Jue Peng

NEW FOCUSED ULTRASOUND TRANSDUCER FOR FAT CELL DISRUPTION

Being an emerging body-shaping technology of fat cell disruption, high-intensity focused ultrasound has been investigated intensively in recent years for its favorable natures such as painlessness, safety and noninvasion. One of the major problems for the technology, however, is the overheating of transducers. In this study, we modified the transducer design in order to solve the overheating problem. We simulated the performance of the modified design by finite element analysis and fabricated the newly designed transducer. By measuring the actual performance data, we proved that the new design can effectively reduce temperature rise while keeping the acoustic intensity field unaffected.

Design and fabrication of an integrated convex ultrasound endoscope for digestive tract imaging

Endoscopic ultrasound (EUS) goes one step further by combining high-frequency ultrasound with endoscopy. We have developed an 8 MHz, 64-element curvilinear array transducer integrated with a 5-million-pixel CMOS camera module for EUS application. A novel voice coil motor (VCM) for lens focus adjustments was used. This device can not only change the focus position of the lens but can also adjust the tilting angle of the lens to extend the depth of field (DOF). With this new technology, we have improved the image quality of the endoscope. For the ultrasonic transducer part, the measured center frequency and -6 dB fractional bandwidth are 7.9 MHz and 83.5%, respectively. A two-way insertion loss of -42 dB was obtained at the average central frequency. A cross-talk of less than -36 dB was achieved for the adjacent columns at the center frequency. The results show a desirable ultrasonic imaging performance.

A micro self-spin electromagnetic actuator for intravascular ultrasound (IVUS) imaging application

Current IVUS probe utilizes an outer proximal motor and a flexible drive shaft transmitting rotational motion through the bending vessel segment. However, the load-bearing shaft through the long bending vessel generally rotates at unstable speed, leading to imaging distortions. One way to overcome the drawback is to develop a self-spin transducer driven by a micro motor inside the probe. In this study, we present an electromagnetic micro-motor with uniform rotation for minimally invasive medical applications. The micro motor consists of two staggered coils as the stator and a permanent magnet placed in a thin-wall tube as the rotor. A permanent magnet synchronous motor (PMSM) with 6 mm length and 1.2 mm outer diameter was fabricated. The transient motions of the motor at driving frequencies of 30 Hz, 50 Hz and 70 Hz were captured by a high-speed camera with 400 FPS respectively. The initial torque of the motor was also measured as 3.2 μNm with a driving current of 0.1 A. The maximum rotation speed we were able to achieve reached 286 RPS (17160 RPM) at 0.5 A.

Design and fabrication of an electromagnetic micro-motor for intravascular ultrasound (IVUS) imaging

Catheter based intravascular ultrasound (IVUS) imaging is widely used for coronary artery diseases. However, image produced by the current IVUS catheter which utilizes an outer proximal motor and a flexible drive shaft transmitting rotational motion through the bending vessel segment, is easy to distort. In this study, we present an electromagnetic micro-motor as a distal actuator for IVUS imaging. The micro-motor consists of a two-pole permanent magnet as the rotor and two-strand flexible coils as the stator. The size of the prototype electromagnetic micro-motor is 6.4 mm length and 1.5 mm outer diameter. The rotational speed of the micro-motor was characterized by using a laser displacement sensor. The micro-motor can generate several decade revolutions per second (RPS) speed needed for IVUS imaging. A static 3D electromagnetic simulation of the micro-motor was performed to estimate the driving torque. The micro-motor can generate a torque of 14.5 μNm with 1.0A effective driving current. This micro-motor is expected to eliminate the image distortion.

Fabrication and performance of a 10 MHz annular array based on PMN-PT single crystal for medical imaging

In this paper, a novel 7 mm diameter, 8-elements, 10MHz electrical focusing 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (PMN-PT) single crystal annular array using equal area elements, has been designed and evaluated. Separation of elements was achieved using 355 nm ultraviolet laser ablation techniques. A novel electrical interconnection strategy for high frequency array elements was implemented. After the transducer was attached to the electric connection board and packaged, the annual array was tested in a pulse/echo arrangement, whereby the center frequency, bandwidth and two-way insertion loss were measured for each annulus. The annular array produced pulses with a centre frequency of 10 MHz and nearly 78 % bandwidth at -6dB. The average insertion loss was -27 dB at centre frequency. The improved lateral resolution and depth of field from the 50μm aluminum wire phantom image were observed, in which the axial and lateral resolutions at 12 mm depth are found to be 650 μm and 188 μm, respectively. Ultrasonic images of cattle eyes also were obtained with the 10-MHz annual array transducer. In the anterior portion of cattle eye it can be seen that the cornea and iris are well distinguishable. For the clinical ophthalmologic application, the B/D scan is not desirable because the transducer is moved in the axial direction, increasing the possibility of damaging the surface of the cornea. This eight element annular transducer is promising for ophthalmology and dermatology ultrasonic imaging and other high frequency ultrasonic diagnostics applications.

Design and fabrication of a high frequency annular array for medical ultrasound systems

Most high frequency (>15MHz) medical ultrasound systems are based on single element transducers mechanically scanned. These systems can provide images with excellent resolution. However, single element transducers are often limited by the fixed focal point and small depth of field. High frequency medical ultrasound annular arrays consisting of concentric rings of elements are focused electronically. These arrays are desirable to avoid the fixed focal point of the single element transducers and improve the depth of field. This paper demonstrate an over 10MHz annular array transducer with novel piezoelectric single crystal. This transducer exhibits good energy conversion performance with a very low insertion loss at the center frequency. The transducer is promising for intravascular ultrasonic imaging and other applications. This work was supported by the National Natural Science Foundation of China (Grant Nos. 10904093 and 61031003), the Science and Technology Grant Scheme funds from Shenzhen Government (N...

Micromachined PMN-PT single crystal diaphragm for piezoelectric sensing applications

In this article, we demonstrate a piezoelectric micromachined diaphragm device based on PMN-PT single crystal thin layer. The electrical properties of the device are characterized. A finite element analysis is carried out for the fabricated model. Harmonic analysis is performed to investigate the vibrational modalities of the diaphragm. The FEA results show very good agreement with the experimental data. As an application example, a diaphragm device is coated with thiol carboxylic PEG (MW 5,000DA) as a resonator for bio mass sensing. The devices are also useful for many other applications including acoustic sensing, ultrasonic transducing, and vibration sensing, etc.