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• Mulani, Sufayan; Ziksari, Mahsa Sotoodeh; Austeng, Andreas & Näsholm, Sven Peter (2026). Rectified wavenumber algorithms for efficient ultrasound imaging. Ultrasonics. ISSN 0041-624X. 168. doi: 10.1016/j.ultras.2026.108227. Fulltekst i vitenarkiv Vis sammendrag

  Wavenumber-domain beamforming offers substantial computational advantage over conventional time-domain algorithms in ultrasound image formation. However, these methods are found to introduce distortions at large angles and greater depths, making it nontrivial to replace conventional processing pipelines with wavenumber-domain approaches. This paper presents a wavenumber-domain framework that produces images consistent with conventional delay-and-sum (DAS) beamforming, while retaining the computational efficiency of Fourier-domain processing. Building on recent work on DAS-consistent imaging for multistatic acquisition data, the key utility of this novel algorithm is its applicability in plane-wave, focused-transmit, and diverging-wave imaging. The approach compensates for the implicit spatial-frequency filtering of earlier wavenumber-domain formulations through a modified Fourier-domain weighting and an axial scaling to the reconstructed image. Using data from simulations, phantom experiments, and in-vivo liver imaging, we demonstrate that the proposed method preserves DAS-equivalent amplitude, speckle statistics, resolution, and contrast. Quantitative image comparison confirms a close agreement between DAS and the proposed method with Structural Similarity (SSIM) values exceeding 0.99, whereas SSIM between earlier wavenumber-domain beamformers and DAS is lower, ranging from 0.67 to 0.92 depending on the transmit scheme. The proposed method yields approximately one order-of-magnitude reduction in computational cost compared to conventional DAS, making it well-suited for real-time and resource-constrained ultrasound systems.

• Jensen, Are Charles; Ziksari, Mahsa Sotoodeh; Austeng, Andreas & Näsholm, Sven Peter (2026). A Coherence-Restoring Subspace Projection for Adaptive Array Spectral Estimation. IEEE Access. 14, s. 37062–37071. doi: 10.1109/access.2026.3671486. Fulltekst i vitenarkiv Vis sammendrag

  Wide-beam or single-transmit acquisitions often reduce local spatial coherence, breaking the narrowband model assumed by high-resolution array spectral estimators such as IAA and Capon and thereby degrading performance. We propose a discrete prolate spheroidal sequence (DPSS) subspace projection of delay-focused aperture data. This projection suppresses incoherent off-angle energy and restores local spatial coherence, enabling scanline-wise adaptive spectral estimation under severe model mismatch. Each delay-focused aperture vector is projected onto a DPSS subspace spanned by the first K eigenvectors corresponding to a small angular bandwidth. The approach is lightweight, with precomputation and a per-point complexity of O(MK), and integrates naturally into standard delay-focused processing pipelines. Frequency–angle plots reveal how the projection reconstructs coherent ridge structures that are otherwise obscured by wide‑beam incoherence. Simulations in both plane-wave and diverging-wave ultrasound scenarios demonstrate improved resolution and contrast in single-transmit wide-beam imaging. Qualitative results on recorded channel data from the public PICMUS dataset provide an experimental sanity check and validation, indicating that the same coherence-restoration behavior is observed in real recordings. All experimental validation in this work is confined to ultrasound imaging; assessment of other array-processing applications is left for future work.

• Mulani, Sufayan Ikabal; Ziksari, Mahsa Sotoodeh; Austeng, Andreas & Näsholm, Sven Peter (2026). Delay-and-Sum Consistent Wavenumber Algorithm. IEEE Transactions on Ultrasonics. 73(3), s. 379–390. doi: 10.1109/tuson.2026.3667456. Fulltekst i vitenarkiv Vis sammendrag

  Fourier-domain beamforming methods offer a computationally efficient alternative to time domain methods in ultrasound imaging. Among these, the wavenumber algorithm (WA) achieves fast image reconstruction from full-matrix capture (FMC) data but introduces amplitude distortions due to its inherent weighting. In this study, we present a modified Fourier-domain beamforming method that operates on FMC data and reproduces the amplitude response of the conventional delay-and-sum (DAS) method while maintaining the computational efficiency of WA. This is achieved through a derivation of a correction factor that restores DAS-like amplitude characteristics in WA. The correction is implemented in two stages, consisting of a matrix multiplication to the data in the Fourier domain and a subsequent scaling with the z coordinate in the reconstructed image. Validation on simulated point targets, phantom experiment, and in-vivo imaging demonstrates that the proposed method produces images nearly indistinguishable from DAS but with significantly reduced computational burden. We also investigate the role of zero-padding, showing how interpolation accuracy affects reconstruction fidelity and computational efficiency. The proposed approach can, for example, facilitate the development of ultrasound systems with reduced power consumption.

• Ziksari, Mahsa Sotoodeh; Austeng, Andreas; Näsholm, Sven Peter; Cecconello, Elsa; Holm, Sverre & Karabiyik, Yücel (2024). Application of Spatial Autocorrelation in Experimental Time-Harmonic Elastography. IEEE International Symposium on Applications of Ferroelectrics (ISAF). ISSN 2375-0448. doi: 10.1109/UFFC-JS60046.2024.10793924. Fulltekst i vitenarkiv
• Ziksari, Mahsa Sotoodeh; Näsholm, Sven Peter; Austeng, Andreas & Jensen, Are Charles (2024). Enhancing Diverging-Wave Ultrasound Imaging with the Iterative Adaptive Approach. IEEE International Symposium on Applications of Ferroelectrics (ISAF). ISSN 2375-0448. doi: 10.1109/UFFC-JS60046.2024.10793849. Fulltekst i vitenarkiv
• Ziksari, Mahsa Sotoodeh; Austeng, Andreas; Näsholm, Sven Peter; Cecconello, Elsa; Holm, Sverre & Karabiyik, Yücel (2024). An Autocorrelation-Based Approach for Estimating Shear Wave Speed using 2D Velocity Vector. IEEE International Symposium on Applications of Ferroelectrics (ISAF). ISSN 2375-0448. doi: 10.1109/UFFC-JS60046.2024.10794020. Fulltekst i vitenarkiv

Se alle arbeider i NVA

• Ziksari, Mahsa Sotoodeh; Alix, Corentin; Austeng, Andreas; Salles, Sebastien Andre Roger & Karabiyik, Yücel (2026). Directional clutter filter imaging for time harmonic elastography. Fulltekst i vitenarkiv
• Mulani, Sufayan Ikabal; Ziksari, Mahsa Sotoodeh; Austeng, Andreas & Näsholm, Sven Peter (2025). A Modified Wavenumber Algorithm That Preserves the DAS Image. Fulltekst i vitenarkiv
• Mulani, Sufayan Ikabal; Ziksari, Mahsa Sotoodeh; Austeng, Andreas & Näsholm, Sven Peter (2025). Efficient Ultrasound Imaging by Integrating Refocus with Fourier Beamforming. Fulltekst i vitenarkiv
• Ziksari, Mahsa Sotoodeh; Austeng, Andreas; Näsholm, Sven Peter & Jensen, Are Charles (2025). Enhanced Diverging-Wave Iterative Adaptive Approach Beamforming using Spatial Subspace Filtering. Fulltekst i vitenarkiv
• Han, Chaoran; Boukraa, Mohamed Aziz; Näsholm, Sven Peter; Austeng, Andreas; Ziksari, Mahsa Sotoodeh & Karabiyik, Yücel (2025). A Simulation Framework for Ultrasound Time Harmonic Elastography (THE). Fulltekst i vitenarkiv
• Han, Chaoran; Ziksari, Mahsa Sotoodeh; Näsholm, Sven Peter; Austeng, Andreas; Cecconello, Elsa & Boukraa, Mohamed Aziz [Vis alle 8 forfattere av denne artikkelen] (2025). Shear-wave speed estimation in time harmonic elastography. Fulltekst i vitenarkiv
• Ziksari, Mahsa Sotoodeh; Näsholm, Sven Peter & Austeng, Andreas (2024). Adaptive beamforming for high frame-rate ultrasound imaging. Fulltekst i vitenarkiv
• Ziksari, Mahsa Sotoodeh; Näsholm, Sven Peter; Austeng, Andreas & Jensen, Are Charles (2024). Enhancing Diverging Wave Ultrasound Imaging with the Iterative Adaptive Approach. Fulltekst i vitenarkiv
• Ziksari, Mahsa Sotoodeh; Austeng, Andreas; Näsholm, Sven Peter; Cecconello, Elsa; Holm, Sverre & Karabiyik, Yücel (2024). Application of Spatial Autocorrelation in Experimental Time-Harmonic Elastography. Fulltekst i vitenarkiv
• Ziksari, Mahsa Sotoodeh; Austeng, Andreas; Näsholm, Sven Peter; Cecconello, Elsa; Holm, Sverre & Karabiyik, Yücel (2024). An Autocorrelation-Based Approach for Estimating Shear Wave Speed Using 2D Velocity Vector. Fulltekst i vitenarkiv

Se alle arbeider i NVA