High-resolution mapping of in vivo gastrointestinal slow wave activity using flexible printed circuit board electrodes: methodology and validation

Abstract

High-resolution, multi-electrode mapping is providing valuable new insights into the origin, propagation, and abnormalities of gastrointestinal (GI) slow wave activity. Construction of high-resolution mapping arrays has previously been a costly and time-consuming endeavor, and existing arrays are not well suited for human research as they cannot be reliably and repeatedly sterilized. The design and fabrication of a new flexible printed circuit board (PCB) multi-electrode array that is suitable for GI mapping is presented, together with its in vivo validation in a porcine model. A modified methodology for characterizing slow waves and forming spatiotemporal activation maps showing slow waves propagation is also demonstrated. The validation study found that flexible PCB electrode arrays are able to reliably record gastric slow wave activity with signal quality near that achieved by traditional epoxy resin-embedded silver electrode arrays. Flexible PCB electrode arrays provide a clinically viable alternative to previously published devices for the high-resolution mapping of GI slow wave activity. PCBs may be mass-produced at low cost, and are easily sterilized and potentially disposable, making them ideally suited to intra-operative human use.

Figure 1

Schematic of PCB (printed circuit board) electrode; (a) shows the full electrode; (b) shows the plug end of the PCB electrode. There are 68 foot-prints (solid dots) for a standard 68 straight-pin PCB plug. (c) Shows an enlarged view of the recording head with 32 electrode pads on each platform.

Figure 2

Position of electrode platforms as used during validation; (a) three PCB arrays were aligned along the anterior gastric serosal surface (covering a total surface area of 55.74 cm²); (b) 48 channel (48E) silver wire (silicone-embedded) platform on gastric corpus. Validation electrograms from gastric serosa are shown for: (c) selected electrograms from the top PCB (highlighted channels in (a)), obtained from position shown in (a); (d) selected electrograms from 48E platform (highlighted channels in (b))—only those channels corresponding to the approximate position of the top PCB are shown.

Figure 3

A single slow wave event recorded showing: (a) amplitude; and (b) activation time (measured from the point of most negative deflection (derivative).

Figure 4

Activation times are mapped in accordance to (a) the PCB electrode configuration. Local velocity is calculated based on (b) the activation times at the immediate four neighboring electrodes. An example calculation is provided alongside the formula.

Figure 5

Activation map showing the spatiotemporal propagation sequence of a gastric slow wave, constructed from 3 PCB electrodes placed in the position shown in Fig. 2a. Diamonds represent electrode positions, and are colored gray when a channel value has been interpolated.