CIUS: Centre for Innovative Ultrasound Solutions

• Diez, Anja; Viggen, Erlend Magnus & Johansen, Tonni Franke (2024). Open Database of Simulated Ultrasonic Pulse-Echo Well Integrity Log Data. SPE Norway Subsurface Conference. doi: 10.2118/218457-MS. Show summary

  Pulse echo measurements are used to investigate the conditions on the outside of an oil or gas pipe by sendingultrasound pulses onto the pipe wall from inside the pipe that reverberate within the pipe wall. A range ofdifferent algorithms are used today to analyse this data and derive pipe-wall thickness and impedance ofthe material behind the pipe, with the aim of determining the bonding of the material. To be able to developcurrent algorithms further it is crucial to understand currently used algorithms and their advantages anddisadvantages. The downside with using logging data from real boreholes is that no ground truth exists,making it difficult to evaluate the accuracy of the different algorithms. Therefore, we built a databaseof numerically generated data. This database allows us to investigate the effects of variations like casingdiameter, thickness, bonding, and eccentering on the derived casing thickness and outer- material impedanceusing different analysis algorithms. Here, we use three of the most used algorithms and discuss comparisonsof results gained from the analysis of the simulated data in the case of tool eccentering and existence ofa fluid-filled annulus gap between pipe and cement on the outside showing the value of simulated data toimprove and understand estimates of pipe thickness and outer-material impedance.

• Viggen, Erlend Magnus; Diez, Anja & Johansen, Tonni Franke (2024). Pyintegrity: An Open-Source Toolbox for Processing Ultrasonic Pulse-EchoWell Integrity Log Data. SPE Norway Subsurface Conference. doi: 10.2118/218476-MS. Show summary

  Many companies offer similarly designed wireline tools using ultrasonic pulse-echo measurements toevaluate barrier integrity in cased-hole wells. While these tools provide very similar data, differentcompanies process their data using different algorithms, typically to estimate the pipe wall thickness andthe outer material's acoustic impedance. While the algorithms themselves are public, no openly availablesoftware implementations are available. Therefore, we have developed an open-source software toolboxcalled Pyintegrity implementing many of these algorithms. In this article, we demonstrate Pyintegrity byapplying its algorithm implementations to a well integrity log from the open Volve Data Village dataset. Ourresults demonstrate that it is quite possible to process data recorded by a particular tool using processingalgorithms developed for use with other similar tools, and we find a good correspondence between thedifferent processing algorithms. Comparing the results produced by the different processing algorithms letsus confidently identify certain features in some of the results as processing artifacts that do not reflect thephysical state of the well.

• Wifstad, Sigurd Vangen; Kildahl, Henrik Agerup; Grenne, Bjørnar Leangen; Holte, Espen; Hauge, Ståle Wågen & Sæbø, Sigbjørn [Show all 12 contributors for this article] (2024). Mitral Valve Segmentation and Tracking from Transthoracic Echocardiography using Deep Learning. Ultrasound in Medicine and Biology. ISSN 0301-5629. Show summary

  Objective Valvular heart diseases (VHD) pose a significant public health burden, and deciding the best treatment strategy necessitates accurate assessment of heart valve function. Transthoracic Echocardiography (TTE) is the key modality to evaluate VHD, but the lack of standardized quantitative measurements leads to subjective and time-consuming assessments. We aimed to use deep learning to automate the extraction of mitral valve (MV) leaflets and annular hinge points from echocardiograms of the MV, improving standardization and reducing workload in quantitative assessment of MV disease. Methods We annotated the MV leaflets and annulus points in 2931 images from 127 patients. We propose an approach for segmenting the annotated features using Attention UNet with deep supervision and weight scheduling of the attention coefficients to enforce saliency surrounding the MV. The derived segmentation masks were used to extract quantitative biomarkers for specific MV leaflet scallops throughout the heart cycle. Results Evaluation performance was summarized using dice: 0.63 +- 0.14, annulus error: 3.64 +- 2.53, and leaflet angle error: 8.7 +- 8.3 degrees. Leveraging Attention UNet with deep supervision robustness of clinically relevant metrics was improved compared to UNet, reducing standard deviation by: 2.7 degrees (angle error), 0.73 mm (annulus error). We correctly identified cases of MV prolapse, cases of stenosis, and healthy references from a clinical material using the derived biomarkers. Conclusion Robust deep learning segmentation and tracking of MV morphology and motion is possible by leveraging attention gates and deep supervision, and holds promise for enhancing VHD diagnosis and treatment monitoring.

• Liu, Xueqing; Ytterdal, Trond & Shur, Michael S. (2024). Compact Spice Models for Terafets. International Journal of High Speed Electronics and Systems. ISSN 0129-1564. doi: 10.1142/S0129156424500046.
• Szerypo Magelssen, Malgorzata Izabela; Hjorth-Hansen, Anna; Andersen, Garrett Newton; Graven, Torbjørn; Kleinau, Jens Olaf & Skjetne, Kyrre [Show all 9 contributors for this article] (2023). Clinical Influence of Handheld Ultrasound, Supported by Automatic Quantification and Telemedicine, in Suspected Heart Failure. Ultrasound in Medicine and Biology. ISSN 0301-5629. 49(5), p. 1137–1144. doi: 10.1016/j.ultrasmedbio.2022.12.015.
• Diez, Anja; Johansen, Tonni Franke & Viggen, Erlend Magnus (2023). From 3D to 1D: Effective numerical modelling of pulse-echo measurements in pipes. In Viggen, Erlend Magnus (Eds.), Proceedings of the 46th Scandinavian Symposium on Physical Acoustics. Norsk Fysisk Selskap. ISSN 978-82-8123-023-1. Show summary

  In the oil and gas industry, pulse echo measurements have for decades been used in cased holes to estimate the properties of the materials on the outside of the pipe. To investigate the methods used to analyse pulse echo measurements from pipes, we use numerical modelling in COMSOL Multiphysics. While 3D models correctly capture the real geometry, they are computationally heavy and, therefore, not appropriate for simulating a large range of geometric and material variations. Analytic 1D plane wave models are fast to calculate, but we observe large deviations between the 3D and 1D results, showing that corrections to 1D model results are necessary. Therefore, we investigate using 2D and axisymmetric 2.5D models instead and find good agreement between the 2.5D and 3D model results and larger deviations between the 2D and 3D model results. Further, we find that the time explicit formulation works reliably, with an effective absorbing layer, while using the time domain formulation requires more care and a larger domain due to the poorer performance of its perfectly matched layer. Nevertheless, the time domain formulation is preferable when introducing thin domains and additional domain boundaries to keep the computational time at an acceptable level.

• Shur, M.S.; Liu, X. & Ytterdal, Trond (2023). Editors’ Choice—Thin Film Transistor Response in the THz Range. ECS Journal of Solid State Science and Technology. ISSN 2162-8769. 12(3). doi: 10.1149/2162-8777/acc20d.
• Salte, Ivar Mjåland; Østvik, Andreas; Olaisen, Sindre Hellum; Karlsen, Sigve; Dahlslett, Thomas & Smistad, Erik [Show all 13 contributors for this article] (2023). Deep Learning for Improved Precision and Reproducibility of Left Ventricular Strain in Echocardiography: A Test-Retest Study. Journal of the American Society of Echocardiography. ISSN 0894-7317. 36(7), p. 788–799. doi: 10.1016/j.echo.2023.02.017. Full text in Research Archive
• Letnes, Jon Magne; Nes, Bjarne Martens; Langlo, Knut Asbjørn Rise; Aksetøy, Inger-Lise Aamot; Lundgren, Kari Margrethe & Skovereng, Knut [Show all 9 contributors for this article] (2023). Indexing cardiac volumes for peak oxygen uptake to improve differentiation of physiological and pathological remodeling: from elite athletes to heart failure patients. European Heart Journal-Cardiovascular Imaging. ISSN 2047-2404. 24(6), p. 721–729. doi: 10.1093/ehjci/jead034. Full text in Research Archive
• Viggen, Erlend Magnus & Arnestad, Håvard (2023). Modelling acoustic radiation from vibrating surfaces around coincidence: Radiation into fluids. Journal of Sound and Vibration. ISSN 0022-460X. 560. doi: 10.1016/j.jsv.2023.117787. Full text in Research Archive Show summary

  It is well-known that vibrating surfaces generate sound waves in adjacent fluids. According to the classical radiation model, the nature of these waves depends on whether the vibration’s phase speed cv is above (supersonic) or below (subsonic) the fluid sound speed cf. The transition between these two domains is known as coincidence. In the supersonic domain, the sound wave radiates into the fluid. In the subsonic domain, the classical model states that the wave becomes evanescent and clings to the surface. In the last 30 years, however, several articles on leaky guided waves have reported radiating waves in the subsonic domain, which is at odds with the classical model. In this article, we investigate an enhanced model for sound radiation near and below coincidence. Unlike the classical model, this model fully respects conservation of energy by balancing the radiated power with power lost from the guided wave underlying the vibration. The model takes into account that this power loss and the consequent attenuation of the surface vibration result in an inhomogeneous radiated sound wave — an effect that cannot be neglected near coincidence. We successfully validate the model against exact solutions for leaky A0 Lamb waves around coincidence. The model can also be used as a perturbation method to predict the attenuation of leaky A0 waves from the properties of free A0 waves, giving more accurate estimates than existing perturbation methods. We further investigate subsonic leaky A0 waves using the enhanced model. Thereby we, for example, explain the peculiar reappearance or persistence of the leaky A0 wave at lower frequencies, an effect brought to attention by previous theoretical studies.

• Johansen, Tonni Franke; Buschmann, Philip Erik; Røsberg, Knut Marius; Diez, Anja & Viggen, Erlend Magnus (2023). Ultrasonic well integrity logging using phased array technology, ASME 2023 42nd International Conference on Ocean, Offshore and Arctic Engineering: Volume 9: Offshore Geotechnics; Petroleum Technology. The American Society of Mechanical Engineers (ASME). ISSN 978-0-7918-8691-5. doi: 10.1115/OMAE2023-108101. Full text in Research Archive Show summary

  Ultrasonic well integrity logging is an important and common procedure for well completion and plug-and-abandonment operations. Typical logging tools employ single-element ultrasound transducers. In medical ultrasound imaging, however, more flexible phased arrays are the standard. This paper presents a first set of experimental results obtained with up to two linear 32-element phased arrays that are specifically designed for plug-and-abandonment operations in terms of their centre frequency. The experiments encompass pulse-echo and pitch-catch studies for different incidence angles and aperture sizes on plates and pipes with wall thickness as encountered in the offshore industry. The pulse-echo experiment is backed up by simulations, and shows that effect of the incidence angle on the pipe resonance’s frequency and strength is weak and more strong, respectively, and that the effect depends on the frequency response and directivity of the transducer. The pitch-catch experiment demonstrates the importance of carefully choosing the right angle of incidence to excite the intended wave modes.

• Støylen, Asbjørn; Hansen, Harald Edvard Mølmen & Dalen, Håvard (2023). Regional motion of the AV-plane is related to the cardiac anatomy and deformation of the AV-plane. Data from the HUNT study. Clinical Physiology and Functional Imaging. ISSN 1475-0961. 43(6), p. 453–462. doi: 10.1111/cpf.12845. Show summary

  The study examines global and regional systolic shortening of the left (LV) and right ventricle (RV) in 1266 individuals without evidence of heart disease in the third wave of the HUNT study. Regional mitral annular systolic displacement (mitral annular plane systolic excursion [MAPSE]) was 1.5 cm in the septum and anterior walls, 1.6 cm in the lateral wall and 1.7 cm in the inferior wall, global mean 1.6 cm. Peak systolic velocity S' was 8.0, 8.3, 8.8 and 8.6 cm/s in the same walls (global mean 8.7 cm/s). All measures of LV longitudinal shortening correlated, mean MAPSE and S' also correlated with stroke volume (SV) and ejection fraction (EF). Global longitudinal strain by either method correlated with MAPSE, S' and EF, but not with SV, reflecting a systematic difference. S' and MAPSE correlated with early annular diastolic velocity (e'), reflecting that e' is the recoil from systole. Mean displacement was 2.8 (0.5) cm in the tricuspid annulus (tricuspid annular plane systolic excursion [TAPSE]). Normal values by age and sex are provided. Both TAPSE and S' were lower in women, where body size explained the sex difference. Normalisation of MAPSE and S' for wall length reduced intra-individual variation of displacement and velocity by 80%–90%, showing regional MAPSE to be related to LV wall length, and that longitudinal wall strain was relatively uniform. Displacement and S' were lowest in the septum and highest in the left and right free walls, shows systolic bending of the AV-plane into a U-shape, relating to the total cardiac volume changes during the heart cycle.

• Holm, Sverre; Chandrasekaran, Sri Nivas & Näsholm, Sven Peter (2023). Adding a low frequency limit to fractional wave propagation models. Frontiers in Physics. ISSN 2296-424X. 11, p. 1–8. doi: 10.3389/fphy.2023.1250742. Full text in Research Archive Show summary

  Power-law attenuation in elastic wave propagation of both compressional and shear waves can be described with multiple relaxation processes. It may be less physical to describe it with fractional calculus medium models, but this approach is useful for simulation and for parameterization where the underlying relaxation structure is very complex. It is easy to enforce a low-frequency limit on a relaxation distribution and this gives frequency squared characteristics for low frequencies which seems to fit some media in practice. Here the goal is to change the low-frequency behavior of fractional models also. This is done by tempering the relaxation moduli of the fractional Kelvin-Voigt and diffusion models with an exponential function and the effect is that the low-frequency attenuation will increase with frequency squared and the square root of frequency respectively. The time-space wave equations for the tempered models have also been found, and for this purpose the concept of the fractional pseudo-differential operator borrowed from the field of Cole-Davidson dielectrics is useful. The tempering does not remove the singularity in the relaxation moduli of the models, but this has only a minor effect on the solutions.

• Tasken, Anders Austlid; Berg, Erik Andreas Rye; Grenne, Bjørnar Leangen; Holte, Espen; Dalen, Håvard & Stølen, Stian Bergseng [Show all 9 contributors for this article] (2023). Automated estimation of mitral annular plane systolic excursion by artificial intelligence from 3D ultrasound recordings. Artificial Intelligence in Medicine. ISSN 0933-3657. 144. doi: 10.1016/j.artmed.2023.102646. Full text in Research Archive Show summary

  Perioperative monitoring of cardiac function is beneficial for early detection of cardiovascular complications. The standard of care for cardiac monitoring performed by trained cardiologists and anesthesiologists involves a manual and qualitative evaluation of ultrasound imaging, which is a time-demanding and resource-intensive process with intraobserver- and interobserver variability. In practice, such measures can only be performed a limited number of times during the intervention. To overcome these difficulties, this study presents a robust method for automatic and quantitative monitoring of cardiac function based on 3D transesophageal echocardiography (TEE) B-mode ultrasound recordings of the left ventricle (LV). Such an assessment obtains consistent measurements and can produce a near real-time evaluation of ultrasound imagery. Hence, the presented method is time-saving and results in increased accessibility. The mitral annular plane systolic excursion (MAPSE), characterizing global LV function, is estimated by landmark detection and cardiac view classification of two-dimensional images extracted along the long-axis of the ultrasound volume. MAPSE estimation directly from 3D TEE recordings is beneficial since it removes the need for manual acquisition of cardiac views, hence decreasing the need for interference by physicians. Two convolutional neural networks (CNNs) were trained and tested on acquired ultrasound data of 107 patients, and MAPSE estimates were compared to clinically obtained references in a blinded study including 31 patients. The proposed method for automatic MAPSE estimation had low bias and low variability in comparison to clinical reference measures. The method accomplished a mean difference for MAPSE estimates of (-0.16 +- 1.06) mm. Thus, the results did not show significant systematic errors. The obtained bias and variance of the method were comparable to inter-observer variability of clinically obtained MAPSE measures on 2D TTE echocardiography. The novel pipeline proposed in this study has the potential to enhance cardiac monitoring in perioperative- and intensive care settings.

• Gopinath, Anoop; Ytterdal, Trond; Lee, John; Rizkalla, Maher & Kumar, Mukesh (2023). SRAM Process and Debug Sensor. In Cerny, Charles (Eds.), Proceedings of the 2023 IEEE National Aerospace and Electronics Conference. IEEE (Institute of Electrical and Electronics Engineers). ISSN 979-8-3503-3878-2. doi: 10.1109/NAECON58068.2023.10365775.
• Kildahl, Henrik Agerup; Brenne, Evelyn Merete Lauvstad; Dalen, Håvard & Wahba, Alexander (2023). Systemic embolization in infective endocarditis. Indian journal of thoracic and cardiovascular surgery. ISSN 0970-9134. doi: 10.1007/s12055-023-01616-2.
• Siu, Hoi Yi; Hoff, Lars & Frijlink, Martijn (2023). High Temperature Performance of 3 MHz 36° Y-Cut Lithium Niobate Ultrasonic Transducer for Non-Destructive Testing at 550 °C. Proceedings - IEEE Ultrasonics Symposium. ISSN 1948-5719. doi: 10.1109/IUS51837.2023.10308184.
• Le, Hoang Duy; Manh, Tung & Hoff, Lars (2023). A novel wide-band design of dual-frequency transducer based on PZT-PVDF for super harmonic imaging. Proceedings - IEEE Ultrasonics Symposium. ISSN 1948-5719. doi: 10.1109/IUS51837.2023.10308044.
• Mansoori, Amirfereydoon; Hoff, Lars; Salmani, Hamed & Halvorsen, Einar (2023). Electrode Design Based on Strain Mode Shapes for Configurable PMUTs. IEEE Open Journal of Ultrasonics, Ferroelectrics, and Frequency Control Society (OJUFFC). ISSN 2694-0884. 3, p. 88–100. doi: 10.1109/OJUFFC.2023.3289169. Full text in Research Archive
• Bolstad, Per Kristian; Frijlink, Martijn & Hoff, Lars (2023). Evaluation of bonding techniques for ultrasound transducers. Microelectronics and reliability. ISSN 0026-2714. 151. doi: 10.1016/j.microrel.2023.115272.
• Sæbø, Sigbjørn; Pettersen, Håkon Neergaard; Smistad, Erik; Pasdeloup, David Francis Pierre; Stølen, Stian Bergseng & Grenne, Bjørnar Leangen [Show all 9 contributors for this article] (2023). Real-time guiding by deep learning during echocardiography to reduce left ventricular foreshortening and measurement variability. European Heart Journal - Imaging Methods and Practice. ISSN 2755-9637. 1. doi: 10.1093/ehjimp/qyad012.
• Hu, Jieyu; Smistad, Erik; Grenne, Bjørnar Leangen; Holte, Espen; Dalen, Håvard & Løvstakken, Lasse (2023). Left-Ventricular Volume Estimation in Contrast-Enhanced Echocardiography Using Deep Learning, Proceedings of the 2023 IEEE International Ultrasonics Symposium (IUS). IEEE conference proceedings. ISSN 979-8-3503-4645-9. doi: 10.1109/IUS51837.2023.10308094. Full text in Research Archive
• Chandrasekaran, Sri Nivas; Holm, Sverre & Näsholm, Sven Peter (2023). Wave equations of the two common sediment acoustic theories. Proceedings of Meetings on Acoustics (POMA). ISSN 1939-800X. 51. doi: 10.1121/2.0001795. Full text in Research Archive Show summary

  Two popular theories for wave propagation in sediments, the Biot poroelastic theory and the Viscous Grain Shearing (VGS) theory, have been formulated in terms of dispersion relations. The lack of explicit wave equations for these models could be considered to be a weakness. Hence, providing wave equations that are fully consistent with these theories might confirm that they have a physical basis. In the Biot theory, it is the frequency-dependent viscodynamic operator that poses the problem as there is no equivalent time-domain operator. Previous work has shown that this factor can be approximated well with a simplified square root operator. Drawing on the parallel to the Cole-Davidson dielectric theory for complex media where the same factor appears, and using the equivalent time-domain operator, which is a fractional pseudo-differential operator, enables the formulation of wave equations for all three wave modes of the Biot theory. The same operator turns out to be central for transforming the dispersion relations of the VGS theory to time-space wave equations. In this case, the relation between the dispersion equations and the wave equations is exact. The wave equations of these two theories will enable a closer study of the properties of the medium models.

• Berg, Erik Andreas Rye; Tasken, Anders Austlid; Nordal, Trym; Grenne, Bjørnar Leangen; Espeland, Torvald & Garstad, Idar Kirkeby [Show all 11 contributors for this article] (2023). Fully automatic estimation of global left ventricular systolic function using deep learning in transesophageal echocardiography. European Heart Journal - Imaging Methods and Practice. ISSN 2755-9637. 1(1). doi: 10.1093/ehjimp/qyad007. Full text in Research Archive Show summary

  Aims To improve monitoring of cardiac function during major surgery and intensive care, we have developed a method for fully automatic estimation of mitral annular plane systolic excursion (auto-MAPSE) using deep learning in transoesophageal echocardiography (TOE). The aim of this study was a clinical validation of auto-MAPSE in patients with heart disease. Methods and results TOE recordings were collected from 185 consecutive patients without selection on image quality. Deep-learning-based auto-MAPSE was trained and optimized from 105 patient recordings. We assessed auto-MAPSE feasibility, and agreement and inter-rater reliability with manual reference in 80 patients with and without electrocardiogram (ECG) tracings. Mean processing time for auto-MAPSE was 0.3 s per cardiac cycle/view. Overall feasibility was >90% for manual MAPSE and ECG-enabled auto-MAPSE and 82% for ECG-disabled auto-MAPSE. Feasibility in at least two walls was ≥95% for all methods. Compared with manual reference, bias [95% limits of agreement (LoA)] was −0.5 [−4.0, 3.1] mm for ECG-enabled auto-MAPSE and −0.2 [−4.2, 3.6] mm for ECG-disabled auto-MAPSE. Intra-class correlation coefficient (ICC) for consistency was 0.90 and 0.88, respectively. Manual inter-observer bias [95% LoA] was −0.9 [−4.7, 3.0] mm, and ICC was 0.86. Conclusion Auto-MAPSE was fast and highly feasible. Inter-rater reliability between auto-MAPSE and manual reference was good. Agreement between auto-MAPSE and manual reference did not differ from manual inter-observer agreement. As the principal advantages of deep-learning-based assessment are speed and reproducibility, auto-MAPSE has the potential to improve real-time monitoring of left ventricular function. This should be investigated in relevant clinical settings.

• Mohajery, Mohammad; Salles, Sebastien Andre Roger; Espeland, Torvald; Fadnes, Solveig & Løvstakken, Lasse (2023). Automated 3D velocity estimation of natural mechanical wave propagation in the myocardium. IEEE Open Journal of Ultrasonics, Ferroelectrics, and Frequency Control Society (OJUFFC). ISSN 2694-0884. 3, p. 210–222. doi: 10.1109/OJUFFC.2023.3344372.
• Hu, Jieyu; Olaisen, Sindre Hellum; Smistad, Erik; Dalen, Håvard & Løvstakken, Lasse (2023). Automated 2-D and 3-D Left Atrial Volume Measurements Using Deep Learning. Ultrasound in Medicine and Biology. ISSN 0301-5629. 50(1), p. 47–56. doi: 10.1016/j.ultrasmedbio.2023.08.024. Full text in Research Archive
• Feyling, Fredrik Esp; Malmberg, Hampus; Wulff, Carsten; Loeliger, Hans-Andrea & Ytterdal, Trond (2023). Design and Analysis of the Leapfrog Control-Bounded A/D Converter. IEEE Transactions on Very Large Scale Integration (vlsi) Systems. ISSN 1063-8210. 32(1), p. 79–88. doi: 10.1109/TVLSI.2023.3320279.
• Shur, Michael S.; Liu, Xueqing & Ytterdal, Trond (2023). Switching Characteristics of GaN Power Transistors. ECS Transactions. ISSN 1938-5862. 112(2), p. 45–55. doi: 10.1149/11202.0045ecst.
• Gopinath, Anoop; Ytterdal, Trond; Yadhav, Avinash; Lee, John; Rizkalla, Maher & Kumar, Mukesh (2023). SRAM Vmin Scaling Via Negative Wordline. In Abshire, Pamela (Eds.), Proceedings of the 66th IEEE International Midwest Symposium on Circuits and Systems. IEEE (Institute of Electrical and Electronics Engineers). ISSN 979-8-3503-0210-3. p. 227–231. doi: 10.1109/MWSCAS57524.2023.10406117.
• Balasubramanian, Linknath Surya; Rizkalla, Maher; Lee, John; Ytterdal, Trond & Kumar, Mukesh (2023). Towards No Penalty Control Hazard Handling. In Abshire, Pamela (Eds.), Proceedings of the 66th IEEE International Midwest Symposium on Circuits and Systems. IEEE (Institute of Electrical and Electronics Engineers). ISSN 979-8-3503-0210-3. p. 1128–1131. doi: %2010.1109/MWSCAS57524.2023.10405871.
• Cochran, Zachary; Rizkalla, Maher; Lee, John; Ytterdal, Trond & Balasubramanian, Linknath Surya (2023). Ultra Low-Power Low-Noise GNRFET Wideband Amplifier for Cryogenic Applications. In Cerny, Charles (Eds.), Proceedings of the 2023 IEEE National Aerospace and Electronics Conference. IEEE (Institute of Electrical and Electronics Engineers). ISSN 979-8-3503-3878-2. doi: 10.1109/NAECON58068.2023.10415305.
• Espeland, Torvald; Wigen, Morten Smedsrud; Dalen, Håvard; Berg, Erik Andreas Rye; Hammer, Tommy Arild & Salles, Sebastien Andre Roger [Show all 9 contributors for this article] (2023). Mechanical Wave Velocities in Left Ventricular Walls in Healthy Subjects and Patients With Aortic Stenosis. JACC Cardiovascular Imaging. ISSN 1936-878X. 17(2), p. 111–124. doi: 10.1016/j.jcmg.2023.07.009. Full text in Research Archive
• Kasongo, Muana; Ytterdal, Trond; Lee, John; Rizkalla, Maher & Kumar, Mukesh (2023). Evaluation of Leakage Currents in Memristor Crossbar Arrays. In Cerny, Charles (Eds.), Proceedings of the 2023 IEEE National Aerospace and Electronics Conference. IEEE (Institute of Electrical and Electronics Engineers). ISSN 979-8-3503-3878-2. doi: 10.1109/NAECON58068.2023.10365978.
• Shur, Michael S.; Liu, Xueqing & Ytterdal, Trond (2023). Phase-sensitive Silicon CMOS TeraFETs. In Cooke, David (Eds.), 2023 48th International Conference on Infrared, Millimeter, and Terahertz Waves. IEEE (Institute of Electrical and Electronics Engineers). ISSN 979-8-3503-3660-3. doi: 10.1109/IRMMW-THz57677.2023.10298984.
• Rindal, Ole Marius Hoel; Bjåstad, Tore Grüner; Espeland, Torvald; Berg, Erik Andreas Rye & Måsøy, Svein-Erik (2023). A Very Large Cardiac Channel Data Database (VLCD) Used to Evaluate Global Image Coherence (GIC) as an In Vivo Image Quality Metric. IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control. ISSN 0885-3010. 70(10), p. 1295–1307. doi: 10.1109/TUFFC.2023.3308034. Full text in Research Archive Show summary

  Ultrasound image quality is of utmost importance for a clinician to reach a correct diagnosis. Conventionally, image quality is evaluated using metrics to determine the contrast and resolution. These metrics requires localization of specific regions and targets in the image such as a region of interest (ROI), a background region, and or, a point scatterer. Such objects can all be difficult to identify in in-vivo images, especially for automatic evaluation of image quality in large amounts of data. Using a matrix array probe, we have recorded a Very Large cardiac Channel data Database (VLCD) to evaluate coherence as an in-vivo image quality metric. The VLCD consists of 33 280 individual image frames from 538 recordings of 106 patients. We also introduce a Global Imag Coherence (GIC), an in-vivo image quality metric that does not require any identified ROI since it is defined as an average coherence value calculated from all the data pixels used to form the image, below a pre-selected range. The GIC is shown to be a quantitative metric for in-vivo image quality when applied to the VLCD. We demonstrate, on a subset of the dataset, that the GIC correlates well with the conventional metrics contrast ratio (CR) and the generalized contrast-to-noise ratio (gCNR)with R=0.74 (p0.9, p

• Ness, Henning Ofstad; Ljones, Kristine; Gjelsvik, Randi Hansgård; Tjønna, Arnt Erik; Malmo, Vegard & Nilsen, Hans-Olav [Show all 9 contributors for this article] (2022). Acute effects of high intensity training on cardiac function: a pilot study comparing subjects with type 2 diabetes to healthy controls. Scientific Reports. ISSN 2045-2322. 12. doi: 10.1038/s41598-022-12375-2. Full text in Research Archive Show summary

  This study evaluated acute cardiac stress after a high-intensity interval training session in patients with type 2 diabetes (T2D) versus healthy controls. High intensity aerobic exercise was performed by 4 × 4-min intervals (90–95% of maximal heart rate), followed by a ramp protocol to peak oxygen uptake. Echocardiography was performed before and 30 min after exercise. Holter electrocardiography monitored heart rhythms 24 h before, during, and 24 h after the exercise. Left atrial end-systolic volume, peak early diastolic mitral annular velocity, and the ratio of peak early to late diastolic mitral inflow velocity were reduced by approximately 18%, 15%, and 31%, respectively, after exercise across groups. Left ventricular end-diastolic wall thickness was the only echo parameter that significantly differed between groups in response to exercise. The T2D group had a rate of supraventricular extrasystoles per hour that was 265% greater than that of the controls before exercise, which remained higher after exercise. A single exhaustive exercise session impaired left ventricular diastolic function in both groups. The findings also indicated impaired right ventricular function in patients with T2D after exercise.

• Ingul, Charlotte Bjørk; Edvardsen, Anne; Follestad, Turid; Trebinjac, Divna; Ankerstjerne, Odd Andre Wathne & Brønstad, Eivind [Show all 14 contributors for this article] (2022). Changes in cardiopulmonary exercise capacity and limitations 3-12 months after COVID-19. European Respiratory Journal. ISSN 0903-1936. 61(2). doi: 10.1183/13993003.00745-2022. Full text in Research Archive
• Hjorth-Hansen, Anna Katarina; Magelssen, Malgorzata Isabela; Andersen, Garrett Newton; Graven, Torbjørn; Kleinau, Jens Olaf & Landstad, Bodil [Show all 10 contributors for this article] (2022). User experience and image quality influence on performance of automated real-time quantification of left ventricular function by handheld ultrasound devices: a diagnostic accuracy study with data from general practitioners, nurses and cardiologists. Open heart. ISSN 2053-3624. 9(2). doi: 10.1136/openhrt-2022-002083. Full text in Research Archive
• Shur, Michael S.; Liu, Xueqing & Ytterdal, Trond (2022). Improved Thin Film Transistor Model Predicts TFT Operation in the THz Range. ECS Transactions. ISSN 1938-5862. 109(6), p. 3–12. doi: 10.1149/10906.0003ecst.
• Liu, Xueqing; Ytterdal, Trond & Shur, Michael S. (2022). Multi-Segment TFT Compact Model for THz Applications. Nanomaterials. ISSN 2079-4991. 12(5). doi: 10.3390/nano12050765. Full text in Research Archive
• Shur, Michael S.; Liu, Xueqing & Ytterdal, Trond (2022). Plasmonic Si CMOS TeraFETs for detection, mixing, and processing sub-THz radiation. Proceedings of SPIE, the International Society for Optical Engineering. ISSN 0277-786X. 12000. doi: 10.1117/12.2615536.
• Yadhav, Avinash; Rizkalla, Maher; Ytterdal, Trond; Lee, John J.; Balasubramanian, Linknath Surya & Gopinath, Anoop (2022). Evaluation of FinFET in Ultra Low Power ALU. In Masmoudi, Mohamed (Eds.), Proceedings of the 4th IEEE International Conference on Design & Test of Integrated Micro & Nano-Systems. IEEE conference proceedings. ISSN 978-1-6654-9784-8. doi: 10.1109/DTS55284.2022.9809864.
• Hjorth-Hansen, Anna; Magelssen, Malgorzata Isabela; Andersen, Garrett Newton; Graven, Torbjørn; Kleinau, Jens Olaf & Landstad, Bodil [Show all 10 contributors for this article] (2022). Real-time automatic quantification of left ventricular function by hand-held ultrasound devices in patients with suspected heart failure: a feasibility study of a diagnostic test with data from general practitioners, nurses and cardiologists. BMJ Open. ISSN 2044-6055. 12(10). doi: 10.1136/bmjopen-2022-063793. Full text in Research Archive

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• Viggen, Erlend Magnus (2024). Proceedings of the 47th Scandinavian Symposium on Physical Acoustics. Norsk Fysisk Selskap. ISBN 978-82-8123-024-8. 18 p.
• Viggen, Erlend Magnus (2023). Proceedings of the 46th Scandinavian Symposium on Physical Acoustics. Norsk Fysisk Selskap. ISBN 978-82-8123-023-1. 87 p.

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• Dalen, Håvard (2024). Hjertefysiologi og rehabilitering.
• Dalen, Håvard (2024). Sharing of sensitive data.
• Dalen, Håvard (2024). Kunstig intelligens ved ekkokardiografi.
• Dalen, Håvard (2024). Forskning som endrer klinisk praksis.
• Rye, Cathrine Sæthern & Dalen, Håvard (2024). Kvalitet på kardiovaskulære diagnoser i sykehus.
• Viggen, Erlend Magnus & Arnestad, Håvard (2023). Why leaky flexural plate waves misbehave at low frequencies.
• Pettersen, Håkon Neergaard; Sæbø, Sigbjørn; Smistad, Erik; Pasdeloup, David Francis Pierre; Stølen, Stian Bergseng & Grenne, Bjørnar Leangen [Show all 9 contributors for this article] (2023). Real-time guiding by deep learning during echocardiography to reduce left ventricular foreshortening and measurement variability.
• Diez, Anja; Johansen, Tonni Franke & Viggen, Erlend Magnus (2023). From 3D to 1D – effective numerical modelling of pulse-echo measurements in pipes.
• Vrålstad, Anders Emil; Kvalevåg, Magnus; Rindal, Ole Marius Hoel & Måsøy, Svein-Erik (2023). Universal REFoCUS with Spatial Weighting. Show summary

  The REFoCUS algorithm decomposes any arbitrary transmit wave into its Huygens-Fresnel components allowing Synthetic Transmit Aperture (STA) beamforming. The STA dataset is found by advancing the backscattered channel data by the applied transmit (Tx) delay and summing across Tx events. This simple advance-and-sum, also called adjoint inversion in frequency domain, has shown image quality similar to true STA beamforming for phased array sequences, but showed artifacts for sequences with walking aperture [1]. The artifacts were suppressed by regularizing the inversion at the cost of SNR [2]. Our time-domain implementation with pixel dependent apodization aims to generalize the REFoCUS method for all scan setups without introducing artifacts. The apodization is based on the directivity limitations of transducer elements, and it also works for 2D arrays using Sub-Aperture (SAP) technology.

• Gopinath, Anoop; Ytterdal, Trond; Lee, John; Rizkalla, Maher & Kumar, Mukesh (2023). SRAM Process and Debug Sensor.
• Pasdeloup, David Francis Pierre; Østvik, Andreas; Olaisen, Sindre Hellum; Skogvoll, Eirik; Dalen, Håvard & Løvstakken, Lasse (2023). Automated measurements with AI: the gap between proof-of-concept and clinical use.
• Hu, Jieyu; Smistad, Erik; Grenne, Bjørnar Leangen; Holte, Espen; Dalen, Håvard & Løvstakken, Lasse (2023). Left-Ventricular Volume Estimation in Contrast-Enhanced Echocardiography Using Deep Learning.
• Normannsen, Sølvi W. & Måsøy, Svein-Erik (2023). Forskere kan takke gamere for bedre ultralydbilder av hjertet. [Business/trade/industry journal]. Gemini.no. Show summary

  Spillindustriens jag etter superraske mikroprosessorer har hjulpet norske forskere til å løse et 40 år gammelt ultralyd-problem.

• Rindal, Ole Marius Hoel; Fiorentini, Stefano; Avdal, Jørgen; Austeng, Andreas & Rodriguez Molares, Alfonso (2023). The Generalized Beamformer in the UltraSound ToolBox. Show summary

  Access to channel data, and real-time processing of such, have left us a landscape filled with beamforming techniques often using specific wavefronts with specific reconstruction algorithms. This implies high costs for code maintenance and makes it difficult to compare different techniques. We demonstrate a generalized beamformer (GB) to reconstruct any transmit (tx) waveform from any probe into a defined grid of pixels. It covers linear and sector scans, both steered and stepped tx and even complex beamforming such as multiple line acquisition (MLA) and retrospective tx beamforming (RTB). Also, we show how the GB can be utilized to improve the channel data used for adaptive beamforming.

• Rindal, Ole Marius Hoel; Vrålstad, Anders Emil; Bjåstad, Tore Grüner; Sørnes, Anders Rasmus & Måsøy, Svein-Erik (2023). Improving Image Quality Degradation due to Blocked Array in Cardiac Ultrasound Imaging. Show summary

  The footprint of a cardiac ultrasound (US) probe is designed to fit the size of the intercostal space between the ribs to avoid ribs blocking the US energy. Some patients will have an intercostal space narrower than the footprint, making array blockage inevitable. In some cases, the clinician may be forced to place the probe in a position subject to rib blockage to achieve the desired anatomical view. Firstly, we demonstrate that such rib blockages reduce the image quality and lead to depth-varying geometrical distortions, potentially tilting structures and reducing resolution. Secondly, we demonstrate that compensating for the blocked array in the retrospective transmit beamforming (RTB) corrects most of the unwanted effects and improves image quality.

• Siu, Hoi Yi; Hoff, Lars & Frijlink, Martijn (2023). High Temperature Performance of 3 MHz 36° Y-Cut Lithium Niobate Ultrasonic Transducer for Non-Destructive Testing at 550 °C.
• Le, Hoang Duy; Manh, Tung & Hoff, Lars (2023). A novel wide-band design of dual-frequency transducer based on PZT-PVDF for super harmonic imaging.
• Olaisen, Sindre Hellum (2023). AI-based measurements in echocardiography, clinical results.
• Måsøy, Svein-Erik; Dénarié, Bastien Emmanuel; Sørnes, Anders; Holte, Espen; Grenne, Bjørnar Leangen & Espeland, Torvald [Show all 10 contributors for this article] (2023). Aberration correction in 3D echocardiography . Show summary

  3D imaging is increasingly used in echocardiography. However, aberrations caused by sound speed variations in the body wall, degrades image quality, thereby compromising accurate diagnosis. Research into methods for compensating aberrations in pulse-echo imaging, referred to as aberration correction (AC), has been ongoing for more than 40 years. An AC algorithm has been developed and implemented to run real-time on a clinical ultrasound system for both 2D and 3D imaging. The algorithm estimates and corrects arrival time errors across all subapertures in a matrix array probe. A clinical trial has been carried out with the aim to evaluate the efficacy of our AC algorithm in improving image quality for 3D transthoracic echocardiography.

• Smistad, Erik (2023). Medisinsk bildeanalyse med kunstig intelligens.
• Wangensteen, Magnus; Johansen, Tonni Franke; Fatemi, Ali & Viggen, Erlend Magnus (2023). Ultrasonic Guided Waves and Machine Learning for Corrosion Monitoring in Steel Pipes. Show summary

  In a pipe, a circumferentially travelling ultrasonic wave will gather information about the properties and boundaries of the propagation medium. However, the compounded effects of diagnostic features like uniform pipe wall thinning, surface roughness, regional depressions, and pit developments are difficult to separate using traditional methods. Therefore, this study proposes an approach using artificial neural networks to estimate the diagnostic features of interest. This study is based on ultrasound simulations and synthetic data. The synthetic data is recorded at a set of transducer positions at the outer pipe wall. The resulting traces are then combined into 2D images where each vertical line represents a trace and thus a transducer location. The resulting images are used to train a neural network to extract relevant features. Diagnostic features for mean and minimum thickness, as well as roughness, are quite accurately estimated. Features for depth and location of depressions and depth of pits are also informative but less accurate.

• Wifstad, Sigurd Vangen; Kildahl, Henrik Agerup; Holte, Espen; Grenne, Bjørnar Leangen; Dalen, Håvard & Løvstakken, Lasse (2023). Automatic Jet Flow Convergence Detection and Quantification from 2D Color Doppler Flow Using Deep Learning.
• Bryon, Vincent; Wifstad, Sigurd Vangen; Hu, Jieyu; Grønli, Thomas & Løvstakken, Lasse (2023). Automated Patient-Specific Left Ventricular Simulations for Cardiac Function Evaluation Using Image-Based Computational Fluid Dynamics and Color Flow Imaging.
• Wifstad, Sigurd Vangen; Indimath, Shivanandan; Bryon, Vincent; Avdal, Jørgen; Løvstakken, Lasse & Måsøy, Svein-Erik [Show all 7 contributors for this article] (2023). Can we use Deep Learning to extract important information from poor resolution Doppler images?
• Bryon, Vincent; Wifstad, Sigurd Vangen; Hu, Jieyu; Grønli, Thomas & Løvstakken, Lasse (2023). Simulating Blood Flow in the Heart: Enhancing Color Flow Imaging with Computational Fluid Dynamics.
• Salte, Ivar Mjåland; Østvik, Andreas; Olaisen, Sindre Hellum; Karlsen, Sigve; Dahlslett, Thomas & Smistad, Erik [Show all 13 contributors for this article] (2023). Response to “Minimal Detectable Change and Reproducibility of Echocardiographic Strain: Implications for Clinical Practice”. Journal of the American Society of Echocardiography. ISSN 0894-7317. doi: 10.1016/j.echo.2023.08.017.
• Viggen, Erlend Magnus (2023). Setting the story straight about how vibrating surfaces produce sound. Show summary

  Can all vibrating surfaces produce sound in an adjacent fluid? This is a basic question in acoustics. Books and courses teach that the nature of the pressure wave generated by a vibration depends on the ratio between the vibration's speed and the fluid's sound speed: Supersonic vibrations (where the vibration moves faster than the sound speed) radiate sound waves into the fluid, while subsonic vibrations (where the vibration moves slower) generate evanescent pressure waves that do not radiate and cling to the surface. During an applied research project, however, we found results at odds with this prevailing view, indicating that subsonic vibrations can also radiate sound waves. Furthermore, a handful of articles over the last 30 years have also found similar results. While these results challenge the prevailing view of sound radiation, no full fundamental physical explanation of this phenomenon was available. We provide this missing explanation by taking energy conservation fully into account in a quite straightforward radiation model. This model balances the sound wave radiated into the fluid with a necessary attenuation of the guided wave underlying the vibration. While this attenuation is neglected by the majority of explanations in the literature, it is the key to explaining subsonic sound radiation, because attenuated vibrations produce inhomogeneous sound waves that always radiate. We find that subsonic vibrations can radiate sound waves in many situations, depending on the properties of the guided wave and the fluid medium.

• Letnes, Jon Magne; Wisløff, Ulrik & Dalen, Håvard (2023). Heart Failure With Preserved Ejection Fraction: Exercise Deficiency or Ventricular Maladaptation to Metabolic Demands? JACC Cardiovascular Imaging. ISSN 1936-878X. doi: 10.1016/j.jcmg.2023.05.026.
• Nyberg, John Anders Tomas; Jakobsen, Even Olav; Østvik, Andreas; Holte, Espen; Stølen, Stian & Løvstakken, Lasse [Show all 8 contributors for this article] (2023). Determinants of left atrial reservoir strain in a large healthy population. European Heart Journal-Cardiovascular Imaging. ISSN 2047-2404.
• Olaisen, Sindre Hellum; Espeland, Torvald; Smistad, Erik; Hu, Jieyu; Pasdeloup, David Francis Pierre & Østvik, Andreas [Show all 14 contributors for this article] (2023). Automatic measurements of left ventricular volumes and ejection fraction by artificial intelligence reduces time-consumption and inter-observer variability. Full text in Research Archive
• Holte, Espen (2023). Implementering av guidelines - når anbefalinger utfordrer kapasitet?
• Sæbø, Sigbjørn; Dalen, Håvard; Nyberg, John; Jakobsen, Even Olav; Nes, Bjarne Martens & Grenne, Bjørnar Leangen [Show all 8 contributors for this article] (2023). The relation between left atrial and left ventricular size in a healthy population.
• Pettersen, Håkon Neergaard; Sæbø, Sigbjørn; Pasdeloup, David Francis Pierre; Olaisen, Sindre Hellum; Østvik, Andreas & Bøen, Gunn Catrin Fossum [Show all 14 contributors for this article] (2023). The impact of real-time guiding by deep learning on test-retest variability of automated left ventricular systolic function measurements.
• Holmstrøm, Vegard; Smistad, Erik; Nyberg, John; Østvik, Andreas; Holte, Espen & Løvstakken, Lasse [Show all 8 contributors for this article] (2023). Deep Learning for Automated Analyses in the PLAX View.
• Dalen, Håvard (2023). Bioprotese med høy hastighet. HALT? Hva gjør vi?
• Pettersen, Håkon Neergaard; Sæbø, Sigbjørn; Pasdeloup, David Francis Pierre; Smistad, Erik; Østvik, Andreas & Olaisen, Sindre Hellum [Show all 14 contributors for this article] (2023). The Impact of Real-time Guiding by Deep Learning on Inter-operator Variability of Left Ventricular Function Measurements.
• Gopinath, Anoop; Ytterdal, Trond; Yadhav, Avinash; Lee, John; Rizkalla, Maher & Kumar, Mukesh (2023). SRAM Vmin Scaling Via Negative Wordline.
• Balasubramanian, Linknath Surya; Rizkalla, Maher; Lee, John; Ytterdal, Trond & Kumar, Mukesh (2023). Towards No Penalty Control Hazard Handling.
• Kasongo, Muana; Ytterdal, Trond; Lee, John; Rizkalla, Maher & Kumar, Mukesh (2023). Evaluation of Leakage Currents in Memristor Crossbar Arrays.
• Shur, Michael S.; Liu, Xueqing & Ytterdal, Trond (2023). Switching Characteristics of GaN Power Transistors.
• Shur, Michael S.; Liu, Xueqing & Ytterdal, Trond (2023). Phase-sensitive Silicon CMOS TeraFETs.
• Fadnes, Solveig (2023). High Frame Rate Imaging in Pediatric and Fetal Medicine - Opportunities and Challenges. Show summary

  This was an invited talk to the IEEE International Ultrasonics Symposium 2023 in Montréal, Canada. The talk summarized the research possibilities in pediatric and fetal medicine given by high frame rate imaging with focus on the visualization and quantification of intracardiac blood flow. Current clinical state-of-the-art imaging technology was demonstrated, and both the opportunities of new pathophysiological knowledge and diagnostic tools, and the inherent challenges of high-frame-rate imaging was discussed.

• Viggen, Erlend Magnus & Arnestad, Håvard (2023). Explaining the cutoff, reappearance, and persistence of subsonic leaky A0 Lamb waves.
• Fadnes, Solveig (2023). Vector Flow Imaging and extracted flow features.
• Balasubramanian, Linknath Surya; Cochran, Zachary; Rizkalla, Maher; Lee, John & Ytterdal, Trond (2023). Ultra Low-Power Low-Noise GNRFET Wideband Amplifier for Cryogenic Applications.
• Liu, Xueqing; Ytterdal, Trond & Shur, Michael S. (2023). Compact SPICE models for TeraFETs.
• Nyberg, John; Jakobsen, Even Olav; Østvik, Andreas; Holte, Espen; Stølen, Stian & Løvstakken, Lasse [Show all 8 contributors for this article] (2023). Left atrial strain in a large healthy population.
• Nyberg, John; Jakobsen, Even Olav; Østvik, Andreas; Holte, Espen; Stølen, Stian & Løvstakken, Lasse [Show all 8 contributors for this article] (2023). Determinants of left atrial reservoir strain in a large healthy population.
• Viggen, Erlend Magnus (2023). AI som bidrar til å unngå miljøkatastrofer. Show summary

  Sammen med Equinor har vi bygd en AI-basert assistent for Equinors loggtolkere, som de nå bruker i sitt daglige arbeid.

• Shur, Michael S.; Liu, Xueqing & Ytterdal, Trond (2022). Plasmonic Si CMOS TeraFETs for detection, mixing, and processing sub-THz radiation.
• Shur, Michael S.; Liu, Xueqing & Ytterdal, Trond (2022). Improved Thin Film Transistor Model Predicts TFT Operation in the THz Range.
• Yadhav, Avinash; Rizkalla, Maher; Ytterdal, Trond; Lee, John H.; Balasubramanian, Linknath Surya & Gopinath, Anoop (2022). Evaluation of FinFET in Ultra Low Power ALU.
• Liu, Xueqing; Shur, Michael S. & Ytterdal, Trond (2022). Optimization of Si CMOS TeraFETs for 300 GHz band operation.
• Mawad, Wadi & Nyrnes, Siri Ann (2024). Right ventricular energetics using blood speckle tracking in pediatric congenital heart disease. NTNU Grafisk senter.
• Pasdeloup, David Francis Pierre; Løvstakken, Lasse; Smistad, Erik & Dalen, Håvard (2023). Deep Learning in the Echocardiography Workflow: Challenges and Opportunities. Norges teknisk-naturvitenskapelige universitet. ISSN 978-82-326-7480-0.

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