Development of a High-frequency Mini-convex Array Probe for Intraluminal Ultrasonic Imaging Applications

Intraluminal ultrasonic (ILUS) technology, an advanced interventional imaging technique, employs a miniaturized high-frequency ultrasound transducer mounted at the tip of a thin catheter to visualize anatomical structures within the human body. This allows for the acquisition of high-quality images of lesions at close proximity. However, existing ILUS probes predominantly offer specialized visualization in a single direction of the ultrasound catheter due to space constraints within the catheter, posing challenges to the fabrication process. In this study, an ILUS high-frequency mini-convex array probe was developed which featured 64 array elements arranged in curvilinear configuration, providing a 90-degree imaging field of view. The mini-convex array was housed within a stainless-steel tube with an outer diameter of 4 mm, positioned such that its central imaging axis was oriented at a 45-degree angle relative to the axial direction of the tube. This configuration enabled observation of objects ahead of the catheter, even though not entirely covered, and offering detailed features of the interior configuration on its side. This probe exhibited an average center frequency, -6 dB bandwidth, and sensitivity of approximately 17.85 MHz, 61.95%, and 32.64 mV, respectively. Imaging of a wire phantom yielded axial and lateral resolutions at 5 mm depth of approximately 0.11 mm and 0.25 mm, respectively. Subsequently, the actual imaging capability was assessed through ex vivo imaging of the artery and esophagus of a swine, demonstrating the suitability of the high-frequency mini-convex array probe for intraluminal ultrasonic imaging applications.