https://scholar.dgist.ac.kr/handle/20.500.11750/11752 2026-11-11T11:09:12Z https://scholar.dgist.ac.kr/handle/20.500.11750/61155 Title: SCORE beamforming: Spectral COherence REfinement for high-contrast ultrafast Doppler imaging Author(s): Guezzi, Nizar; Lee, Sangheon; Nam, Sangwoo; Seo, Youngho; Kim, Myeongchan; Eom, Kisang; Hyun, Jung Ho; Yu, Jaesok Abstract: Delay-and-sum (DAS) beamforming is widely used in ultrasound flow imaging due to its computational simplicity; however, its high sidelobe levels significantly degrade image contrast. Coherence factor (CF) beamforming partially alleviates this limitation by emphasizing spatial coherence, yet residual incoherent energy remains and continues to impair image quality. In this study, we propose a dual-stage beamforming approach that integrates CF weighting with a frequency-domain filtering stage designed to discriminate and suppress incoherent energy while preserving coherent signal components. The proposed method, termed SCORE (Spectral COherence REfinement), introduces an additional coherence-based discrimination mechanism beyond conventional CF beamforming. Simulation experiments involving single-target, multi-target, and vascular scenarios demonstrate that SCORE achieves substantial sidelobe suppression while maintaining signal integrity. In vivo validation using an open-source contrast-enhanced rat brain and kidney dataset, as well as contrast-free human spleen further confirms improved flow detectability, reduced background noise, and enhanced power Doppler imaging performance, as evidenced by increases in SNR and CNR approaching 10 dB compared to CF and GCF beamforming. Overall, the SCORE beamformer provides a robust framework for high-contrast vascular ultrasound imaging, offering superior sidelobe and noise suppression relative to DAS, CF and GCF. To enhance computational efficiency, the beamforming pipeline was implemented on a graphics processing unit (GPU) using an optimized CUDA framework, achieving real-time beamforming performance with processing times below 30 ms per frame. 2026-12-31T15:00:00Z https://scholar.dgist.ac.kr/handle/20.500.11750/60980 Title: Silicon photonic MEMS platform-based air-coupled optomechanical ultrasound receiver at 2.8 MHz with an ultra-compact active acoustic sensing area Author(s): Nam, Sangwoo; Kim, Jae Hyeon; Park, Young Jae; Choi, Dongju; Kim, Dong Uk; Guezzi, Nizar; Lee, Sangheon; Seo, Younghoon; Choi, Suyoung; Kim, Myeongchan; Seong, Hyojin; Lee, Changho; Ahn, Changmin; Kim, Jungwon; Yu, Jaesok; Han, Sangyoon Abstract: High-resolution non-contact non-destructive evaluation (NDE) utilizing MHz-range ultrasound in air-coupled environments faces two significant challenges: severe signal attenuation and reduced sensitivity due to transducer miniaturization. Optical ultrasound sensors have emerged as promising candidates to overcome these limitations; however, widespread adoption remains challenging. Conventional discrete optical sensors are limited by complex fabrication and rigid form factors. Furthermore, the efforts to implement these on photonic integrated circuits (PICs)-while addressing scalability-are typically constrained by limited sensitivity. To address these requirements, we report a chip-scale optomechanical ultrasound receiver implemented, for the first time, on a silicon photonics MEMS platform. This platform facilitates CMOS-compatible scalability and design freedom to independently optimize mechanical components and optical sensitivity. Consequently, the receiver demonstrates a compact active acoustic sensing area of 4 & times; 10-4 mm2. Despite this size reduction, in the noise-equivalent pressure (NEP)-active-area comparison, the proposed receiver's measured and estimated NEP values are positioned within a range comparable to or lower than those for previously reported air-coupled optical and CMUT sensors, when interpreted relative to the ideal area-scaling trend. Designed for a 2.8 MHz mechanical resonance, the receiver was benchmarked against a commercial 1 MHz air-coupled PZT transducer to provide a practical, controlled experimental baseline. In this controlled experimental comparison, the receiver showed a more than 25,000-fold higher received response per unit active acoustic area than the PZT baseline, serving as a complementary metric for unit-area received response and structural scaling potential. These findings suggest that the silicon photonic MEMS platform can provide a route toward compact, dense-array-compatible optical ultrasound receivers for localized air-coupled sensing. 2026-08-31T15:00:00Z https://scholar.dgist.ac.kr/handle/20.500.11750/60564 Title: 민감도 및 동적 영역이 조절 가능한 광기계 초음파 센서 및 그 제어 방법 Author(s): 남상우; 유재석; 한상윤; 최동주 Abstract: 본 개시는 초음파 센서 및 그 동작 방법에 관한 것으로서, 더욱 상세하게는 캔틸레버 구조의 멤브레인의 초기 위치를 조절하여 민감도 및 동적 영역이 조절 가능한 광기계 초음파 센서 및 그 제어 방법에 관한 것이다. https://scholar.dgist.ac.kr/handle/20.500.11750/60227 Title: Toward virtual bladder: real-time bladder volume monitoring with flexible AuCNT strain sensors Author(s): Cho, Youngjun; Jo, Yujin; Kang, Minseok; Shin, Heejae; Cho Jeongmok; Jeong Hyunghwa; Suh Hyunsuk Peter; Pak Changsik John; Park, Jeonhyeong; Kwon Soonchul; Choi Hongsoo; Yu, Jaesok; Kim, Hoe Joon; Lee, Sanghoon Abstract: Digital twin technology holds considerable potential for personalized diagnostics and treatment of bladder dysfunction, particularly neurogenic conditions such as underactive bladder (UAB). In this study, to address the need for precise monitoring, we introduce a flexible, stretchable strain sensor composed of gold-coated carbon nanotubes (AuCNTs) embedded in Ecoflex. We specifically designed a three-channel configuration to capture anisotropic expansion and evaluated the sensor's performance using both two-dimensional balloon models and ex-vivo three-dimensional porcine bladder models. As a result, the AuCNT sensor demonstrated high sensitivity, and the three-channel design significantly enhanced spatial accuracy compared to single-channel approaches. Based on these measurements, we created a preliminary "Virtual Bladder" model that provides dynamic, real-time visualization of bladder volume changes. While our current model requires further development to incorporate multimodal data and anatomical variability, it serves as a foundational step towards developing advanced digital twin frameworks and closed-loop neuromodulation systems for bladder dysfunction. 2025-12-31T15:00:00Z