Browsing by Author "Zangabad, R. P."

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Mutual radiation impedance of circular CMUTs on a cylinder
(IEEE, 2016) Zangabad, R. P.; Bozkurt, A.; Yaralıoğlu, Göksen Göksenin; Bosch, J. G.; Soest, G. van; Steen, A. F. W. van der; Electrical & Electronics Engineering; YARALIOĞLU, Göksen Göksenin
In ultrasound imaging, cross coupling of transducer elements through the medium has significant effect on the frequency response, thus affecting the quality of the ultrasound image. In Side-Looking Intravascular Ultrasound (SL-IVUS) imaging a radial image of the vessel wall is formed using a transducer array in a cylindrical configuration. Recent advances in Capacitive Micromachined Ultrasound Transducer (CMUT) fabrication and integration techniques led to realization of CMUT arrays that can be wrapped into a cylinder shape and mounted on a catheter tip. In this paper, we present the calculation of radiation impedance of un-collapse CMUT arrays on a planar rigid baffle and on a cylinder using Finite Element Method (FEM) simulation. We link the crosstalk between planar CMUT elements with dips in frequency spectrum from experimental data and conclude that decreasing the cylinder radius causes downshift of the dips in frequency response. In the case of our device, these changes are too small to have detrimental effects on the array bandwidth.
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Signal to noise ratio optimization for a CMUT based medical ultrasound imaging system
(IEEE, 2015) Zangabad, R. P.; Bozkurt, A.; Yaralıoğlu, Göksen Göksenin; Electrical & Electronics Engineering; YARALIOĞLU, Göksen Göksenin
CMUTs offers key performance benefits compared to their piezoelectric counterparts. However, CMUTs are not widely adopted in commercial ultrasound imaging systems due to low signal to noise ratio (SNR) in the obtained images. Tunable parameters of the CMUT include the membrane material, radius, thickness, gap height, electrode size, and bias voltage. The aim of this work is to optimize these parameters to provide a solution for low SNR problem of CMUTs. In medical imaging, the device will be used in pulse echo mode for which both good receive sensitivity and high output pressure is required. Optimizing these performance metrics will end up in conflicting design parameters, such as a high gap for large pressure output whereas a small gap for better receive sensitivity. In this work, we develop a methodology for the investigation of the round-trip behavior of the transducer and try to co-optimize transmit and receive characteristics of the device to maximize the SNR of the received signal by tuning the bias voltage.