Miniaturized piezoelectric tube actuated catheter (μPTAC) enabling distal actuation for intravascular optical coherence tomography.

Intravascular optical coherence tomography (IV-OCT) requires stable circumferential scanning, while long torque-transmission shafts can introduce non-uniform rotational distortion (NURD). This study presents a miniature piezoelectric tube-actuated catheter (μPTAC) that integrates a piezoelectric-tube stator, a gradient-index (GRIN) lens rotor, and a single-mode fiber for compact distal scanning. Two orthogonal bending modes excited with a 90° phase difference generate elliptical contact motion and friction-driven lens rotation. Finite element analysis and experimental characterization supported this actuation mechanism. The prototype incorporated a 4-mm-long tube with outer and inner diameters of 0.45 and 0.20 mm, respectively, exhibited a bending resonance at 68.68 kHz, and achieved a rotational speed of 2607 rpm under 50 Vpp excitation. A stationary mirror measurement yielded an axial full width at half maximum of 13.85 μm, while retrospective edge analysis gave an effective lateral width of approximately 34 μm. Analysis of selected vessel-wall images from the earlier and present probes yielded contrast-to-noise ratios (CNRs) of 0.53 ± 0.21 and 0.88 ± 0.17, respectively, and image-domain signal-to-noise ratio (SNR) proxies of 14.3 ± 4.2 and 19.4 ± 3.9 dB under their respective acquisition and processing conditions. Imaging experiments in air demonstrated three-dimensional phantom reconstruction, consistent feature placement, vascular-model navigation, and ex vivo imaging of a stented porcine coronary artery. These results support the integrated μPTAC architecture for compact distal IV-OCT scanning. Future work will focus on developing a distal piezoelectric ultrasonic motor actuator with improved rotational stability and reliability to enable clinical IV-OCT applications.