28 sonuçlar
Arama Sonuçları
Listeleniyor 1 - 10 / 28
Yayın Phased subarray imaging for low-cost, wideband coherent array imaging(IEEE, 2003) Johnson, Jeremy A.; Oralkan, Ömer; Ergün, Arif Sanlı; Demirci, Utkan; Karaman, Mustafa; Khuri-Yakub, Butrus ThomasThe front-end hardware complexity of conventional full phased array (FPA) imaging is proportional to the number of array elements. Phased subarray (PSA) imaging has been proposed as a method of reducing the hardware complexity-and therefore system cost and size-while achieving near-FPA image quality. A new method is presented for designing the subarray-dependent interpolation filters suitable for wideband PSA imaging. The method was tested experimentally using pulse-echo data of a wire target phantom acquired using a 3.2-cm. 128-element capacitive micromachined ultrasonic transducer (CMUT) array with 85% fractional bandwidth at 3 MHz. A specific PSA configuration using seven 32-element subarrays was compared to FPA imaging, representing a 4-fold reduction in front-end hardware complexity and a 43% decrease in frame rate. For targets near the fixed transmit focal distance, the mean 6-dB lateral resolution was identical to that of FPA, the axial resolution improved by 4%, and the SNR decreased by 5 dB. Measurements were repeated for 10 different PSA configurations with subarray sizes ranging from 4 to 60. The lateral and axial resolutions did not vary significantly with subarray size; both the SNR and contrast-to-noise ratio (CNR) improved with increased subarray size.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 CMUT-based volumetric ultrasonic imaging array design for forward looking ICE and IVUS applications(SPIE-Int Soc Optical Engineering, 2013) Tekeş, Coşkun; Zahorian, Jaime S.; Xu, Toby; Rashid, Muhammad Wasequr; Satır, Sarp; Gürün, Gökçe; Karaman, Mustafa; Hasler, Jennifer Olson; Değertekin, Fahrettin LeventDesigning a mechanically flexible catheter based volumetric ultrasonic imaging device for intravascular and intracardiac imaging is challenging due to small transducer area and limited number of cables. With a few parallel channels, synthetic phased array processing is necessary to acquire data from a large number of transducer elements. This increases the data collection time and hence reduces frame rate and causes artifacts due to tissue-transducer motion. Some of these drawbacks can be resolved by different array designs offered by CMUT-on-CMOS approach. We recently implemented a 2.1-mm diameter single chip 10 MHz dual ring CMUT-on-CMOS array for forward looking ICE with 64-transmit and 56-receive elements along with associated electronics. These volumetric arrays have the small element size required by high operating frequencies and achieve sub mm resolution, but the system would be susceptible to motion artifacts. To enable real time imaging with high SNR, we designed novel arrays consisting of multiple defocused annular rings for transmit aperture and a single ring receive array. The annular transmit rings are utilized to act as a high power element by focusing to a virtual ring shaped line behind the aperture. In this case, image reconstruction is performed by only receive beamforming, reducing total required firing steps from 896 to 14 with a trade-off in image resolution. The SNR of system is improved more than 5 dB for the same frequency and frame rate as compared to the dual ring array, which can be utilized to achieve the same resolution by increasing the operating frequency.Yayın 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 LeventWe 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.Yayın Damariçi yanal kesit görüntüleme için farklı prob yapılarının incelenmesi(IEEE, 2009-06-26) Şişman, Alper; Karaman, MustafaBu çalışmada dönen bir şaftın yanal yüzeyine yerleştirilmiş 8 adet içiçe halka elemanlardan oluşan yana bakan görüntüleme için yeni bir kateter yapısı incelenmiştir. Bu Katater mimarisi basit bir dizi önü alıcı verici elektroniği ile değişken odaklama olanağı sağlamaktadır. Önerilen mimari, mevcut iki farklı kateter mimarisiyle benzetim sonuçları ile karşılaştırmalı olarak incelenmiştir. Benzetimlerde görüntüleme kateter çapı 1mm alınmış, farklı derinlikler ve açılar için 3 noktasal yansıtıcı ile NDF çıkarılmıştır.Yayın 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, MustafaWe 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.Yayın 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, MustafaForward-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.Yayın Çok katmanlı düzlemsel ortam için termoakustik dalga denkleminin çözümü(IEEE, 2017-06-27) Bayıntır, Hazel; Ünalmış Uzun, Banu; İdemen, Mehmet Mithat; Karaman, MustafaBu çalışmada, farklı akustik parametrelere sahip çok katmanlı düzlemsel ortam için tüm katmanlarda kaynak dağılımı olduğu varsayımı altında termoakustik dalga denkleminin analitik olarak düz ve ters çözümü elde edilmiştir. Çok katmanlı düzlemsel ortam için elde edilen analitik çözüm katmanlı düzlemsel green fonksiyonlarına dayanmaktadır. Çok katmanlı düzlemsel modelleme meme, deri ve karın bölgesi görüntülemelerine uygun bir modellemedir. Elde edilen analitik çözüm ile literatürde var olan homojen ortam varsayımına dayanan çözüm her katmanda noktasal kaynak alınarak sayısal olarak karşılaştırılmıştır.Yayın Damar içi öne bakan ultrasonik görüntüleme için eşdeğer dizi örnekleme yöntemleri(IEEE, 2009-06-26) Tekeş, Coşkun; Karaman, MustafaDamar içi öne bakan ultrasonik görüntüleme gerçek zamanlı hacimsel (üç boyutlu) görüntülemeye imkan vermesi bakımından yaygın olarak kullanılmaktadır. Damar içi görüntülemede fiziksel boyutların küçük olması nedeniyle alıcı-verici kanal sayısı çok sınırlanmakta ve dolayısıyla yapay evreli dizi teknikleri kullanılmaktadır. Öte yandan, harekete bağlı görüntü bozukluklarını azaltmak için işaret gönderme alma adım sayısının azaltılması gerekmektedir. Bu, eşdeğer dizideki fazlalık frekans bileşenleri azaltılarak sağlanabilir. Bu çalışmada, eşdeğer dizideki fazlalık frekans bileşenlerinin azaltılmasına dayalı farklı örnekleme teknikleri incelenmiştir. Bu tekniklerin görüntü kalitesi 64 elemanlı bir halkasal dizinin asıl ve kontrol eşdeğer dizileri referans alınarak karşılaştırmalı olarak irdelenmiştir. Benzetim sonuçları 64 elemanlı bir halka dizi için 2049 asıl küme, 350 azaltılmış küme 40 dB içinde eşdeğer performans vermektedir.Yayın Subarray delta-sigma beamforming for ultrasonic imaging(IEEE, 2002) Bilge, Hasan Şakir; Karaman, MustafaWe present a beamforming architecture based on subarray processing with non-uniform oversampling 1-bit delta-sigma (??) modulation. The subarray processing combines conventional phased array and synthetic aperture approaches to form a large aperture using small subarrays thus reduces active channel count. ??-based beamforming improves the efficiency of front-end processing further: oversampling permits precise delaying and single bit data processing simplifies beamforming operation. To reduce the number of firings we use a low beam density associated with the subarray size, and then increase the beam density by lateral interpolation prior to coherent beam summation. Our experimental test results show that the proposed scheme provides high-resolution beamforming while simplifying the front-end.
- «
- 1 (current)
- 2
- 3
- »
