• Ultrasound imaging is widely used in various clinical applications due to its non-invasive nature and real-time imaging capabilities. To enhance spatial resolution, high-frequency ultrasound imaging (>30 MHz) has been developed and applied in specialized areas such as ophthalmology, dermatology, and small animal research. However, conventional high frequency ultrasound imaging typically employs a line-by-line scanning method, which captures only a few tissue signal samples over a given period. This limitation significantly reduces the frame rate, particularly hindering the tracking of dynamic tissue motion—such as blood flow and shear wave propagation. To overcome this challenge, ultrafast ultrasound imaging has been introduced. This technique enables high-frame-rate imaging and has shown promise in applications such as small vessel blood flow mapping and ultrasonic shear wave elastography. In this presentation, I will present our integrated approach that combines high-frequency ultrasound with ultrafast imaging. I will explore advanced imaging techniques including super-resolution blood flow imaging and high-resolution ultrasound elastography. Specific applications will be discussed, including elastography and blood flow mapping in mouse brain, elastography of the eye and human tendons, and vector Doppler imaging for mapping small peripheral vessels in humans.

  • Genetically encoded gas vesicles provide an alternative to light for deep tissue cellular imaging. For this technology to be used to its fullest, the collaboration between chemical engineering and applied physics must continue so that biologists can visualize and track cells on an organ scale. In this talk, I will review the development of a contrast-enhanced imaging paradigm based on the transmission of supersonic X-waves. This approach culminated in the introduction of nonlinear sound-sheet microscopy (NSSM), a three-dimensional high-frequency method that sweeps thin ultrasound sheets through biological tissues labeled with contrast agents.

    NSSM relies on the transmission of cross-propagating plane waves that intersect along thin tissue sections referred to as sound sheets. At the intersection of the two waves, acoustic pressure is doubled. The full NSSM sequence consists in subsequently probing the medium with single plane wave transmissions. In doing so, ultrasound contrast agents experience a modulation of acoustic pressure if and only if they are located within the sound sheet plane.
    This amplitude modulation approach based on the geometric interaction of two wavefronts was developed to decouple nonlinear effects arising from wave propagation and nonlinear scattering of ultrasound contrast agents, and achieve highly imaging of microbubbles or gas vesicles. To maximize volumetric field-of-view at high frequency (15 MHz), NSSM was implemented on row-column arrays that provide the necessary degrees of freedom to operate this imaging mode.

    Using NSSM, we successfully detected bacterial and mammalian cells expressing GVs in a cubic centimeter volume. By visualizing GV expression in cancer cells, NSSM enabled longitudinal tracking of tumor progression and the quantification of necrotic core volumes. Lipid-shelled microbubbles are also agents observable with amplitude modulation sequences. We showed that NSSM at kilohertz framerate enables selective-plane, nonlinear ultrafast
    Doppler imaging of rodent brains perfused with microbubbles. Lastly, we report ultrasound imaging of cerebral capillaries using nonlinear sound sheet localization microscopy, a super-resolution method sensitive to slowest cerebral blood flows. The combination of synthetic and molecular ultrasound contrast agents with fast, high-resolution and volumetric imaging methods carries a wave of opportunities for the field of (bio)molecular ultrasound.
     

  • Advanced ultrasound flow imaging methods such as speckle tracking and vector flow have been of interest for human intraventricular flow imaging in the left ventricle because of the potential to capture subtle deviations from normal heart function. However, reducing the complicated flow patterns into more basic quantities that describe disease progression or normal/abnormal behavior continues to be a major research topic in the quest to translate flow pattern imaging into clinical practice. As is often the case, murine models make excellent candidates to study cardiovascular disease and ultrasound methods are a common tool to quantify cardiac functional parameters. Translating methods proven effective in humans to mice is challenging because of the smaller scale of the mouse heart and a heart rate that is ~10x faster than humans. We have developed a pipeline for multi-angle, plane-wave vector-flow imaging in the murine left ventricle. We initially validated the approach using a Verasonics Vantage with a 15-MHz linear array in a knockout mouse model with a temperature sensitive arrythmia and demonstrated we could quantify changes in vorticity. We are presently undertaking studies with a mouse model of hypertrophy using a 30-MHz linear array and a Verasonics NXT. The increased transmit frequency results in significant aliasing artifacts which we addressed be implementing a double transmit scheme combined with a staggered pulse repetition frequency. Our approach extends the unambiguous velocity range by ~6x verses conventional multi-angle vector flow and permits robust vector-flow estimates.  After establishing repeatability of the method over a range of mouse ages, we performed a longitudinal study as hypertrophy developed to quantify the changes in quantities such as vorticity and energy loss. While the methods we are developing have the potential to inform quantification of flow in the human heart, our focus is on advancing the state of the art for murine cardiac functional imaging.


     

  • The speed of sound of tissue plays a fundamental role in the formation of ultrasound images. Typically, the speed of sound in tissue is assumed to be a constant 1540 m/s, which is the average speed of sound of soft tissue in the human body. The assumption of a constant speed of sound is advantageous because it simplifies the computation of the image reconstruction process. However, the true speed at which the acoustic waves propagate varies with the local tissue, and differences between the assumed and true speed of sound cause distortion of the acoustic wave, familiarly known as aberration. Aberration leads to degraded and suboptimal image quality, reduced resolution, increased image noise, and loss of diagnostic confidence.

    In this talk, we explore a range of sound speed estimation techniques for distributed aberration correction in pulse-echo ultrasound. Estimation of the speed of sound becomes a challenging problem, because the assumption of a heterogeneous speed of sound for a medium leads to unknown positions of the echoes. We begin with simple inversion models relating the propagation average speed of sound to the localized speed of sound and work our way up to more complicated time-of-flight tomography models. These estimates are then used to achieve distributed aberration correction through sound-speed-adapting beamformers, or beamformers that can accommodate heterogeneous sound speed and corrects the entire ultrasound image based on the pixel-by-pixel estimated speed of sound.

    We demonstrate distributed aberration correction techniques, including straight-ray beamforming, eikonal beamforming, and wavefield correlation, including these methods incorporated into differentiable beamforming. The results of these techniques are shown in a variety of phantoms and in vivo examples. Using early inversion sound speed models, distributed aberration correction was successful in simple layered geometries, but lacked
    improvement over more complex distributions of sound speed. Building upon these earlier methods, we developed distributed aberration correction with differentiable beamforming, which iterates between sound speed estimation and image focusing and converges into a well-focused image under heterogenous sound speed conditions. We demonstrate the power of this iterative method from in vivo images in the liver, showing dramatic changes in image quality and potentially establishing new directions for distributed aberration correction.

  • What is the first thing that comes to your mind when you think of ultrasound imaging?  Most of our research participants mentioned ultrasound during pregnancy. As they remember, ultrasound has been a familiar imaging modality for women’s health for a long time. However, the use of contrast-enhanced ultrasound (CEUS), an emerging ultrasound technique, is yet very limited. In this talk, four CEUS applications for women’s health will be introduced: two for breast and others for uterine cervix and placenta. Characterizing breast tumors has been a long-term research problem and CEUS may add diagnostic value. Not all breast cancer patients achieve favorable response from neoadjuvant chemotherapy (NAC) and early assessment of NAC response may improve patients’ survival by allowing earlier therapy modification minimizing unnecessary toxicity. CEUS has been shown potential to predict NAC response early. Cervical insufficiency (CI) describes the inability of the uterine cervix to retain a pregnancy in the absence of the signs and symptoms of clinical contractions, or labor, or both in the second trimester. Unfortunately, there is no objective test to evaluate cervical tissue strength to confirm a diagnosis of CI. Moreover, the diagnosis of CI cannot be made outside of pregnancy by any test. CEUS may help to assess cervix weakness by quantifying its perfusion and pressure in a non-pregnant state. Finally, CEUS may be used to monitor the development of placenta development by assessing placental hemodynamics. During gestation, the uterine vasculature undergoes numerous physiological modifications to produce the necessary increase in blood flow required to support the placental development. The preliminary evaluation results of CEUS bioeffects on the placenta will also be presented.  

  • On-axis elasticity imaging methods are valued for their ability to assess tissue properties directly at the site of mechanical excitation, offering important advantages such as minimal spatial averaging for detailed tissue heterogeneity delineation and low displacement requirements for extended penetration or low output power demands. However, despite these strengths, conventional on-axis methods have been limited by their inability to provide quantitative modulus estimation, restricting their use to semi-quantitative analyses.  To address this limitation, Double Profile Intersection (DoPIo) ultrasound has been developed. DoPIo enables quantitative on-axis modulus estimation by utilizing two simultaneous, confocal beams of different widths to track ARF-induced displacements at the excitation site. The resulting paired displacement profiles capture scatterer shearing rates, which are mapped to elastic moduli through empirically derived and machine learned models. This presentation will highlight the development of and recent advancements to DoPIo, including the method’s extension to assessing mechanical anisotropy. In addition, the technology’s relevance to differentiating healthy, inflamed, and fibrotic kidney tissue, as well as characterizing skeletal muscle, will be demonstrated through ex vivo and in vivo studies in pigs and humans. Finally, ongoing challenges and future directions for further advancing DoPIo technology will be discussed, highlighting its potential to expand the capabilities and applications of ultrasound elasticity imaging.

  • At PRAESENS, we are developing a portable ultrasound solution enhanced with AI, designed to serve the 4.7 billion people worldwide who currently lack access to diagnostic imaging. Born from field-driven insights and real-world constraints, our vision is rooted in practical experience across underserved settings. PRAESENS was originally established as a private foundation by Dr. Rudi Pauwels to strengthen frontline healthcare delivery through innovation. Building on this legacy, we are now working in close industrial partnership with one of the world’s leading medical imaging companies, who recognized the power of our approach in low-resource environments. Our mission is to democratize access to ultrasound by combining affordability, usability, and diagnostic performance—bringing lifesaving imaging capabilities to where they are needed most. 

  • The fast developments in AI, SAW/BAW filters, electronics and chips – both electronic and photonic – open up new frontiers for metrology. Chip structures are becoming more complex, 3D and include new materials. Heterogeneous integration is increasingly used to create aggregate chips. The more complex fabrication requires metrology with increased penetration depths at resolutions beyond those possible with traditional scanning acoustic microscopy (SAM). The solution requires innovative new metrology and transducer concepts.

    AI-based algorithms revolutionize the automated interpretation of ultrasound data – essential for echography to move outside of the domain of expert sonographers (i.e. the hospital). The latter development could help serve an aging population, limit rising health care costs and create new market opportunities. But the sonographer is also key for the correct aiming of the transducer. The automatic recording of the right data requires a large field-of-view and thus often a very large transducer aperture. To maintain good acoustic contact the transducer should be flexible. Outside the hospital space, the transducer should be cheap and come in a practical form factor – e.g. a patch. The solution requires new transducer and fabrication concepts. 

    Historically, in echography the key improvement driver was the hypothesis that higher image quality leads to better diagnoses and increased patient health. Here, a major parameter is the signal-to-noise-ratio (SNR). Diffraction and attenuation reduce pressure levels during propagation. Thus, an SNR increase yields detection at larger depths benefitting traditionally difficult to image patients (e.g. large/obese patients). Peak pressures are limited by safety standards. Thus, more sensitive transducers are required to increase SNR. However, despite continuous research in piezomaterials and electronics improvements in the Noise Equivalent Pressure (NEP) of electromechanical transducers has been limited. A way out could be a new transducer concept based on the interaction of light and sound. 

    Here we present an overview of three new transducer concepts researched at TNO. The first concept is Half-Wavelength Contact Acoustic Microscopy (HaWaCAMTM) aimed at chip inspection. It uses solid-solid contact to side step the SNR and frequency limitations hampering traditional SAM concepts. The second concept is the PillarWaveTM flexible large-area ultrasound transducer fabrication process. It uses micro-structured PVDF-TrFE pillars and side steps some of the challenges of traditional transducer fabrication. The third concept is the Integrated Photonic Ultrasound Transducer (IPUTTM). Literature reports similar devices with a NEP equal to the state-of-the-art but at >100x smaller footprints. Here, we cascade IPUTs to improve the NEP and side step limitations of conventional electromechanical transducers.



     

  • Background, Motivation and Objective
    There is a pressing need for sensors and associated monitoring systems that can operate in industrial high-temperature (HT) harsh environments (HE) well above the 150 °C limit of traditional silicon (Si) microelectronics. Sensor applications in industries such as power generation, aerospace, oil and gas exploration, and high-temperature nuclear microreactors call for robust sensor units and systems that can provide long-term operation with little or no maintenance under high temperatures, vibration, oxidizing environments, temperature cycling, abrupt temperature shocks, and high irradiation conditions. Microwave acoustic materials and devices have been shown to withstand such conditions with minimal to no degradation in performance, while also offering the capability of wireless operation. In addition, wide bandgap semiconductors, such as silicon carbide (SiC) and gallium nitride (GaN), provide possibilities for sensor circuits that can function at high temperatures.

    Statement of Contribution/Methods
    This invited talk and paper discuss recent advances regarding microwave acoustic sensor systems capable of delivering temperature and strain monitoring in HT HE conditions, as well as neutron flux monitoring under intense irradiation and at high temperatures. In addition, HT HE SiC and GaN-based oscillators, along with thermoelectric generators (TEGs) for powering these systems, and integration with acoustic wave sensors are presented.

  • Ultrasonic testing is commonly employed to assess the mechanical properties and structural characteristics of target materials, as the interaction between ultrasonic waves and matter is fundamentally governed by mechanical principles. Furthermore, the spatial resolution of such techniques is inherently constrained by the wavelength of the ultrasonic waves due to Rayleigh diffraction limit. When attempting to measure additional physical properties of the material and achieve a significant enhancement in resolution, conventional ultrasonic methods face substantial limitations.

    The key to achieving this is to find other types waves or particles that can detect such physical properties and modulate them in time domain as input, such as pulsed electron beams, pulsed force, or pulsed light, etc., which can interact with the material to generate acoustic signals carrying targeted information. By integrating techniques such as focused scanning, lock-in amplification, and microscopic imaging, methodologies like scanning electron-acoustic microscopy (SEAM), scanning probe-acoustic microscopy (SPAM), and scanning near-field optoacoustic microscopy (SNOAM) can be developed. These approaches enable us to surpass the Rayleigh diffraction limit, thereby enabling the characterization of various physical properties at the micro- or nanoscale.


    This talk will introduce the progress of our laboratory's work in this field. Based on SEAM, the interaction between electrons and matter enables high-definition imaging of the subsurface electric and magnetic domains as well as the subsurface microstructure of bone tissue. Based on SPAM, the nanoscale force interaction between probes and material surfaces/subsurfaces enables mapping the hydrophilicity of the material, and the residual stress, as well as the microstructure of nucleoskeleton. Based on SNOAM, in addition to investigating molecular light absorption characteristics, it is possible to explore the non-radiative recombination processes of electron-hole pairs in semiconductor materials at nanoscale.
     

  • Acoustic tweezers are a promising technique for the contactless manipulation of objects both in vitro and in vivo, as they are biocompatible, label-free, and capable of remotely handling objects ranging in size from millimeters down to micrometers [1]. Recently, holographic techniques [2] have emerged as powerful tools for shaping acoustic fields, enabling the generation of complex wavefronts to perform advanced tasks such as three-dimensional particle
    manipulation [3,4] and two- or three-dimensional patterning [2,5]. These approaches generally rely on either passive devices that modulate the phase of an input signal generated by a piezoelectric source [2], or on active transducer arrays driven by dedicated electronics that independently control each element's phase and/or amplitude [3,4]. However, in both cases, the achievable resolution is often limited by the inherent constraints in frequency, which restricts their capability to manipulate individual microscopic entities—such as cells or microorganisms—or to achieve micrometer-scale patterning precision.

     

  • This talk presents recent advances of laterally excited shear mode bulk acoustic wave resonators (XBARs). Since Dr. Plessky and colleagues published the first XBAR in 2019, a lot of attention has been paid to XBARs because of their unique features, such as high frequency and large electromechanical coupling factor, which are considered to be difficult to achieve with conventional SAWs and BAWs. Although the XBAR characteristics have been reported by means of simulations and demonstration using simplified resonators and filters, there have been some issues pointed out, such as the intrinsically its fragile-looking suspended structure, manufacturability, reliability for mechanical and power durability, which have not been reported on the feasibility of XBARs as a practical use level in mass production. Characteristics, manufacturability, and reliability of XBAR technologies applied to filters for Wi-Fi applications are presented.

  • The global expansion of 5G and demand for higher mobile speed has created significant new RF filtering challenges. These include higher frequencies, higher bandwidth, more complex filtering requirements such as multiplexers and antennaplexers, lower insertion loss, etc. Many of these challenges demands extremely high precision of film thickness and frequency control in high-volume manufacturing. At higher frequency, the film thickness becomes thinner, thus leading to higher sensitivity for frequency variation.

    Gas Cluster Beam (GCB) technology has been used in trimming of RF filters. There are some unique features with GCB, including, physically driven chemical reaction, high etch rate, low energy per molecule, low power without the need of wafer cooling. This leads to a lower mass of the wafer scanner, which makes its maneuver easier. With a high acceleration voltage of up to 60kV, the potential wafer charge of dozens of volts will have no impact of the etch rate. However, if the acceleration voltage is up to 1000V, the fluctuation of wafer charge voltage will lead to fluctuation of etch rate. Low thermal energy also means that GCB process will not lead to photoresist hardening, thus rendering no issue in photoresist removal. 

    In some trimming applications, zero trimming amount is locally required. We have developed a unique way to control beam power down to zero. This also gives us a control knob to dynamically adjust beam power so that we can handle higher gradient which cannot by handled with mechanical way. Zero Trim capability also allows faster wafer turnaround without the need of larger scanning area, thus improving throughput.

    To have a beam to handle large gradients in the input maps, the GCB beam is focused down to 3.5mm in FWHM (Full Width Half Max). The smaller the beam, the larger the resolution is. The critical parameters to the trimming performance are beam size, beam shape, and alignment. We have developed novel ways to align beam and characterize the beam profile. Beam tuning can be done with this new metrics and gives better trimming performance.

    Many hardware and software improvements have been implemented in the UltraTrimmer tool platform to overcome the challenges in HVM. GCB technology has been widely used in SAW, BAW, FBAR and Thin-Film SAW production. It is currently expanding the application field to MEMS, EUV mask blanks and AR lens production.

  • The state-of-the-art control/tuning/measurement of Li nonstoichiometry in deposited LiNbO3 (LN) films were addressed for the first time and the stoichiometry homogeneity of <0.05 mol% /reproducibility of high-quality LN films at 4’' wafer scale (never demonstrated before) was attained by direct liquid injection (DLI) CVD. CVD growth also assured highly homogeneous thickness on the wafer scale. The epitaxial growth of LN films with unique orientations in the substrate plane (necessary for guided wave applications) in the case of X, Y, and Z orientations (according to IEEE convention) was optimized. In addition, we have succeeded in epitaxially growing new Y128° and Y52° orientations of LN with a single orientation in the plane of the substrate, this is the most used crystal orientation for RF SAW filters. In the literature, only the epitaxy/texture of the Z orientation, (not having good piezoelectric properties) on bottom electrodes has been successful. We have obtained the epitaxial/textured growth of Y33°-LN (the orientation offering optimized electromechanical coupling for thickness mode of bulk acoustic waves) on Pt electrodes. LN film orientation is defined only by the LaNiO3 seed layer and any substrate/structure and electrode, able to withstand LN deposition conditions, can be used. However, the Si substrate was replaced by sapphire or LN substrate in these HBAR and SMR devices in order to reduce thermal stresses and to eliminate chemical interactions of LN with Pt adhesion layers (Ta, Ti, TiO2) and SiO2/Si. Further effort was done to stabilize the heterostructures based on grown LN layers, electrodes and Si substrates by introducing new adhesion layers for Pt electrode and by stress engineering. In order to bring deposited epitaxial (singel crystalline) LN films towards the acoustic devices requiring single crystalline LN films on standard platforms, the layer transfer process is under development. This includes epitaxial growth of LN films on LN substrates with sacrificial layer then bonding on freely chosen structure and liberation of LN film from the growth template by chemical etching.

  • Histotripsy is a non-invasive, non-ionizing, and mechanical ultrasound ablation technique that was invented by Dr. Xu and her colleagues at the University of Michigan. Using microsecond-length, high-pressure ultrasound pulses applied from outside the body and focused to the target diseased tissue, histotripsy produces a cluster of energetic cavitation microbubbles in the target tissue using the endogenous nanometer gas pockets. The rapid expansion and collapse of the cavitation microbubbles produce high local mechanical strain and stress to disrupt the target tissue into liquid-appearing acellular debris with millimeter accuracy. Pre-clinical studies have shown that ultrasound image-guided histotripsy can noninvasively and mechanically disrupt the target tumor while preserving the large normal vessels and other critical structures (e.g., bile ducts). Histotripsy tumor ablation results in tumor reduction or complete eradication, increased survival benefit, and reduced metastasis (abscopal effect). Histotripsy also induces significant innate and adaptive immune response and abscopal effect in murine tumor models. Dr. Xu’s work has led to the FDA approval of non-invasive histotripsy treatment of liver tumors using the EdisonTM system ultrasound image-guided robotic assisted histotripsy platform (HistoSonics) in October 2023. There are ongoing multi-center clinical trials in the U.S. and Europe on histotripsy treatment of renal tumors and pancreatic tumors using the EdisonTM platform. As histotripsy uses ultrasound parameters entirely different from HIFU thermal ablation, Dr. Xu’s group has developed specialized ultrasound transducers and electronic drivers for histotripsy. She will talk about the instrumentation develop of histotripsy, the latest pre-clinical and clinical progress on histotripsy cancer treatment, and her journal to bring this technology from bench to bedside.  

  • The performance of piezoelectric ultrasound transducers is inherently constrained by tradeoffs between sensitivity, size, and bandwidth, limiting their versatility in advanced imaging applications. The Silicon-Photonics Acoustic Detector (SPADE) offers a novel approach that alleviates these limitations by enabling miniaturized, ultra-wideband ultrasound reception. When combined with optoacoustic ultrasound generation, SPADE unlocks new imaging capabilities, facilitating novel configurations for high-resolution optoacoustic tomography and ultrasound. This presentation will delve into the fundamental principles of SPADE technology and showcase its potential imaging applications.

  • High imaging resolution can be achieved through high-frequency ultrasound, which operates at center frequencies of 7-15 MHz. This range has been extensively adopted in clinical applications and plays a critical role in diagnosing thyroid, breast, and musculoskeletal diseases. Furthermore, ultra-high frequency ultrasound, ranging from 15-50 MHz or even higher, is increasingly being integrated into clinical practice. It offers high-resolution imaging with resolutions of less than 100 microns, making it particularly valuable for examining the skin, eyes, blood vessels, and other structures, thereby demonstrating significant potential for broader applications. This talk will focus on the research advancements in high-frequency ultrasound imaging transducers, imaging methodologies, and imaging systems.

    Several innovative high-frequency transducers and systems have been developed to address new imaging challenges and scenarios. We proposed a transparent ultrasonic transducer design using our developed transparent Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (PIN-PMN-PT) crystals. Our fabrication technique incorporates quartz-glass-andepoxy matching layers with low-resistance indium-tin-oxide electrodes through a brass-ring based structure, enabling a high frequency (28.5 MHz), wide bandwidth (78%), and enhanced pulse-echo sensitivity (2.5 V under 2-μJ pulse excitation). In addition, we developed a high-performance focused IVUS transducer using Pb(In1/2Nb1/2)O3-Pb(Sc1/2Nb1/2)O3-PbTiO3 (PIN-PSN-PT) textured ceramics with both high electromechanical performance and high Curie temperature.

    Our transparent ultrasonic transducer demonstrates a four-fold enhancement in photoacoustic detection sensitivity when compared to the LiNbO3-based counterpart, leading to a 13 dB improvement of signal-to-noise ratio in microvascular photoacoustic imaging. This enables dynamic monitoring of mouse cerebral cortex microvasculature during seizures at 0.8 Hz frame rates over a 1.5 × 1.5 mm2 field-of-view. The developed focused IVUS transducer operates at 42 MHz with an -6 dB bandwidth of 72%, featuring a 0.6x0.6 mm2 aperture while maintaining an electrical impedance of approximately 40–60ohm. The axial and lateral resolutions characterized by wire phantom imaging are 45 and 208 um, respectively. The acoustic pressure generated by the focused IVUS transducer is 1.4 times higher than that of its planar counterpart. It is anticipated that these cutting-edge high-frequency ultrasound imaging technologies will soon become standard features in ultrasound equipment, contributing significantly to the advancement of precision medical diagnostics.

  • Neurosurgeons faced with a brain tumor in the operating room have one clear goal: removing as much of the tumor as possible, without damaging functional brain regions. Ultrafast ultrasound imaging - a new high-resolution, mobile neuroimaging technique - has the potential to revolutionize the way we treat brain tumors by visualizing tumor and healthy brain microvasculature as well as functional brain areas in real-time.

    This talk will provide an overview of our team’s combined efforts in the last years to translate ultrafast ultrasound from bench to bedside. We will first discuss results from intra-operative in-human measurements during awake brain surgeries for a range of tumor types. I will highlight how our intra-operative results remain convincing when validated against gold standard techniques such as fMRI and Electro-cortical Stimulation Mapping (ESM). The clinician and patient’s challenge does not end with the surgical procedure alone. Ultrafast Ultrasound has the potential to also change the post-surgical follow-up period, when patients question whether the tumor is growing back or whether chemoradiation treatment is successful. Using clinically approved plastic cranioplasties post-surgery, we demonstrate our ability to monitor tumor regrowth and brain functionality outside of the operating consistently over a period of nearly 2 years. This work demonstrates the potential of ultrafast ultrasound to change the way we treat brain tumors, both in- and outside the operating room, ultimately improving patients’ outcomes.

  • Diagnostics in vascular surgery still rely heavily on anatomical imaging techniques such as contrast-enhanced computed tomography (CT) and magnetic resonance (MR) imaging. However, these methods provide limited information on hemodynamics, which play a crucial role in the onset and progression of atherosclerotic disease. Currently, flow imaging is restricted to duplex ultrasound, which offers only one-dimensional flow estimates at the center of the vessel and is highly operator-dependent. This highlights the need for advanced flow imaging techniques that can provide more comprehensive and reliable hemodynamic assessments.

    While computational fluid dynamics (CFD) and phase-contrast MR imaging (PC-MRI) have demonstrated potential in flow visualization, their clinical adoption remains limited due to high computational demands, long acquisition times, and cost considerations. Ultrasound, in contrast, is widely used in clinical practice due to its accessibility, cost-effectiveness, and real-time imaging capabilities. However, conventional ultrasound techniques are not well suited for detailed flow pattern visualization.

    Recent advancements in plane wave ultrasound imaging offer a promising solution. By significantly increasing the frame rate, these techniques enable flow imaging through particle imaging velocimetry (PIV) algorithms, allowing for the assessment of complex flow patterns in real-time. Initial clinical studies have demonstrated the feasibility of this approach, showing good agreement with PC-MRI, both without contrast agents in superficial arteries and with contrast enhancement in deeper vessels.

    Despite these promising developments, several challenges remain before widespread clinical implementation can be achieved. Future research should focus on identifying clinically relevant flow parameters that correlate with disease progression and outcomes. Additionally, efforts should be made to integrate these techniques into commercially available ultrasound systems, ensuring ease of use and accessibility in routine clinical practice. Overcoming these barriers could pave the way for a new era of hemodynamic assessment in vascular surgery, ultimately improving patient diagnosis and treatment planning.


     

  • Technological progress in diagnostic imaging has been astounding, since the first experiments with cardiac ultrasound by the physicist Hellmuth Hertz and the physician Inge Edler in Lund in 1953. They met through connections when Edler wanted advice about possible imaging of the heart valves, because his patients were dying from early attempts at cardiac surgery. They were
    fortunate in the availability of ultrasonic devices for detecting flaws in metal, and in personal connections with the company that manufactured the equipment, but progress was slow. Hertz
    commented in 1973 that different physicians had very different opinions on the relative importance of possible additional features and no clear answer could be given to the designing
    engineers in industry. It was Christophorus Buijs Ballot from Utrecht – not Christian Doppler – who demonstrated the change in pitch of sound waves from a moving target, in experiments reported in 1845. He was trying to disprove the theory that Doppler had published two years earlier, itself an extension of work by James Bradley in 1727, concerning the red shift of light from distant stars. ‘Doppler’ echocardiography can be traced to Shigeo Satomura in Japan in the early 1950s, but he was aiming to analyse motion of the heart walls. Directional flowmeters were made in the 1960s, and it was not until the 1970s that range-gated Doppler was developed in Norway in order to obtain physiological data for the validation of a computer model of the circulation. Estimation of pressure gradients was proposed in 1976 by Jarle Holen, who had worked as an engineer on Boeing’s supersonic aircraft project before qualifying in medicine – but it was the cardiologist Liv Hatle in Trondheim who had the vision and application really to exploit the new tool for clinical haemodynamic assessment. Doppler myocardial imaging resulted from another joint initiative of physicists and clinicians, in Edinburgh. Progress has been enabled by advances in engineering, but projects that are led by technological breakthroughs risk becoming tools without clinical impact – especially in the era of sophisticated image-processing software with integrated artificial intelligence and machine learning algorithms. For effective innovation, funding must be available for open collaborations between engineers and clinicians, with subsequent engagement by industry. Planning for regulatory approval means demonstrating clinical value.