An endoscopie imaging system based on a two-dimensional CMUT array: real-time imaging results

Real-time catheter-based ultrasound imaging tools are needed for diagnosis and image-guided procedures. The continued development of these tools is partially limited by the difficulty of fabricating two-dimensional array geometries of piezoelectric transducers. Using capacitive micromachined ultrasonic transducer (CMUT) technology, transducer arrays with widely varying geometries, high frequencies, and wide bandwidths can be fabricated. A volumetric ultrasound imaging system based on a two-dimensional, 16×l6-element, CMUT array is presented. Transducer arrays with operating frequencies ranging from 3 MHz to 7.5 MHz were fabricated for this system. The transducer array including DC bias pads measures 4 mm by 4.7 mm. The transducer elements are connected to flip-chip bond pads on the array back side with 400-μm long through-wafer interconnects. The array is flip-chip bonded to a custom-designed integrated circuit (IC) that comprises the front-end electronics. Integrating the front-end electronics with the transducer array reduces the effects of cable capacitance on the transducer's performance and provides a compact means of connecting to the transducer elements. The front-end IC provides a 27-V pulser and 10-MHz bandwidth amplifier for each element of the array. An FPGA-based data acquisition system is used for control and data acquisition. Output pressure of 230 kPa was measured for the integrated device. A receive sensitivity of 125 mV/kPa was measured at the output of the amplifier. Amplifier output noise at 5 Mhz is 112 nV/√Hz. Volumetric images of a wire phantom and vessel phantom are presented. Volumetric data for a wire phantom was acquired in real-time at 30 frames per second.Publisher's Versio

Thiol-reducing agents abate cholestasis-induced lung inflammation, oxidative stress, and histopathological alterations

Cholestasis is not only influences the hepatic function but also damages many other organs. Lung injury is a critical secondary organ damage associated with cholestasis/cirrhosis. Pulmonary histopathological alterations, respiratory distress, and hypoxia are related to cholestasis/cirrhosis-induced lung injury. It has been found that oxidative stress plays a crucial role in this complication. The current study was designed to investigate the effect of N-acetyl cysteine (NAC) and dithiothreitol (DTT) as thiol-reducing and antioxidant agents against cholestasis-induced lung injury. Bile duct ligated (BDL) rats were monitored for the presence of inflammatory cells, TNF-α, and IgG levels in their broncho-alveolar fluid (BALF) at scheduled time intervals (3, 7, 14, and 28 days post-BDL surgery). These markers reached their highest level in the BALF of BDL rats on day 28 after the surgery. Therefore, in another set of experiments, the BDL animals were treated with NAC (100 and 300 mg/kg/day, i.p, for 28 consecutive days) and DTT (10 and 20 mg/kg/day, i.p, for 28 consecutive days). Meanwhile, a significant increase in the levels of TNF-α and IgG was detected in the BALF of BDL rats. The BALF level of neutrophils, monocytes, and lymphocytes was also significantly increased in cholestatic animals. A significant increase in lung tissue biomarkers of oxidative stress was detected in the BDL rats. It was found that NAC and DTT could significantly blunt pulmonary damage induced by cholestasis. The effects of these agents on oxidative stress biomarkers and inflammatory response seem to play a pivotal role in their mechanisms of protective properties

Comparison of the effectiveness of cognitive therapy and lifestyle modification based on LEARN model on body mass index and psychological well-being of obese women: Comparison of the effectiveness of cognitive therapy and lifestyle modification based on LEARN model on body mass index and psychological well-being of obese women

Introduction: This study aimed to compare the effect of cognitive therapy and lifestyle modification based on LEARN model on weight loss and quality of life and well-being associated with obesity in overweight and obese women. Methods: The study was a quasi-experimental study with pre-test and post-test and a control group. The statistical population included all women in Tehran with the age range 21-43 years, and body mass index higher than 25. For this purpose, 45 women volunteers were selected based on inclusion criteria and randomly assigned to three groups. Both interventions were held in twelve 90-minute weekly sessions. Subjects in three groups answered the Obesity-Related Well-Being questionnaire before and end of the third and seventh months and their body mass index was also calculated. The collected data were analyzed using SPSS software and repeated measures analysis of variance test. Results: Both cognitive therapy and lifestyle modification based on LEARN model improved body mass index and obesity-related well-being (P<0.05). There was no significant difference between the two interventions in modifying the research variables (P>0.05).Conclusion: Cognitive therapy and lifestyle modification based on LEARN model improved reduced body weight by correcting destructive beliefs and unhealthy behaviors of overweight and obese women

High-Efficiency Output Pressure Performance Using Capacitive Micromachined Ultrasonic Transducers with Substrate-Embedded Springs

Capacitive micromachined ultrasonic transducers (CMUTs) with substrate-embedded springs offer highly efficient output pressure performance over conventional CMUTs, owing to their nonflexural parallel plate movement. The embedded silicon springs support thick Si piston plates, creating a large nonflexural average volume displacement efficiency in the operating frequency range from 1–3 MHz. Static and dynamic volume displacements of the nonflexural parallel plates were examined using white light interferometry and laser Doppler vibrometry. In addition, an output pressure measurement in immersion was performed using a hydrophone. The device showed a maximum transmission efficiency of 21 kPa/V, and an average volume displacement efficiency of 1.1 nm/V at 1.85 MHz with a low DC bias voltage of 55 V. The device element outperformed the lead zirconate titanate (PZT) ceramic HD3203, in the maximum transmission efficiency or the average volume displacement efficiency by 1.35 times. Furthermore, its average volume displacement efficiency reached almost 80% of the ideal state-of-the-art single-crystal relaxor ferroelectric materials PMN-0.33PT. Additionally, we confirmed that high-efficiency output pressure could be generated from the CMUT device, by quantitatively comparing the hydrophone measurement of a commercial PZT transducer

An integrated circuit with transmit beamforming and parallel receive channels for real-time three-dimensional ultrasound imaging

We present the design of an integrated circuit (IC) that will be flip-chip bonded to a 16 x 16-element CMUT array. The IC provides 16 receive channels which can be configured to receive along either of the array diagonals or on any single row of the array. On transmit, all 256 elements can be used to transmit arbitrarily focused beams. Focused transmission with the full array is made possible by on-chip pulsers and memory. A 25-V pulser and 8-bit shift register is provided for each element of the array. Prior to each transmit, new values are loaded into the shift registers. Current-con trolled one-shots control the transmit pulse widths. Circuit simulations and the IC layout are presented. Simulations predict that delay values can be loaded in less than 1.3 mu s and show the generation of precisely timed pulses. The IC is being prepared for submission to National Semiconductor for fabrication in a high-voltage BiCMOS process.Dr. Karaman is supported by TUBITAK of Turkey through grant 106M33APublisher's Versio

An integrated circuit with transmit beamforming flip-chip bonded to a 2-D CMUT array for 3-D ultrasound imaging

PubMed ID: 19942502State-of-the-art 3-D medical ultrasound imaging requires transmitting and receiving ultrasound using a 2-D array of ultrasound transducers with hundreds or thousands of elements. A tight combination of the transducer array with integrated circuitry eliminates bulky cables connecting the elements of the transducer array to a separate system of electronics. Furthermore, preamplifiers located close to the array can lead to improved receive sensitivity. A combined IC and transducer array can lead to a portable, high-performance, and inexpensive 3-D ultrasound imaging system. This paper presents an IC flip-chip bonded to a 16 x 16-element capacitive micromachined ultrasonic transducer (CMUT) array for 3-D ultrasound imaging. The IC includes a transmit beamformer that generates 25-V unipolar pulses with programmable focusing delays to 224 of the 256 transducer elements. One-shot circuits allow adjustment of the pulse widths for different ultrasound transducer center frequencies. For receiving reflected ultrasound signals, the IC uses the 32-elements along the array diagonals. The IC provides each receiving element with a low-noise 25-MHz-bandwidth transimpedance amplifier. Using a field-programmable gate array (FPGA) clocked at 100 MHz to operate the IC, the IC generated property timed transmit pulses with 5-ns accuracy. With the IC flip-chip bonded to a CMUT array, we show that the IC can produce steered and focused ultrasound beams. We present 2-D and 3-D images of a wire phantom and 2-D orthogonal cross-sectional images (B-scans) of a latex heart phantom.This work was supported by NIH grant CA99059. Work was performed in part at the Stanford Nanofabrication Facility (a member of the National Nanotechnology Infrastructure, Network) which is supported by the National Science Foundation under Grant ECS-9731293.Publisher's Versio

Integrated ultrasonic imaging systems based on CMUT arrays: Recent progress

This paper describes the development of an ultrasonic imaging system based on a two-dimensional capacitive micromachined ultrasonic transducer (CMUT) array. The transducer array and front-end electronics are designed to fit in a 5-mm endoscopic channel. A custom-designed integrated circuit, which comprises the front-end electronics, will be connected with the transducer elements via through-wafer interconnects and flip-chip bonding. FPGA-based signal-processing hardware will provide real-time three-dimensional imaging. The imaging system is being developed to demonstrate a means of integrating the front-end electronics with the transducer array and to provide a clinically useful technology. Integration of the electronics can improve signal-to-noise ratio, reduce the number of cables connecting the imaging probe to a separate processing unit, and provide a means of connecting electronics to large two-dimensional transducer arrays. This paper describes the imaging system architecture and the progress we have made on implementing each of its components: a 16×16 CMUT array, custom-designed integrated circuits, a flip-chip bonding technique, and signal-processing hardware.Publisher's Versio

A miniature real-time volumetric ultrasound imaging system

Progress made in the development of a miniature real-time volumetric ultrasound imaging system is presented. This system is targeted for use in a 5-mm endoscopic channel and will provide real-time, 30-mm deep, volumetric images. It is being developed as a clinically useful device, to demonstrate a means of integrating the front-end electronics with the transducer array, and to demonstrate the advantages of the capacitive micromachined ultrasonic transducer (CMUT) technology for medical imaging. Presented here is the progress made towards the initial implementation of this system, which is based on a two-dimensional, 16×16 CMUT array. Each CMUT element is 250 µm by 250 µm and has a 5-MHz center frequency. The elements are connected to bond pads on the back side of the array with 400-µm long through-wafer interconnects. The transducer array is flip-chip bonded to a custom-designed integrated circuit that comprises the front-end electronics. The result is that each transducer element is connected to a dedicated pulser and low-noise preamplifier. The pulser generates 25-V, 100-ns wide, unipolar pulses. The preamplifier has an approximate transimpedance gain of 500 k? and 3-dB bandwidth of 10 MHz. In the first implementation of the system, one element at a time can be selected for transmit and receive and thus synthetic aperture images can be generated. In future implementations, 16 channels will be active at a given time. These channels will connect to an FPGA-based data acquisition system for real-time image reconstruction.Publisher's Versio