time was defined as the point of steepest negative decent [14].

Fig. 3

Sample of nine channels of recorded slow wave activity from the porcine jejunum. Automated slow wave identification from the FEVT algorithm is represented by colored marks. Red circles represent a true positive mark, green triangles represent a false positive mark, and blue squares represent a false negative mark. Amplitude is automatically scaled for each individual channel, but it averaged 36μV in this segment of the intestine.

Fig. 4

Isochronal activation time maps of slow wave propagation. The electrode array was wrapped around the circumference of the intestine such that the top and bottom of each map correspond to nearly-adjacent tissue at the mesenteric border. Each activation map shows a single wavefront, with each color band indicating the area of slow wave propagation per unit time, progressing from red (early) to blue (late), reiterated with arrows. Each black dot represents an electrode, and white dots outlined in red represent electrodes where activity was interpolated. (a) Consistent antegrade propagation. Slow wave activity originates oral to the array and propagates antegrade across the array. Each isochronal color band represents 0.5 s. (b) Consistent retrograde propagation. Slow wave activity originates aboral to the array and propagates retrograde across the array. The isochronal spacing is 1.0 s. (c) Colliding slow wave wavefronts. Slow wave activity originates both oral and aboral to the array and collides in the middle of the array, represented by the dashed white line. The isochronal spacing is 0.25 s.