Forward-viewing intravascular ultrasound: Design and fabrication for high sensitivity 3D imaging of hemodynamics.

OBJECTIVE: Percutaneous coronary intervention (PCI) treats myocardial ischemia by stenting stenotic coronary arteries. Wall shear stress (WSS) is an established indicator of plaque rupture risk and restenosis likelihood, yet is not currently used to guide stenting. To address this gap, we developed a forward-viewing intravascular ultrasound array and demonstrated 3D hemodynamic imaging in coronary artery phantoms. METHODS: A 3 mm, 172 element forward-viewing 2D array was designed, simulated, and fabricated. Field II was used to simulate aperture performance, and finite element modeling was conducted to investigate element geometry effects on vibrational modes. The array was characterized electrically and acoustically, then used to acquire 3D color flow images in coronary artery-mimicking phantoms using plane wave compounding, SVD-based wall filtering, transverse oscillation velocity estimation, and Fourier sine series WSS estimation. RESULTS: The fabricated array achieved a center frequency of 31 MHz, a -6 dB bandwidth of 60%, and a single-element SNR of 20 ± 1 dB, with 164 of 172 elements operational. Lateral and axial resolutions of 170 μm and 150 μm, respectively, were measured at a depth of 5 mm. Peak velocities of 1 cm/s and 2.6 cm/s were measured in straight and stenotic phantoms, and WSS was derived from these 3D images. CONCLUSION: 3D finite element modeling provided new insights into element geometry effects on vibrational modes for IVUS 2D arrays, enabling a 31 MHz center frequency, 60% bandwidth, and 95% yield. This work represents the first demonstration of 3D imaging of WSS using a forward-viewing IVUS 2D array, a step toward IVUS-based hemodynamic guidance.