| Catheter-based Intravascular Ultrasound(IVUS)is a minimally invasive catheterization technique that can effectively assess the degree of vascular stenosis and its vessel wall morphology.Commercial IVUS inserts an elongated ultrasound catheter into the coronary artery and obtains a sectional view of the vessel wall through mechanical rotation to achieve real-time detection of vessel wall lesions.However,IVUS catheter using a proximal motor and a flexible drive shaft is easily rotated at unstable speed when it goes through the long bending vessel.One way to solve this problem is to develop a catheter driven by a distal motor.This work presents a rotation device incorporating a high frequency transducer as an attempt to facilitate this approach.A novel micro self-spin synchronous micro motor with 3.7 mm length and 1.2 mm outer diameter was proposed as an actuator of intravascular ultrasound catheter.In order to improve the performance of high frequency transducer,PMN-PT 1-3 composite single crystal with excellent performance is used as a piezoelectric vibrator of high frequency ultrasonic transducer.A 0.5 mm× 0.5 mm single-element transducer and combined instruments imaging platform were completed to verify performance.Some key parameters of motor,transducer and IVUS imaging catheter were evaluated.The instantaneous rotation of the motor is captured by a high-speed camera with a frame rate of 400 fps,and the performance of the motor under the condition of square wave and sine wave driving is analyzed.The maximum speed of the motor is 167 RPS(10020 RPM),the rotation torque is 1.23 ?Nm,the maximum load is 0.1 g,and the maximum rotation error is 22 degrees with square wave driving.The results show that the maximum torque and rotation speed of motor were 2.79 ?Nm and 275 RPS(16500 RPM)at a driving current of 0.34 A by sine wave.The maximum angular error was 7° with 0.13 A at 30 Hz.A center frequency and-6 d B fractional bandwidth of single element were 34 MHz and 72%,respectively.At the center frequency,the two-way insertion loss was 14 dB.The echo amplitude is up to 1530 mV and has excellent sensitivity.Besides,this paper completed the integration of this intravascular ultrasound catheter,made a preliminary research on the performance of different material ultrasonic catheter,and chose an optimal catheter as the catheter material of this article.The assembled micro motor,transducer,tube are integrated together and the imaging performance is tested.The diameter of the assembled tube is 2 mm.The imaging experiment of 100 ?m tungsten wire and porcine artery specimens in vitro were implemented,which demonstrated satisfactory performance of proposed method.The lateral and axial resolution calculated by wire imaging result were 92 ?m and 135 ?m.The integrated self-spin intravascular ultrasound catheter,possessing small dimension,good torque,speed stability,and good ultrasound imaging performance,has great potential in blood vessel imaging.The novel structure of catheter could facilitate endoluminal sonography,reducing risks of clinical diagnose.It was also a solution to solve nonuniform rotational distortion(NURD)on IVUS-based catheter. |
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