PROJECT TITLE :

On the Design of Passive Resonant Circuits to Measure Local Pulse Wave Velocity in a Stent

ABSTRACT:

In-stent restenosis is a frequent complication once stent implantation. This article investigates the look of a passive sensor system to be integrated into a stent for the detection of an in-stent restenosis by measuring the native pulse wave velocity (PWV). The proposed system uses two resonant circuits consisting of a capacitive pressure sensor and a coil as transponders. The pressure sensors are located at the proximal and distal end of the stent. An alternating external magnetic field with a continuing frequency is applied such that the resonance frequencies of the transponders cross the excitation frequency when the pulse wave passes. The time delay between the resonances at the transponders can be captured to obtain the PWV. A model for the measurement system and a correlation between transponder style parameters and minimal resolvable time delay are derived. This correlation is predicated on the criterion that the 3 dB bandwidth of the transponder resonances may not overlap within the measurement time interval. This correlation can be used to design and analyze a transponder system for the proposed measurement system. In an experiment, in which the pressure sensors have been emulated by varactor diodes, it might be shown that the model is valid and that the criterion is appropriate. Finally, the relevant design parameters of the transponders are identified and their limitations investigated.