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Session: Imaging - General
Session starts: Thursday 24 January, 10:40
Presentation starts: 11:10
Room: Lecture room 559

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Suzanne Leinders (Laboratory of Acoustical Wavefield Imaging, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft The Netherlands )
Wouter Westerveld (Optics Research Group, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands ;Nano-instrumentation Department Technical Sciences, TNO, Stieltjesweg 1, 2628 CK Delft, The Netherlands )
Jose Pozo (Nano-instrumentation Department Technical Sciences, TNO, Stieltjesweg 1, 2628 CK Delft, The Netherlands )
Mirvais Yousefi (Photonic Sensing Solutions, Amsterdam, The Netherlands )
Paul Urbach (Optics Research Group, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands)
Koen van Dongen (Laboratory of Acoustical Wavefield Imaging, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands )

Abstract:
Ultrasonography is a medical diagnostic tool utilized for the imaging of subcutaneous body structures, i.e. tendons, muscles, joints, vessels and internal organs for possible pathology or lesions. Lately, it has been recommended as an effective diagnostic tool for the diagnostic of atherosclerosis. By bringing the ultrasonic transducer, mounted on the tip of a catheter, into the artery an image of the vessel wall could be obtained. However, respiratory motion can displace the catheter tip as much as 6 mm, resulting in serious deterioration of images. To improve the image quality, it is advantageous to use an array of many transducers in the arterial direction [1,2]. Unfortunately, traditional piezo-electric receivers are relatively large (500 µm) and must be wired individually, which highly limits the amount of transducers that could be used to build an array. Therefore, alternative transducers or methods are needed. We propose a novel type of ultrasound receiver array based on integrated photonic resonators, in which photons rather than electrons, carry information. This technology allows for small footprint (~50 µm per sensor) and hence, for maximizing the amount of sensors in the catheter. One sensor consists of an optical resonator on a silicon substrate with an acoustical membrane that can be efficiently excited by an ultrasonic wave field. The deformation of the membrane caused by ultrasonic waves shifts the optical resonance[3], which can be monitored by an external interrogator system. Finite element modeling (COMSOL Multiphysics) has been performed to optimize the acoustical sensitivity of the receiver. Insight about the influence on the acoustical behavior of the size, thickness and shape of the membrane were obtained using both static and time domain analysis. The model predicts that for a 2.5 µm thick SiO2 circular membrane with 30 µm radius, 0.9 MHz resonance occurs when the receiver is submerged in water. The promising results shown by the simulations, lead to the conclusion that this technology is a suitable candidate for miniaturized ultrasound sensors. REFERENCES [1] R.S.C. Cobbold, Foundations of biomedical ultrasound, 2007. [2] E.J. Alles, et al. “An axial array for three-dimensional intravasular ultrasound”, IEEE International Ultrasonics Symposium, Dresden Germany (2012) [3] Wouter J. Westerveld, et al. "Characterization of a photonic strain sensor in silicon-on-insulator technology," Opt. Lett. 37, 479-481 (2012)