A High-Frequency Ring-Annular Ultrasound Array for Intravascular Ultrasound Imaging

Intravascular ultrasound (IVUS) imaging has become a valuable diagnostic tool for assessing cardiovascular diseases, enabling real-time visualization of blood vessel morphology and pathologies. This study proposes a ring-annular IVUS array using microfabrication processes to achieve a cost-effective and reliable approach to address the challenge of non-uniform rotational distortion in IVUS imaging. Specifically, a 32-element ring-annular array limited to a 9 Fr (3 mm) catheter with a center frequency of 20 MHz is designed and fabricated. The process involves dicing a three-layer transducer to the designed size, integrating it onto a thin flexible printed circuit (FPC), wrapping it around a tube, applying water-soluble tape and epoxy, then conducting plasma cleaning followed by metal layer deposition and encapsulation with Parylene. The developed ring-annular array is tested for impedance and pulse-echo impulse response, demonstrating a mean center frequency of 21.63 MHz and a mean -6 dB bandwidth of 68.9%. The array achieved an axial resolution of 100 μm in tungsten wire phantom imaging.