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Yayın Integrated ultrasonic imaging systems based on CMUT arrays: Recent progress(IEEE, 2004) Wygant, Ira O.; Zhuang, Xuefeng; Yeh, David T.; Nikoozadeh, Amin; Oralkan, Ömer; Ergün, Arif Sanlı; Karaman, Mustafa; Khuri-Yakub, Butrus ThomasThis 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.Yayın An endoscopie imaging system based on a two-dimensional CMUT array: real-time imaging results(IEEE, 2005) Wygant, Ira O.; Zhuang, Xuefeng; Yeh, David T.; Vaithilingam, Srikant; Nikoozadeh, Amin; Oralkan, Ömer; Ergün, Arif Sanlı; Karaman, Mustafa; Khuri-Yakub, Butrus ThomasReal-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-?m 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.Yayın A miniature real-time volumetric ultrasound imaging system(SPIE-Int Soc Optical Engineering, 2005) Wygant, Ira O.; Yeh, David T.; Zhuang, Xuefeng; Nikoozadeh, Amin; Oralkan, Ömer; Ergün, Arif Sanlı; Karaman, Mustafa; Khuri-Yakub, Butrus ThomasProgress 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.Yayın An integrated circuit with transmit beamforming and parallel receive channels for real-time three-dimensional ultrasound imaging(IEEE, 2006) Wygant, Ira O.; Lee, Hyunjoo J.; Nikoozadeh, Amin; Yeh, David T.; Oralkan, Ömer; Karaman, Mustafa; Khuri-Yakub, Butrus ThomasWe 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.Yayın An integrated circuit with transmit beamforming and parallel receive channels for 3D ultrasound imaging: testing and characterization(IEEE, 2007) Wygant, Ira O.; Jamal, Nafis S.; Lee, Hyunjoo J.; Nikoozadeh, Amin; Zhuang, Xuefeng; Oralkan, Ömer; Ergün, Arif Sanlı; Karaman, Mustafa; Khuri-Yakub, Butrus ThomasThe cost and complexity of medical ultrasound imaging systems can be reduced by integrating the transducer array with an integrated circuit (IC). By incorporating some of the system's front-end electronics into an IC, bulky cables and costly system electronics can be eliminated. Here we present an IC for 3D intracavital imaging that requires few electrical connections but uses a large fraction of a 16x16-element 2D transducer array to transmit focused ultrasound. To simplify the receive and data acquisition electronics, only the 32 elements along the array diagonals are used as receivers. The IC provides a preamplifier for each receiving element. Each of the 224 transmitting elements is provided an 8-bit shift register, a comparator, and a 25-V pulser. To transmit, a global counter is incremented from 1 to 224; each pulser fires when its stored register value is equal to the global count value. Electrical testing of the fabricated IC shows that it works as designed. The IC was flip-chip bonded to a two-dimensional capacitive micromachined ultrasonic transducer (CMUT) array. A two-dimensional image of a wire target phantom was acquired.Yayın Minimally redundant 2-D array designs for 3-D medical ultrasound imaging(IEEE-Inst Electrical Electronics Engineers Inc, 2009-07) Karaman, Mustafa; Wygant, Ira O.; Oralkan, Ömer; Khuri-Yakub, Butrus ThomasIn real-time ultrasonic 3-D imaging, in addition to difficulties in fabricating and interconnecting 2-D transducer arrays with hundreds of elements, there are also challenges in acquiring and processing data from a large number of ultrasound channels. The coarray (spatial convolution of the transmit and receive arrays) can be used to find efficient array designs that capture all of the spatial frequency content (a transmit-receive element combination corresponds to a spatial frequency) with a reduced number of active channels and firing events. Eliminating the redundancies in the transmit-receive element combinations and firing events reduces the overall system complexity and improves the frame rate. Here we explore four reduced redundancy 2-D array configurations for miniature 3-D ultrasonic imaging systems. Our approach is based on 1) coarray design with reduced redundancy using different subsets of linear arrays constituting the 2-D transducer array, and 2) 3-D scanning using fan-beams (narrow in one dimension and broad in the other dimension) generated by the transmit linear arrays. We form the overall array response through coherent summation of the individual responses of each transmit-receive array pairs. We present theoretical and simulated point spread functions of the array configurations along with quantitative comparison in terms of the front-end complexity and image quality.
