| Cardiovascular diseases(CVD)are the leading cause of death in China,which account for more than 40% of the deaths for Chinese residents.In China,the latest statistics shows that the mortality rate from CVD was 309.33 per 100000 in urban areas and 265.11 per 100000 in rural areas in 2016.The early diagnosis and treatment of CVD is important to reduce mortality.Intravascular ultrasound(IVUS)is commonly used for clinical diagnosis of CVD,which can acquire the cross-sectional images of vascular,and provide detailed information of plaques and vessel to doctor.In clinical interventions,there are two types of widely used IVUS structures.One is electronically scanned IVUS catheter and the other is mechanically rotating IVUS catheter.The latter has been widely used because of its simple fabrication and higher resolution of images than phased array IVUS catheter.The existing commercial mechanical rotary IVUS catheters are driven by proximal motor which transmits rotation by long flexible draft.However,when the catheter pass through a long bending vessel,the shaft is easy to rub with the wall of the catheter which will cause the distortion of imaging.One way to solve this problem is to utilize a distal motor to drive a transducer or a reflecting mirror.However,the existing research on IVUS catheter with a distal motor integrated a reflect mirror at the tip of the cahteter to change the direction of the sound beam.The motor rotate the mirror to achieve the purpose of scanning.But integrating a mirror will increase the difficulty of integration as well as the size of the top of the catheter which will increase the difficulty for the cahteter to through the cruved segment of the vessel.In this work,a catheter with a novel structure and integrate with a distal micromotor was proposed.Ionic liquid is used as the conductor to connect the motor and the transducer,so that the motor can drive the transducer to transmit ultrasonic waves while driving the transducer to rotate.In order to improve the imaging performance of the catheter,the PMN-PT 1-3 composite single crystal is used as the piezoelectric material of the transducer.The electromagnetic motor with outer diameter of 1.2 mm,length of 3.7 mm,maximum speed of 275 RPS and rotation torque of 2.79 μNm is optimize in this work to meet the requirement that the motor can directly drive the transducer to rotate and activate the transducer to work in the vessel.The intravascular ultrasound catheter was integrated in this paper,the micromotor and the transducer was assembled in the top of the catheter which fill with ionic liquid as the conducting wire and the acoustic couplings.The protype of the IVUS catheter was fabricated with an outer diameter of 2 mm.The center frequency and the-6 dB bandwidth of the catheter are 47 MHz and 98%,respectively.Finally,the data acquisition platform which based LABVIEW was build and the 100 μm tungsten wire and porcine artery was used to test the imaging performance of the catheter.The imaging results show that the catheter can display the position and the number of the target,and distinguish the structure of the vessel.The lateral and axial resolution can be calculated by the result of wire imaging were 31 μm and 192 μm.The experimental results show that the self-rotating IVUS catheter that using ionic liquid as conductive wire can be used to detect vascular disease,and it has a potential to solve nonuniform rotational distortion on IVUS catheter which drive by a proximal motor,and decrease the hard tube in the top of the catheter which drive by a distal motor. |
