Over a million percutaneous coronary interventions such as balloon angioplasty and stent deployment are performed in the US every year to treat ischemic heart diseases. A thin (0.014") guidewire is used to lead the catheter insertions in nearly all of these procedures.
Our aim i s to add intravascular ultrasound (IVUS) imaging capability to these guidewires so that cardiologists and interventional radiologists can use this valuable technique as a routine in-situ imaging tool before, during and after interventions without prolonging the procedure time and additional risk to the patient. This flexible IVUS probe will also enable imaging in narrowed and tortuous arteries which cannot be accessed by the existing IVUS probes. The proposed device exploits recent advances in guidewire sensor technology such as pressure (FFR) and flow wires in terms of physical implementation. It uses electrical connections provided on the guidewire for AC power supply for increased safety as well as low phase-noise timebase for wireless/broadband data links. It exploits CMUT-on-CMOS technology to its full extent for electronics integration and in a novel physical arrangement so that 4 separate 1- D phased array IVUS chips provide full cross sectional IVUS images with adequate resolution without any rotation. It integrates broadband (200Mb/s), ultra-compact, short-range, safe and low power (150mW) wireless or over-the-wire data links on the same chip to reduce the cable count down to two, retaining the mechanical performance of the guidewire. Specifically, for initial demonstrations, we plan for 40-45 MHz 1-D CMUT-on- CMOS arrays to match the lateral resolution of commercial 20MHz, 3.5F solid state IVUS arrays. We will investigate a wideband (~200Mb/s) wireless concept based on impulse-radio ultra wideband (IR-UWB) and pulse harmonic modulation (PHM) and two over-the-cable hardwired concepts including RF-back telemetry through power line and fully-differential capacitive readout methods. We will determine the leading candidate from these data link alternatives to implement the IC on a 300umx1000um silicon chip, matching the size of the CMUT IVUS array chips. Finally we will experimentally validate the IVUS on guidewire concept using two-chip (CMUT and Data link) configuration on a PCB through imaging experiments. The proposed project may result in a paradigm shift in interventional cardiology with new diagnostic and therapeutic capabilities for vascular and heart diseases. It will also pave the way for combining FFR and IVUS on a guidewire, essentially implementing 3-in-1 tool, which may improve procedure outcomes in a cost effective manner.
This study will demonstrate the building blocks for an intravascular ultrasound (IVUS) imaging system to be integrated on a 0.014 guidewire, which has the potential to transform IVUS into a routine imaging modality in the catheterization lab. It will help cardiologists and interventional radiologists make more accurate decisions on interventions, enable them to monitor balloon angioplasty and stent placement in-situ, all without a need for time consuming catheter exchanges. Overall, this project will improve the outcome of common coronary interventions, enable imaging of arteries too narrow for current IVUS systems and pave the way for guidewire based combination devices.