Sabiq Muhtadi;Keita A. Yokoyama;Caterina M. Gallippi
{"title":"Double Profile Intersection (DoPIo) Ultrasound With Acoustic Radiation Force Tilting Interrogates Young’s Modulus in Transversely Isotropic Media: An In Silico Study","authors":"Sabiq Muhtadi;Keita A. Yokoyama;Caterina M. Gallippi","doi":"10.1109/OJUFFC.2025.3613275","DOIUrl":"https://doi.org/10.1109/OJUFFC.2025.3613275","url":null,"abstract":"This study evaluates the potential for interrogating the Young’s elastic moduli in anisotropic media, including tissue, using Double Profile Intersection (DoPIo) ultrasound. DoPIo is an on-axis acoustic radiation force (ARF)-based elasticity imaging method that quantifies shear elasticity without relying on shear wave propagation. It is hypothesized that by applying a range of ARF excitations that are not perpendicular to the axis of symmetry (AoS) of transversely isotropic (TI) materials and monitoring the resultant variation in DoPIo-measured elasticity versus excitation angle, the Young’s elastic modulus may be interrogated in addition to the shear elastic modulus. The hypothesis was tested in silico, and results suggested that while DoPIo outcomes measured at normal (90°) ARF-AoS incidence were related to the shear elastic modulus alone, variation in DoPIo-derived elasticity over ARF-AoS incidence angle (defined as <inline-formula> <tex-math>$Delta textit {Elasticity}$ </tex-math></inline-formula>) exhibited a strong linear correlation with the longitudinal Young’s modulus (<inline-formula> <tex-math>${E}_{L}$ </tex-math></inline-formula>). The results suggest that <inline-formula> <tex-math>${E}_{L}$ </tex-math></inline-formula> evaluated by the rate of change of <inline-formula> <tex-math>$Delta textit {Elasticity}$ </tex-math></inline-formula> with ARF-AoS incidence angle may serve as a novel biomarker for characterizing elastically anisotropic tissues such as kidney, skeletal muscle, and breast.","PeriodicalId":73301,"journal":{"name":"IEEE open journal of ultrasonics, ferroelectrics, and frequency control","volume":"5 ","pages":"161-165"},"PeriodicalIF":2.9,"publicationDate":"2025-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=11176129","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145210158","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Mingyang Wang;Jeffrey S. Orringer;Yannis M. Paulus;Xinmai Yang;Xueding Wang
{"title":"Photo-Mediated Ultrasound Therapy (PUT) for the Treatment of Deep Cutaneous Vasculature","authors":"Mingyang Wang;Jeffrey S. Orringer;Yannis M. Paulus;Xinmai Yang;Xueding Wang","doi":"10.1109/OJUFFC.2025.3604391","DOIUrl":"https://doi.org/10.1109/OJUFFC.2025.3604391","url":null,"abstract":"Traditionally, pulsed dye laser (PDL) therapy has been used to treat cutaneous blood vessels in patients with port-wine stain (PWS) birthmarks. PDL therapy, however, has limited treatment depth, and frequently results in suboptimal therapeutic outcomes when used to treat deep cutaneous blood vessels. We have developed photo-mediated ultrasound therapy (PUT), a hybrid cavitation-based anti-vascular technology combining nanosecond light pulses with ultrasound bursts and demonstrated its great potential in treating deep cutaneous vessels. This study explored the feasibility of PUT as an alternative to traditional PDL therapy for deep cutaneous vascular treatment in a clinically relevant chicken wattle model. PUT was employed to induce cavitation in blood vessels by using different light fluence and ultrasound pressure combinations. Theoretical modeling and in vitro experiments were first conducted to validate and optimize parameters for PUT treatment targeting deep vasculature. PUT treatments were then performed in a chicken wattle model using an experimental setup, and outcomes were assessed by using polarized dermoscope, optical coherence tomography angiography (OCT-A) imaging, and histopathological analyses. The results demonstrated that PUT can effectively penetrate the entire thickness of chicken wattle tissue, which is about 3 mm, and significantly reduce blood vessel density by 45.20% with a light fluence 10–100 times less than the fluence used in traditional PDL therapy. OCT-A imaging showed that local blood perfusion was significantly reduced, and the reduced blood perfusion persisted for at least 7 days post-treatment in the treated areas. Histopathological analyses based on H&E, CD31, and Russell-Movat Pentachrome (RMP) stains confirmed effective and selective vascular damage through the entire thickness of chicken wattle without causing collateral thermal damage. In conclusion, PUT can effectively eliminate blood vessels with a treatment depth up to 3 mm whereas the 3 mm treatment depth demonstrated in this study was only limited by the chicken wattle model. By leveraging the deep tissue penetration of ultrasound and the flexibility in treatment parameter selection, PUT can effectively treat deep cutaneous vasculature using reduced light fluence and thereby minimize collateral damage in skin tissues. Thus, PUT holds great potential for treatment of cutaneous vascular anomalies such as PWS.","PeriodicalId":73301,"journal":{"name":"IEEE open journal of ultrasonics, ferroelectrics, and frequency control","volume":"5 ","pages":"135-145"},"PeriodicalIF":2.9,"publicationDate":"2025-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=11145956","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145036877","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yu Weng;Luke Coulter;Muhammad Saad Khan;Eno Hysi;Agata A. Exner;Michael C. Kolios
{"title":"Cross Amplitude Modulation and Compound Amplitude Modulation for Nonlinear Contrast-Enhanced Ultrasound Imaging of Nanobubbles","authors":"Yu Weng;Luke Coulter;Muhammad Saad Khan;Eno Hysi;Agata A. Exner;Michael C. Kolios","doi":"10.1109/OJUFFC.2025.3603792","DOIUrl":"https://doi.org/10.1109/OJUFFC.2025.3603792","url":null,"abstract":"In nonlinear contrast-enhanced ultrasound (CEUS) imaging, nanobubbles (NBs) offer a promising alternative for enhanced visualization of microvascular structures and molecular imaging. This study explores two amplitude-modulated (AM) techniques—cross amplitude modulation (xAM) and compound amplitude modulation (cAM)—to enhance the capabilities of NB-mediated CEUS imaging. Both methods were tested on the Vevo F2 ultrasound imaging system (Fujifilm VisualSonics Inc.) using the Vevo Advanced Data Acquisition (VADA) mode, allowing full customization of pulse sequences. The xAM technique utilized a three-event pulse sequence that transmits cross-propagating plane-wave beams from dual apertures. This method isolated nonlinear scattered waves from NBs, reducing background noise and enhancing image quality. In contrast, cAM achieved a high frame rate of 706 Hz, a valuable feature for tracking the NB vascular flow dynamics. cAM combined plane-wave compounding with amplitude modulation, transmitting two events (half- and full-amplitude), achieving high frame rates for velocity imaging at the expense of image quality. NBs at a concentration of <inline-formula> <tex-math>$10^{9}$ </tex-math></inline-formula> NBs/mL, intended to mimic estimated in vivo post-injection concentrations, were injected into custom-built tissue-mimicking vessel phantoms. Experiments demonstrated that xAM significantly improved the contrast-to-noise ratio (CNR) and contrast-to-tissue ratio (CTR) by over 10 times compared to B-mode imaging, especially at larger steering angles. Conversely, cAM’s CNR and CTR were at least 50% lower than that of xAM, but it achieved a frame rate over 100 times faster than xAM. These results suggest xAM can enhance imaging clarity, while cAM offers high frame rates for velocity imaging, providing an imaging framework for preclinical and clinical applications.","PeriodicalId":73301,"journal":{"name":"IEEE open journal of ultrasonics, ferroelectrics, and frequency control","volume":"5 ","pages":"146-160"},"PeriodicalIF":2.9,"publicationDate":"2025-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=11143226","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145073325","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Archita Hati;Marco Pomponio;Nicholas V. Nardelli;Tanner Grogan;Kyungtae Kim;Dahyeon Lee;Jun Ye;Tara M. Fortier;Andrew Ludlow;Craig W. Nelson
{"title":"Radio Frequency From Optical With Instabilities Below 10-15-Generation and Measurement","authors":"Archita Hati;Marco Pomponio;Nicholas V. Nardelli;Tanner Grogan;Kyungtae Kim;Dahyeon Lee;Jun Ye;Tara M. Fortier;Andrew Ludlow;Craig W. Nelson","doi":"10.1109/OJUFFC.2025.3596866","DOIUrl":"https://doi.org/10.1109/OJUFFC.2025.3596866","url":null,"abstract":"This paper presents a frequency synthesis that achieves exceptional stability by transferring optical signals to the radio frequency (RF) domain at 100 MHz. We describe and characterize two synthesis chains composed of a cryogenic silicon cavity-stabilized laser at 1542 nm and an ultra-low expansion (ULE) glass cavity at 1157 nm, both converted to 10 GHz signals via Ti:Sapphire and Er/Yb:glass optical frequency combs (OFCs). The 10 GHz microwave outputs are further divided down to 100 MHz using a commercial microwave prescaler, which exhibits a residual frequency instability of <inline-formula> <tex-math>$sigma _{y}({1}~text {s})lt {10}^{-{15}}$ </tex-math></inline-formula> and low 10-18 level at a few thousand seconds. Measurements are performed using a newly developed custom ultra-low-noise digital measurement system and are compared to the carrier-suppression technique. The new system enables high-sensitivity evaluation across the entire synthesis chain, from the optical and microwave heterodynes as well as the direct RF signals. Results show an absolute instability of <inline-formula> <tex-math>${sigma }_{y}({1}~text {s})~approx ~{4.7}times {10}^{-{16}}$ </tex-math></inline-formula> at 100 MHz. This represents the first demonstration of such low instability at 100 MHz, corresponding to a phase noise of −140 dBc/Hz at a 1 Hz offset and significantly surpassing earlier systems. These advancements open new opportunities for precision metrology and timing systems.","PeriodicalId":73301,"journal":{"name":"IEEE open journal of ultrasonics, ferroelectrics, and frequency control","volume":"5 ","pages":"127-134"},"PeriodicalIF":2.9,"publicationDate":"2025-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=11121396","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144880475","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Vahid M. Safarzadeh;Konstantina Papangelopoulou;Marta Orlowska;Hans Dierckx;Jan D’Hooge
{"title":"Automated Measurement of Local Mechanical Activation on High Frame Rate Echocardiography","authors":"Vahid M. Safarzadeh;Konstantina Papangelopoulou;Marta Orlowska;Hans Dierckx;Jan D’Hooge","doi":"10.1109/OJUFFC.2025.3596042","DOIUrl":"https://doi.org/10.1109/OJUFFC.2025.3596042","url":null,"abstract":"High Frame Rate Speckle Tracking Echocardiography (HFR-STE) offers a method to pinpoint the local onset of contraction in the left ventricle (LV) and generate mechanical activation maps. In this paper, a new patient-specific spatiotemporal approach is proposed to identify activation times on left ventricular strain rate (SR) curves automatically. Curves are collected from 2D HFR-STE according to the 16-segment model. Using a Locally Weighted Principal Component Analysis (LWPCA), the main pattern of each segment’s SR curve is extracted locally. The first positive-to-negative zero-crossing point on the first principal component is identified as the activation time. Validation with a dataset of 40 subjects (20 healthy volunteers and 20 patients) showed that 94% of estimated activation times closely matched the expert-identified times, differing by no more than 16ms. Quantitative and qualitative comparisons between LWPCA and (weighted) averaging are also reported. Also, the automatically generated activation maps closely resemble their manually created counterparts, demonstrating good visual similarity.","PeriodicalId":73301,"journal":{"name":"IEEE open journal of ultrasonics, ferroelectrics, and frequency control","volume":"5 ","pages":"123-126"},"PeriodicalIF":2.9,"publicationDate":"2025-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=11113317","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144867646","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Volumetric Estimation of the Backscatter Coefficient With a Matrix Probe","authors":"Valentin Mazellier;François Varray;Pauline Muleki-Seya","doi":"10.1109/OJUFFC.2025.3588811","DOIUrl":"https://doi.org/10.1109/OJUFFC.2025.3588811","url":null,"abstract":"Evaluation of the backscatter coefficient (BSC) from soft tissues has many applications for medical diagnosis. However, electronic noise and spatial variations often affect BSC estimation, requiring spatial averaging inside a region of interest (ROI) that reduces spatial resolution compared to the B-mode images. This study explores 3D BSC estimation using a matrix probes to address this trade-off by allowing narrower ROIs without losing robustness. A comparison study between a 1024-element matrix probe (V8) and two linear probes (L12-5, L22-8) was made on homogeneous agar-based phantoms with Orgasol particles (5, 10, and <inline-formula> <tex-math>$20~mu $ </tex-math></inline-formula>m). BSC was computed using the reference phantom method, and robustness was assessed via the BSC standard deviation across ROIs. Results showed that, despite the lower B-mode resolution and longer correlation length between A-lines, volumetric estimation with a matrix probe offered comparable accuracy while enhancing robustness and resolution in the BSC map compared to the standard 2D estimation. These results could be beneficial for the analysis of complex heterogeneous media.","PeriodicalId":73301,"journal":{"name":"IEEE open journal of ultrasonics, ferroelectrics, and frequency control","volume":"5 ","pages":"119-122"},"PeriodicalIF":0.0,"publicationDate":"2025-07-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=11079648","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144680840","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Sophie V. Heymans;Marcus Ingram;Bram Carlier;Brecht Vandenborre;Marc Fournelle;Alessandro Ramalli;François Rottenberg;Koen van den Abeele;Jan D'Hooge
{"title":"Volumetric Passive Ultrasound Localization Microscopy of Radiation-Induced Nanodroplet Vaporization With a Large Aperture Matrix Array","authors":"Sophie V. Heymans;Marcus Ingram;Bram Carlier;Brecht Vandenborre;Marc Fournelle;Alessandro Ramalli;François Rottenberg;Koen van den Abeele;Jan D'Hooge","doi":"10.1109/OJUFFC.2025.3577590","DOIUrl":"https://doi.org/10.1109/OJUFFC.2025.3577590","url":null,"abstract":"Superheated nanodroplets (NDs) are proposed for in vivo radiation dose sensing applications, based on their ability to vaporize into echogenic microbubbles when exposed to ionizing radiation. Combined with Ultrasound Localization Microscopy (ULM), the ultrafast detection of radiation-induced ND vaporization produces super-resolved vaporization maps that match the radiation field with sub-millimeter accuracy. However, in the presence of flow, discriminating between microbubbles moving in the field of view and radiation-induced vaporization events is not trivial. As an alternative, sparse acoustic signatures emitted by vaporizing NDs can be super-localized by passive ULM, i.e. P-ULM. In this work, we extend our previous 2D implementation of P-ULM to 3D, using a large aperture matrix array probe. We exposed perfluorobutane NDs to a proton beam and recorded their vaporization signatures during irradiation. The events were extracted from the radiofrequency channel data using a spatiotemporal filtering approach and super-localized by fitting the time differences of arrival between channels to a one-way time of flight model. The vaporization maps were overlaid on the proton beam distribution and estimated the proton range and beam dispersion within <inline-formula> <tex-math>$0.98~pm ~0.04$ </tex-math></inline-formula> mm and <inline-formula> <tex-math>$0.03~pm ~0.02$ </tex-math></inline-formula> mm of the reference range measurement (depth-dose distribution in water measured with a diode), respectively. These results pave the way for volumetric dose mapping using radiosensitive nanodroplets and passive imaging.","PeriodicalId":73301,"journal":{"name":"IEEE open journal of ultrasonics, ferroelectrics, and frequency control","volume":"5 ","pages":"108-113"},"PeriodicalIF":0.0,"publicationDate":"2025-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=11027146","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144281284","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"The Impact of Valve Stenosis and Replacement on Wave Characteristics in Cardiac Shear Wave Elastography","authors":"Laurine Wouters;Lennert Minten;Marta Orlowska;Annette Caenen;Jürgen Duchenne;Jens-Uwe Voigt;Jan D’Hooge","doi":"10.1109/OJUFFC.2025.3577142","DOIUrl":"https://doi.org/10.1109/OJUFFC.2025.3577142","url":null,"abstract":"Cardiac shear wave elastography (SWE) is a non-invasive technique to assess myocardial stiffness, based on the speed of waves that travel through the heart after valve closure. The wave physics underlying natural SWE remains incompletely understood. Therefore, we investigated the impact of wave excitation sources on 3 wave propagation aspects – wave amplitude (determined as wave acceleration magnitude), temporal wave width and speed. SWE was applied to 17 patients with aortic stenosis (AS), 13 AS patients that underwent transcatheter aortic valve implantation (TAVI), 10 AS patients that underwent surgical aortic valve replacement (AVR) and 18 age-matched healthy volunteers (HV). Absolute wave acceleration was lower in AS, TAVI and AVR patients compared to HV (1.5±0.60 vs 2.8±1.1 m/s2; p=0.001; 1.6±0.78 vs 2.8±1.1 m/s2; p=0.010; 1.7±0.66 vs 2.8±1.1 m/s2; p=0.015). Wave acceleration amplitude (measured as negative peak acceleration of the tissue) correlated with wave speed (r=0.388; p=0.003), implying that absolute wave acceleration is smaller in a stiffer heart. Subgroup analysis showed that the correlation between wave peak acceleration and speed is less steep in AS patients vs. HV (slopes: 0.23 vs 0.47 s). This implies that stenotic valves generate a wave with a lower acceleration magnitude compared to native valves. Further, temporal wave width was lower in TAVI patients vs. HV (8.7±2.3 vs 12.5±3.0 ms; p=0.002) and there was no difference in wave speed after aortic valve closure (AVC) between the groups. To conclude, wave acceleration magnitude and width offer additional insights into SWE physics next to wave speed and should be verified in a larger cohort.","PeriodicalId":73301,"journal":{"name":"IEEE open journal of ultrasonics, ferroelectrics, and frequency control","volume":"5 ","pages":"114-118"},"PeriodicalIF":0.0,"publicationDate":"2025-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=11027079","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144492373","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"IEEE OPEN JOURNAL OF ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL","authors":"","doi":"10.1109/OJUFFC.2025.3541756","DOIUrl":"https://doi.org/10.1109/OJUFFC.2025.3541756","url":null,"abstract":"","PeriodicalId":73301,"journal":{"name":"IEEE open journal of ultrasonics, ferroelectrics, and frequency control","volume":"5 ","pages":"C2-C2"},"PeriodicalIF":0.0,"publicationDate":"2025-06-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=11026032","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144219708","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Håvard Kjellmo Arnestad;Andreas Austeng;Sven Peter Näsholm
{"title":"Construction of Orthogonal Transmit Sequences Using the Nearest Orthogonal Matrix","authors":"Håvard Kjellmo Arnestad;Andreas Austeng;Sven Peter Näsholm","doi":"10.1109/OJUFFC.2025.3576722","DOIUrl":"https://doi.org/10.1109/OJUFFC.2025.3576722","url":null,"abstract":"A wide variety of transmit sequences can be employed in medical ultrasound, including plane waves, diverging waves, and focused beams. The choice of sequence often involves trade-offs between resolution, signal-to-noise ratio (SNR), frame rate, and harmonic imaging capabilities. However, the desirable mathematical property of orthogonality (i.e., absence of cross-talk) between transmits has generally received less attention. This property, often lacking, becomes particularly relevant for the recent REFoCUS (retrospective encoding for conventional ultrasound sequences) technique, which we in this work connect to the array signal processing technique called beamspace processing. Given an arbitrary transmit sequence, REFoCUS enables the recovery of signals from single-element transmissions (known as the multistatic dataset) thereby enhancing beamforming flexibility. In this context, the choice of transmit sequence influences the recovery process when using the intuitively appealing and computationally efficient adjoint-based method, which must be replaced by a regularized pseudoinverse for general applicability. In the current work, we derive the “closest” alternative to any chosen transmit sequence that makes the regularized and adjoint methods yield equal estimates of the multistatic dataset, and show via numerical experiments a reduction in beam and/or element cross-talk. The derivation is based on a matrix nearness problem of finding the nearest orthogonal (or unitary) matrix to the encoding matrix using singular value decomposition (SVD). The resulting transmit sequences offer a time-domain equivalent understanding of the regularized REFoCUS method, as well as a solution for optimizing the invertibility of ultrasound sequences.","PeriodicalId":73301,"journal":{"name":"IEEE open journal of ultrasonics, ferroelectrics, and frequency control","volume":"5 ","pages":"103-107"},"PeriodicalIF":0.0,"publicationDate":"2025-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=11023854","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144264239","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}