Yazar "Zahorian, Jaime" seçeneğine göre listele

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    An Analog beamformer for integrated high-frequency medical ultrasound imaging
    (IEEE, 2011) Gürün, Gökçe; Zahorian, Jaime; Tekeş, Coşkun; Karaman, Mustafa; Hasler, Paul E.; Değertekin, Fahrettin Levent
    We designed and fabricated a dynamic receive beamforming integrated circuit (IC) in 0.35-mu m CMOS technology. This beamformer is suitable for integration with an ultrasound annular array for high-frequency (30-50 MHz) intravascular ultrasound (IVUS) imaging. The beamformer IC is capable of buffering, delaying and preamplification for 8 receive channels. We explored an analog delay cell based on a currentmode first-order all-pass filter, which is used as the basic building block to form an analog dynamic delay line. We also explored a bandwidth enhancement method on the delay cell that improved the overall bandwidth of the delay line by a factor of 6. Each delay cell consumes 2.1 mW of power and is capable of generating a tunable delay between 1.75 ns to 2.5 ns, enabling dynamic receive beamforming over a focal range from 1.4 mm to 2 mm. We successfully integrated the fabricated beamformer IC with an 8-element annular array. Our experimental test results demonstrated the desired buffering, preamplification and delaying capabilities of the beamformer.
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    Annular CMUT arrays for side looking intravascular ultrasound imaging
    (IEEE, 2007) Zahorian, Jaime; Güldiken, Rasim Oytun; Gürün, Gökçe; Qureshi, Muhammad Shakeel; Balantekin, Müjdat; Değertekin, Fahrettin Levent; Carlier, Stephane; Şişman, Alper; Karaman, Mustafa
    Although side looking intravascular ultrasound (SL-IVUS) imaging systems using single element piezoelectric transducers set the resolution standard in the assessment of the extent of coronary artery disease, improvements in transducer performance are needed to perform harmonic imaging and high resolution imaging of vulnerable plaque. With their small channel count; annular arrays exploiting the inherent broad bandwidth of CMUTs and electronic focusing capability of integrated electronics provide a path for desired SL-IVUS imaging catheters. In this paper, we first describe the design, low temperature fabrication of an 8401 mu m diameter, 8 element CMUT annular array. Testing of the individual elements in oil shows a uniform device behavior with 100% fractional bandwidth around 20MHz without including the effects of attenuation and diffraction. We also present linear scan imaging results obtained on wire targets in oil, tissue and tissue mimicking phantoms using both unfocused and dynamically focused transducers. The results for axial and lateral resolution are in agreement predicted by the simulations and show the feasibility of this approach for high resolution SL-IVUS imaging.
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    Dual-annular-ring CMUT array for forward-looking IVUS imaging
    (IEEE, 2006) Güldiken, Rasim Oytun; Zahorian, Jaime; Balantekin, Müjdat; Değertekin, Fahrettin Levent; Tekeş, Coşkun; Şişman, Alper; Karaman, Mustafa
    We investigate a dual-annular-ring CMUT array configuration for forward-looking intravascular ultrasound (FL-IVUS) imaging. The array consists of separate, concentric transmit and receive ring arrays built on the same silicon substrate. This configuration has the potential for independent optimization of each array and uses the silicon area more effectively without any particular drawback. We designed and fabricated a 1mm diameter test array which consists of 24 transmit and 32 receive elements. We investigated synthetic phased array beamforming with a non-redundant subset (if transmit-receive element pairs of the dual-annular-ring array. For imaging experiments, we designed and constructed a programmable FPGA-based data acquisition and phased array beamforming system. Pulse-echo measurements along with imaging simulations suggest that dual-ring-annular array should provide performance suitable for real-time FLAVUS applications.
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    Experimental study of dual-ring CMUT array optimization for forward-looking IVUS
    (IEEE, 2011) Tekeş, Coşkun; Zahorian, Jaime; Gürün, Gökçe; Satir, Sarp; Hochman, Michael; Xu, Toby; Rashid, Muhammad Wasequr; Değertekin, Fahrettin Levent; Karaman, Mustafa
    Forward-looking (FL) catheters have guiding and volumetric imaging capacities which are highly desirable for IVUS applications. Large channel and firing counts have to be reduced to enable 3-D real-time imaging and simplify front-end electronics. Recently, we have proposed an optimization procedure for dual ring FL arrays which is based on finding an optimal coarray set using the simulated annealing algorithm. The presented algorithm is based on finding a predefined number of optimal firing set which results in elimination of redundant spatial frequencies in the coarray. In this study, we present the experimental demonstration of the proposed method with fabricated single chip CMUT on CMOS system based FL dual ring arrays. The dual ring CMUT arrays were monolithically fabricated on top of CMOS chips which have 25-V pulsers and low-noise transimpedance amplifiers for each transmit and receive array elements. The fabricated CMUT arrays have 56 transmit and 48 receive elements operating at 12 MHz with a 1.4 mm outer diameter. To test the imaging performance of the optimal reduced set, we obtained a 512-element coarray set from the full 2688-element set. In the experiment, we used a phantom of 100-mu m aluminium wires immersed in oil tank. We have reconstructed both 2-D PSFs and B-scan images of wire targets. Experimental results demonstrate that the simulated annealing based optimal firing set achieves acceptable lateral and contrast resolution performances with 1/5 of the full set.