A Novel Synchronous Micro Motor for Intravascular Ultrasound Imaging

Objective: Intravascular ultrasound (IVUS) is an important method for evaluating lumen dimensions and guiding intervention. However, the current IVUS catheter using a proximal motor and flexible drive shaft is easily rotated at an unstable speed when it passes through along bending vessel. One approach to solve this problem is to develop a catheter driven by a distal motor. Methods: This paper presents a rotation device incorporating a high-frequency transducer as an attempt to facilitate this approach. A novel micro distal synchronous micro motor with 3.7 mm length and 1.2 mm outer diameter was proposed as an actuator for the IVUS catheter. A 0.5 mm × 0.5 mm Pb(Mg
_1/3
Nb
_2/3
)O
₃
-PbTiO
₃
single crystal 1-3 composite single-element transducer was designed and manufactured. The probe is fixed to the front end of the catheter. The 45° reflector, which is opposite to the probe, was used to steer ultrasound to the tissue. Results: The results showed that the maximum torque and rotation speed of the motor were 2.79 μNm and 275 revolutions per second, respectively, at a driving current of 0.34 A. The maximum angular error was 7° at 0.13 A and 30 Hz. The center frequency and -6 dB fractional bandwidth of single element were 34 MHz and 72%, respectively. At the center frequency, the two-way insertion loss was 14 dB. Conclusion: The integrated distal motor IVUS catheter, with small dimensions, a good torque, speed stability, and good ultrasound imaging performance, has tremendous potential in blood vessel imaging. Significance: The novel structure of the catheter could facilitate endoluminal sonography, reducing risks of the clinical diagnosis.