Ole Marius Hoel Rindal

• Kvalevåg, Magnus; Vrålstad, Anders Emil; Rindal, Ole Marius Hoel; Bjåstad, Tore Grüner; Dénarié, Bastien & Kristoffersen, Kjell [Vis alle 8 forfattere av denne artikkelen] (2023). vbeam: A Fast and Differentiable Beamformer for Optimizing Ultrasound Imaging. Proceedings - IEEE Ultrasonics Symposium. ISSN 1948-5719. doi: 10.1109/IUS51837.2023.10307255. Vis sammendrag

  We present vbeam: a new open-source beamforming library that provides fast parallel beamforming computation on the CPU and GPU for modern imaging setups. It is auto-differentiable which allows for incorporating image optimization and machine learning (ML) into the beamformer, and vice versa. The library can be used from either Python or MATLAB and aims to be a beamforming research tool which can be used stand-alone or integrated with tools, such as USTB, Field II and MUST.

• 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), s. 1295–1307. doi: 10.1109/TUFFC.2023.3308034. Fulltekst i vitenarkiv Vis sammendrag

  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

• Måsøy, Svein-Erik; Dénarié, Bastien Emmanuel; Sørnes, Anders Rasmus; Holte, Espen; Grenne, Bjørnar Leangen & Espeland, Torvald [Vis alle 10 forfattere av denne artikkelen] (2023). Aberration correction in 2D echocardiography. Quantitative Imaging in Medicine and Surgery (QIMS). ISSN 2223-4292. 13(7), s. 4603–4617. doi: 10.21037/qims-22-895.
• Arnestad, Håvard; Austeng, Andreas; Näsholm, Sven Peter & Rindal, Ole Marius Hoel (2022). The Effect of Retrospective Transmit Focusing on Minimum Variance Beamforming. Proceedings - IEEE Ultrasonics Symposium. ISSN 1948-5719. doi: 10.1109/IUS54386.2022.9958050. Vis sammendrag

  Minimum variance (MV) beamforming is a well-known adaptive beamforming approach. Retrospective transmit beamforming (RTB), on the other hand, is a technique implemented in some modern ultrasound scanners that strives to obtain two-way focus everywhere in the imaged region. However, it is not immediately clear how these methods should be combined in the image reconstruction pipeline. In this work, we suggest a general and efficient implementation for combining MV with RTB, and we study a few effects and synergetic benefits in comparison to multiple line acquisition processing and conventional delay-and-sum beamforming. Our finding is that RTB improves the resolution and robustness of MV beamforming outside the focal zone.

• Heimark, Sondre; Bøtker-Rasmussen, Kasper; Rindal, Ole Marius Hoel; Seeberg, Trine Margrethe; Stepanov, Alexey & Boysen, Elin Sundby [Vis alle 10 forfattere av denne artikkelen] (2022). COMPARISON OF CONTINUOUS MEAN ARTERIAL PRESSURE BY A WEARABLE CUFF-LESS DEVICE AGAINST INTRA-ARTERIAL MEASUREMENTS. Journal of Hypertension. ISSN 0263-6352. 40(1), s. e107–e108. doi: 10.1097/01.hjh.0000836332.51137.4c.
• Heimark, Sondre; Eitzen, Ingrid; Vianello, Isabella; Bøtker-Rasmussen, Kasper; Mamen, Asgeir & Rindal, Ole Marius Hoel [Vis alle 9 forfattere av denne artikkelen] (2022). Blood Pressure Response and Pulse Arrival Time During Exercise Testing in Well-Trained Individuals. Frontiers in Physiology. ISSN 1664-042X. 13. doi: 10.3389/fphys.2022.863855. Fulltekst i vitenarkiv Vis sammendrag

  Introduction: There is a lack of data describing the blood pressure response (BPR) in well-trained individuals. In addition, continuous bio-signal measurements are increasingly investigated to overcome the limitations of intermittent cuff-based BP measurements during exercise testing. Thus, the present study aimed to assess the BPR in well-trained individuals during a cycle ergometer test with a particular focus on the systolic BP (SBP) and to investigate pulse arrival time (PAT) as a continuous surrogate for SBP during exercise testing. Materials and Methods: Eighteen well-trained male cyclists were included (32.4 ± 9.4 years; maximal oxygen uptake 63 ± 10 ml/min/kg) and performed a stepwise lactate threshold test with 5-minute stages, followed by a continuous test to voluntary exhaustion with 1-min increments when cycling on an ergometer. BP was measured with a standard automated exercise BP cuff. PAT was measured continuously with a non-invasive physiological measurements device (IsenseU) and metabolic consumption was measured continuously during both tests. Results: At lactate threshold (281 ± 56 W) and maximal intensity test (403 ± 61 W), SBP increased from resting values of 136 ± 9 mmHg to maximal values of 219 ± 21 mmHg and 231 ± 18 mmHg, respectively. Linear within-participant regression lines between PAT and SBP showed a mean r2 of 0.81 ± 17. Conclusion: In the present study focusing on the BPR in well-trained individuals, we observed a more exaggerated systolic BPR than in comparable recent studies. Future research should follow up on these findings to clarify the clinical implications of the high BPR in well-trained individuals. In addition, PAT showed strong intra-individual associations, indicating potential use as a surrogate SBP measurement during exercise testing.

• Heimark, Sondre; Rindal, Ole Marius Hoel; Seeberg, Trine Margrethe; Stepanov, Alexey; Boysen, Elin Sundby & Bøtker-Rasmussen, Kasper [Vis alle 11 forfattere av denne artikkelen] (2021). Blood pressure altering method affects correlation with pulse arrival time. Blood Pressure Monitoring. ISSN 1359-5237. doi: 10.1097/MBP.0000000000000577. Fulltekst i vitenarkiv
• Rindal, Ole Marius Hoel; Rodriguez-Molares, Alfonso & Austeng, Andreas (2020). Resolution Measured as Separability Compared to Full Width Half Maximum for Adaptive Beamformers. Proceedings - IEEE Ultrasonics Symposium. ISSN 1948-5719. doi: 10.1109/IUS46767.2020.9251787. Fulltekst i vitenarkiv
• Rodriguez-Molares, Alfonso; Rindal, Ole Marius Hoel; D´Hooge, Jan; Måsøy, Svein-Erik; Austeng, Andreas & Bell, Muyinatu A. Lediju [Vis alle 7 forfattere av denne artikkelen] (2020). The Generalized Contrast-to-Noise Ratio: A Formal Definition for Lesion Detectability. IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control. ISSN 0885-3010. 67(4), s. 745–759. doi: 10.1109/TUFFC.2019.2956855. Fulltekst i vitenarkiv
• Rindal, Ole Marius Hoel; Rodriguez-Molares, Alfonso; Måsøy, Svein-Erik & Bjåstad, Tore Grüner (2019). Improved Lesion Detection Using Nonlocal Means Post-Processing. Proceedings - IEEE Ultrasonics Symposium. ISSN 1948-5719. 2019-October, s. 1013–1016. doi: 10.1109/ULTSYM.2019.8926303. Fulltekst i vitenarkiv
• Rindal, Ole Marius Hoel; Austeng, Andreas; Fatemi, Ali & Rodriguez-Molares, Alfonso (2019). The Effect of Dynamic Range Alterations in the Estimation of Contrast. IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control. ISSN 0885-3010. 66(7), s. 1198–1208. doi: 10.1109/TUFFC.2019.2911267.
• Tjønnås, Johannes; Seeberg, Trine Margrethe; Rindal, Ole Marius Hoel; Haugnes, Pål & Sandbakk, Øyvind (2019). Assessment of Basic Motions and Technique Identification in Classical Cross-Country Skiing. Frontiers in Psychology. ISSN 1664-1078. 10. doi: 10.3389/fpsyg.2019.01260. Fulltekst i vitenarkiv
• Palmer, Cameron Lowell & Rindal, Ole Marius Hoel (2019). Wireless, Real-Time Plane-Wave Coherent Compounding on an iPhone: A Feasibility Study. IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control. ISSN 0885-3010. 66(7), s. 1222–1231. doi: 10.1109/TUFFC.2019.2914555.
• Wiacek, Alycen; Falomo, Eniola; Myers, Kelly; Rindal, Ole Marius Hoel; Fabrega-Foster, Kelly & Harvey, Susan [Vis alle 7 forfattere av denne artikkelen] (2018). Clinical Feasibility of Coherence-Based Beamforming to Distinguish Solid from Fluid Hypoechoic Breast Masses. Proceedings - IEEE Ultrasonics Symposium. ISSN 1948-5719. 2018-January. doi: 10.1109/ULTSYM.2018.8579846.
• Bernard, Olivier; Bradway, David; Hansen, Hendrik H.G.; Kruizinga, Pieter; Nair, Arun & Perdios, Dimitris [Vis alle 11 forfattere av denne artikkelen] (2018). The Ultrasound File Format (UFF) - First Draft. Proceedings - IEEE Ultrasonics Symposium. ISSN 1948-5719. 2018-January:8579642, s. 1–4. doi: 10.1109/ULTSYM.2018.8579642.
• Rodriguez-Molares, Alfonso; Rindal, Ole Marius Hoel; D'Hooge, Jan R M; Måsøy, Svein-Erik; Austeng, Andreas & Torp, Hans (2018). The generalized contrast-to-noise ratio. Proceedings - IEEE Ultrasonics Symposium. ISSN 1948-5719. doi: 10.1109/ULTSYM.2018.8580101.
• Wiacek, Alycen; Rindal, Ole Marius Hoel; Falomo, Eniola; Myers, Kelly; Fabrega-Foster, Kelly & Harvey, Susan [Vis alle 7 forfattere av denne artikkelen] (2018). Robust Short-Lag Spatial Coherence Imaging of Breast Ultrasound Data: Initial Clinical Results. IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control. ISSN 0885-3010. 66(3), s. 527–540. doi: 10.1109/TUFFC.2018.2883427.
• Solli, Guro Strøm; Kocbach, Jan; Seeberg, Trine Margrethe; Tjønnås, Johannes; Rindal, Ole Marius Hoel & Haugnes, Pål [Vis alle 8 forfattere av denne artikkelen] (2018). Sex-based differences in speed, sub-technique selection, and kinematic patterns during low- and high-intensity training for classical cross-country skiing. PLOS ONE. ISSN 1932-6203. 13(11). doi: 10.1371/journal.pone.0207195. Fulltekst i vitenarkiv Vis sammendrag

  Objectives We investigated sex-based differences in speed, sub-technique selection, and kinematic patterns during low- (LIT) and high-intensity training (HIT) for classical cross-country (XC) skiing across varying terrain. Methods Six male and six female elite XC skiers with an approximately 15% differences in VO2max (men: 68.9±2.9 mL·min-1·kg-1, women: 60.1±3.3 mL·min-1·kg-1) were monitored using a multi-sensor system to collect time-synchronised data of heart rate, speed, and multiple tri-axial inertial measurements units while XC skiing on a 5-km competition track. Results Men skied 21% faster than women during HIT (5.9±0.3 m·s-1 vs. 4.9±0.2 m·s-1, P < .001), with the greatest difference (26%) while skiing on flat terrain, whereas skiing speed did not significantly differ between men and women during LIT. At similar instructed intensity and rating of perceived effort, women exhibited significantly higher relative heart rate (85±2% vs. 71±3% of maximum) and blood lactate levels (4.0±1.3 vs. 1.2±0.2 mmol/L) during LIT (all P < .001) than men, whereas physiological responses did generally not differ between the sexes during HIT. During both intensities and among both sexes, double poling (DP) was the sub-technique most used relative to distance, followed by miscellaneous sub-techniques (MISC), diagonal stride (DIA), kick double poling (DK) and herringbone (HRB). In relation to distance women used DIA more than men during LIT (22% vs. 17%, P = .009) and HIT (23% vs. 12%, P = .001), whereas men used MISC, including tucking and turning, more than women during LIT (39% vs. 25%, P = .017) and HIT (41% vs. 30%, P = .064). In particular, men used DP more than women while skiing the uphill sections during both LIT (24% vs. 11%, P = .015) and HIT (39% vs. 13%, P = .002). Conclusions Our findings provide novel insights into sex-based differences in speed, sub-technique selection, and kinematic patterns during LIT and HIT for classical skiing.

• Prieur, Fabrice Jean Gabriel; Rindal, Ole Marius Hoel & Austeng, Andreas (2018). Signal Coherence and Image Amplitude With the Filtered Delay Multiply and Sum Beamformer. IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control. ISSN 0885-3010. 65(7), s. 1133–1140. doi: 10.1109/TUFFC.2018.2831789. Fulltekst i vitenarkiv
• Rindal, Ole Marius Hoel; Seeberg, Trine Margrethe; Tjønnås, Johannes; Haugnes, Pål & Sandbakk, Øyvind (2018). Automatic Classification of Sub-Techniques in Classical Cross-Country Skiing Using a Machine Learning Algorithm on Micro-Sensor Data. Sensors. ISSN 1424-8220. 18(1). doi: 10.3390/s18010075. Fulltekst i vitenarkiv Vis sammendrag

  The automatic classification of sub-techniques in classical cross-country skiing provides unique possibilities for analyzing the biomechanical aspects of outdoor skiing. This is currently possible due to the miniaturization and flexibility of wearable inertial measurement units (IMUs) that allow researchers to bring the laboratory to the field. In this study, we aimed to optimize the accuracy of the automatic classification of classical cross-country skiing sub-techniques by using two IMUs attached to the skier’s arm and chest together with a machine learning algorithm. The novelty of our approach is the reliable detection of individual cycles using a gyroscope on the skier’s arm, while a neural network machine learning algorithm robustly classifies each cycle to a sub-technique using sensor data from an accelerometer on the chest. In this study, 24 datasets from 10 different participants were separated into the categories training-, validation- and test-data. Overall, we achieved a classification accuracy of 93.9% on the test-data. Furthermore, we illustrate how an accurate classification of sub-techniques can be combined with data from standard sports equipment including position, altitude, speed and heart rate measuring systems. Combining this information has the potential to provide novel insight into physiological and biomechanical aspects valuable to coaches, athletes and researchers

• Prieur, Fabrice Jean Gabriel; Rindal, Ole Marius Hoel; Holm, Sverre & Austeng, Andreas (2017). Influence of the Delay-Multiply-And-Sum beamformer on the ultrasound image amplitude. Proceedings - IEEE Ultrasonics Symposium. ISSN 1948-5719. doi: 10.1109/ULTSYM.2017.8092637.
• Hverven, Stine Myhre; Rindal, Ole Marius Hoel; Rodriguez-Molares, Alfonso & Austeng, Andreas (2017). The influence of speckle statistics on contrast metrics in ultrasound imaging. Proceedings - IEEE Ultrasonics Symposium. ISSN 1948-5719. s. 1–4. doi: 10.1109/ULTSYM.2017.8091875. Fulltekst i vitenarkiv
• Rodriguez-Molares, Alfonso; Rindal, Ole Marius Hoel; Bernard, Olivier; Nair, Arun; Bell, Muyinatu A. Lediju & Liebgott, Herve [Vis alle 8 forfattere av denne artikkelen] (2017). The UltraSound ToolBox. Proceedings - IEEE Ultrasonics Symposium. ISSN 1948-5719. doi: 10.1109/ULTSYM.2017.8092389. Fulltekst i vitenarkiv
• Rindal, Ole Marius Hoel; Rodriguez-Molares, Alfonso & Austeng, Andreas (2017). The dark region artifact in adaptive ultrasound beamforming. Proceedings - IEEE Ultrasonics Symposium. ISSN 1948-5719. doi: 10.1109/ULTSYM.2017.8092255. Fulltekst i vitenarkiv
• Hverven, Stine Myhre; Rindal, Ole Marius Hoel; Hunter, Alan Joseph & Austeng, Andreas (2017). Point scatterer enhancement in ultrasound by wavelet coefficient shrinkage. Proceedings - IEEE Ultrasonics Symposium. ISSN 1948-5719. 2017, s. 1–4. doi: 10.1109/ULTSYM.2017.8092971. Fulltekst i vitenarkiv
• Rindal, Ole Marius Hoel; Aakhus, Svend; Holm, Sverre & Austeng, Andreas (2017). Hypothesis of Improved Visualization of Microstructures in the Interventricular Septum with Ultrasound and Adaptive Beamforming. Ultrasound in Medicine and Biology. ISSN 0301-5629. 43(10), s. 2494–2499. doi: 10.1016/j.ultrasmedbio.2017.05.023.
• Seeberg, Trine Margrethe; Tjønnås, Johannes; Rindal, Ole Marius Hoel; Haugnes, Pål; Dalgard, Steffen Harald & Sandbakk, Øyvind (2017). A multi-sensor system for automatic analysis of classical cross-country skiing techniques. Sports Engineering. ISSN 1369-7072. 20(4), s. 313–327. doi: 10.1007/s12283-017-0252-z. Fulltekst i vitenarkiv Vis sammendrag

  Commercial systems utilizing data from inertial measurement units (IMUs) to analyse movement patterns have not yet been adapted to monitor daily training in cross-country (XC) skiing. The main purposes of this study are to investigate: (1) the feasibility and potential of a multi-sensor system consisting of a heart rate sensor, global navigation satellite systems (GNSSs) data and seven IMUs placed at multiple locations on the body for outdoor XC skiing, and (2) the validity of employing hard decision rules based on the correlation between arms and legs for detecting sub-techniques in classical XC skiing. All sensor data were synchronously sampled and synchronized with GNSS data from a commercially available sports watch while XC skiing on varying tracks, from amateur skiers and world-class athletes. An algorithm based on the correlation of the angular velocity of arms and legs was developed to detect the three main classic sub-techniques, diagonal, double poling with a kick and double poling. Other sub-techniques were classified as miscellaneous (0–20%). The system is shown to work well outdoors on snow during different conditions, and the implemented algorithm was validated by video analyses to detect the three sub-techniques with a sensitivity of 99–100%. This study is the first to detect and link sub-techniques in XC skiing to GNSS data, thereby associating the detection and distribution of sub-techniques to different terrains. Such information gives insight into the technical and tactical aspects of skiers’ daily training and competitions, thereby providing a tool for coaches and athletes.

• Rindal, Ole Marius Hoel & Austeng, Andreas (2016). Double Adaptive Plane-wave Imaging. Proceedings - IEEE Ultrasonics Symposium. ISSN 1948-5719. 2016-November. doi: 10.1109/ULTSYM.2016.7728906.
• Rindal, Ole Marius Hoel; Austeng, Andreas; Torp, Hans Garman; Holm, Sverre & Rodriguez-Molares, Alfonso (2016). The dynamic range of adaptive beamformers. Proceedings - IEEE Ultrasonics Symposium. ISSN 1948-5719. 2016-November. doi: 10.1109/ULTSYM.2016.7728717.
• Palmer, Cameron Lowell; Rindal, Ole Marius Hoel; Holm, Sverre & Austeng, Andreas (2016). Realtime plane-wave software beamforming with an iPhone. Proceedings - IEEE Ultrasonics Symposium. ISSN 1948-5719. 2016-November, s. 1–4. doi: 10.1109/ULTSYM.2016.7728408.
• Rindal, Ole Marius Hoel; Åsen, Jon Petter; Holm, Sverre & Austeng, Andreas (2014). Understanding contrast improvements from capon beamforming. Proceedings - IEEE Ultrasonics Symposium. ISSN 1948-5719. s. 1694–1697. doi: 10.1109/ULTSYM.2014.0420.

Se alle arbeider i Cristin

• Arnestad, Håvard; Rindal, Ole Marius Hoel; Austeng, Andreas & Näsholm, Sven Peter (2024). Estimation of probability densities in ultrasound imaging.
• Kvalevåg, Magnus; Vrålstad, Anders Emil; Rindal, Ole Marius Hoel; Bjåstad, Tore Grüner; Dénarié, Bastien & Kristoffersen, Kjell [Vis alle 8 forfattere av denne artikkelen] (2023). vbeam: A Fast and Differentiable Beamformer for Optimizing Ultrasound Imaging.
• 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. Vis sammendrag

  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.

• Rindal, Ole Marius Hoel (2023). Sonair introducing ADAR: 3D Acoustic Detection And Ranging in air.
• Rindal, Ole Marius Hoel; Fiorentini, Stefano; Avdal, Jørgen; Austeng, Andreas & Rodriguez Molares, Alfonso (2023). The Generalized Beamformer in the UltraSound ToolBox. Vis sammendrag

  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.

• Måsøy, Svein-Erik; Dénarié, Bastien Emmanuel; Sørnes, Anders; Holte, Espen; Grenne, Bjørnar Leangen & Espeland, Torvald [Vis alle 10 forfattere av denne artikkelen] (2023). Aberration correction in 3D echocardiography . Vis sammendrag

  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.

• Vrålstad, Anders Emil; Kvalevåg, Magnus; Rindal, Ole Marius Hoel & Måsøy, Svein-Erik (2023). Universal REFoCUS with Spatial Weighting. Vis sammendrag

  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.

• Näsholm, Sven Peter; Arnestad, Håvard; Austeng, Andreas & Rindal, Ole Marius Hoel (2023). Calculating the generalized contrast-to-noise ratio using kernel density estimation. Vis sammendrag

  The histogram-based generalized contrast-to-noise ratio (gCNR) evaluates how well image regions with different intensity can be distinguished. The gCNR is defined as ‘one minus the overlap region’ of normalized histograms from two regions. Histogram-based gCNR depends on user parameters like bin size and bin offset, but there are also approaches to robustify the histogram calculation. Kernel density estimation (KDE) is a well-established alternative to histograms to estimate probability density functions (PDFs), and is generally considered to be more robust. We suggest replacing histograms with KDE in gCNR calculations.

• Melteig, Elina & Rindal, Ole Marius Hoel (2023). Skiteknikk under lupen med sensordata og maskinlæring. Titan.uio.no.
• Rindal, Ole Marius Hoel; Gløersen, Øyvind & Tjønnås, Johannes (2023). Analyzing Micro Parameters of Diagonal Stride in Cross-country Skiing using Microsensors on Snow.
• Rindal, Ole Marius Hoel; Gløersen, Øyvind; Kvåle, Kaja Frøysaa; Tjønnås, Johannes & Liverud, Anders Erik (2023). Visualizing and Annotating Video and Microsensor Data from Cross-Country Skiing using the Autoactive Research Environment.
• Gløersen, Øyvind; Rindal, Ole Marius Hoel & Tjønnås, Johannes (2023). Digital Skiguru – Quantifying “Ski Feeling” using Microsensors.
• Vrålstad, Anders Emil; Rindal, Ole Marius Hoel; Bjåstad, Tore Grüner & Måsøy, Svein-Erik (2022). Sound Speed Correction for Virtual Source Retrospective Transmit Beamforming.
• Rindal, Ole Marius Hoel (2022). Transition of advanced techniques from medical ultrasound to sonar imaging using the UltraSound ToolBox.
• Austeng, Andreas; Arnestad, Håvard; Bjåstad, Tore Grüner; Måsøy, Svein-Erik & Rindal, Ole Marius Hoel (2022). Issues with Histogram Matching for Fair Evaluation of Image Quality Metrics.
• Rindal, Ole Marius Hoel; Bjåstad, Tore Grüner; Espeland, Torvald; Berg, Erik Andreas Rye & Måsøy, Svein-Erik (2022). Global Image Coherence (GIC) – an in-vivo Image Quality Metric.
• Rindal, Ole Marius Hoel; Vrålstad, Anders Emil; Bjåstad, Tore Grüner; Austeng, Andreas & Måsøy, Svein-Erik (2022). Coherence from REFoCUS compared to Retrospective Transmit Beamforming.
• Arnestad, Håvard; Austeng, Andreas; Näsholm, Sven Peter & Rindal, Ole Marius Hoel (2022). The Effect of Retrospective Transmit Focusing on Minimum Variance Beamforming.
• Gereb, Gabor; Hansen, Roy Edgar; Austeng, Andreas; Lønmo, Tor Inge Birkenes; Näsholm, Sven Peter & Rindal, Ole Marius Hoel (2022). Ultrasound Beamformer Benchmarking Pipeline.
• Gereb, Gabor; Hansen, Roy Edgar; Lønmo, Tor Inge Birkenes; Näsholm, Sven Peter; Austeng, Andreas & Rindal, Ole Marius Hoel (2022). Improving Sonar Surveying of Subsea Cables and Pipelines with Adaptive Beamforming. Vis sammendrag

  Background, Motivation and Objective Safe and efficient transportation of offshore energy requires well-maintained underwater infrastructure, no matter if the energy source is fossil, wind, sun, or wave. Subsea cables and pipelines can be efficiently surveyed using sonar systems mounted on surface or underwater vehicles. Adaptive array signal processing methods are increasingly explored to improve image quality and detection or estimation accuracy in specific survey scenarios. However, adaptive methods can be sensitive to the context they are used in. Therefore, choosing the right beamforming approach from the available candidates requires extensive testing in various scenarios, which is often not feasible out at sea. Statement of Contribution/Methods Realistic simulation of complex underwater scenarios has been previously demonstrated using the Field II Ultrasound Simulation Program in combination with the open access package UltraSound ToolBox (USTB). We use Field II to create digital twins of water column images from pipeline surveys, and then modify parameters such as the layout, depth, and SNR to extend the scope of testing. We add multiple realizations of random noise to the signal and then use USTB to beamform the data with different techniques. On the beamformed data we perform estimation of multiple parameters such as the position and size of the pipe and the seabed depth around it. Finally, using the known ground truth of the model, we compare the bias and variance of the estimations made using images reconstructed by different beamformers. Results/Discussion Following on the results of previous studies demonstrating the benefits of adaptive beamforming in sonar bathymetry, we present a benchmark study of adaptive beamforming techniques such as Low Complexity Adaptive (LCA) and Capon Minimum Variance (MVDR). Comparison with the Coherence Factor (CF) method is made as well. We use Delay-and-Sum (DAS) as a reference with various apodizations. We provide quantitative performance assessment based on the statistical distribution of the estimations with reference to the ground truth in different scenarios.

• Eitzen, Ingrid; Heimark, Sondre; Seeberg, Trine Margrethe; Bøtker-Rasmussen, Kasper; Mamen, Asgeir & Waldum-Grevbo, Bård [Vis alle 9 forfattere av denne artikkelen] (2022). Well-trained individuals have an exaggerated blood pressure response during exercise testing.
• Måsøy, Svein-Erik; Dénarié, Bastien; Sørnes, Anders; Holte, Espen; Grenne, Bjørnar & Espeland, Torvald [Vis alle 10 forfattere av denne artikkelen] (2022). Aberration Correction in the Echo Lab - A Clinical Pilot .
• Rindal, Ole Marius Hoel; Näsholm, Sven Peter; Hansen, Roy Edgar & Austeng, Andreas (2022). Compensating Dynamic Range Alterations from Adaptive Beamforming using Histogram Matching.
• Rindal, Ole Marius Hoel; Näsholm, Sven Peter; Hansen, Roy Edgar & Austeng, Andreas (2022). Image Enhancement Using Capon Minimum Variance Adaptive Beamforming in Synthetic Aperture Sonar.
• Austeng, Andreas; Näsholm, Sven Peter; Hansen, Roy Edgar & Rindal, Ole Marius Hoel (2022). Spatial Aperture Coherence with Synthetic Transmit Focusing in SAS.
• Rindal, Ole Marius Hoel (2021). The UltraSound Toolbox : Open source processing of ultrasound images with the UltraSound ToolBox. CIUS Annual Report 2020.
• Rindal, Ole Marius Hoel (2021). Open source processing of ultrasound images with the USTB. CIUS blogg: Innovations in Ultrasound - From the Centre for Innovative Ultrasound Solutions.
• Heimark, Sondre; Rindal, Ole Marius Hoel; Seeberg, Trine Margrethe; Stepanov, Alexey; Boysen, Elin Sundby & Bøtker-Rasmussen, Kasper [Vis alle 11 forfattere av denne artikkelen] (2021). Pulse Arrival Time Can Track Changes in Systolic Blood Pressure .
• Heimark, Sondre; Rindal, Ole Marius Hoel; Seeberg, Trine Margrethe; Stepanov, Alexey; Boysen, Elin Sundby & Bøtker-Rasmussen, Kasper [Vis alle 11 forfattere av denne artikkelen] (2021). PULSE ARRIVAL TIME CAN TRACK CHANGES IN SYSTOLIC BLOOD PRESSURE. Journal of Hypertension. ISSN 0263-6352. doi: 10.1097/01.hjh.0000745808.43316.c3.
• Berg-Hansen, Pål; Moen, Stine Marit; Jahren, Silje Ekroll; Klyve, Thomas; Meyer, Fredrik & Strisland, Frode [Vis alle 10 forfattere av denne artikkelen] (2020). Use of sensors in MS rehabilitation - a pilot study.
• VIANELLO, Isabella; Mamen, Asgeir; Heimark, Sondre; Sandbakk, Øyvind; Samani, Afshin & Rindal, Ole Marius Hoel [Vis alle 7 forfattere av denne artikkelen] (2020). BLOOD PRESSURE VARIATION AS INDICATOR OF AEROBIC PERFORMANCE.
• Rindal, Ole Marius Hoel (2020). Software Beamforming in Medical Ultrasound Imaging – A Blessing and a Curse.
• Seeberg, Trine Margrethe; Kocbach, Jan; Noordhof, Dionne; Danielsen, Jørgen; Haugnes, Pål & Skovereng, Knut [Vis alle 10 forfattere av denne artikkelen] (2020). COMPARISON OF SUB-TECHNIQUE UTILIZATION, KINEMATICS AND PHYSIOLOGICAL RESPONSES BETWEEN LOW- AND HIGH-INTENSITY ROLLER SKI SKATING.
• Danielsen, Dag Inge & Rindal, Ole Marius Hoel (2020). Ultralyd-forbedringer gir også utfordringer. Titan.uio.no.
• Tjønnås, Johannes; Seeberg, Trine Margrethe; Rindal, Ole Marius Hoel; Haugnes, Pål & Sandbakk, Øyvind (2019). Basic Motions and Technique Identification in Classical Cross-Country Skiing.
• Rindal, Ole Marius Hoel; Rodriguez-Molares, Alfonso & Austeng, Andreas (2018). A simple, artifact-free, virtual source model. Vis sammendrag

  Retrospective beamforming is a synthetic technique that, by combination of several converging waves, reduces the number of transmission events without reduction of image quality. However, due to a discontinuity in the conventional spherical virtual source model, an artifact occurs at the focal depth where the virtual sources are located. We correct the artifact by modifying the spherical model by assuming plane wave propagation in a region around the focal depth. This hybrid model is simpler and lighter than the current accepted solution.

• Seeberg, Trine Margrethe; Sandbakk, Øyvind; Tjønnås, Johannes; Rindal, Ole Marius Hoel & Kokkegård, Hanne (2018). Norges skiløbere kører suverænt på avanceret sensor-teknologi. Vis sammendrag

  Ny teknologi kan gøre brugen af video overflødig, fordi målingerne er så præcise. Og sensorerne virker ude på løjperne - ikke kun i laboratoriet.

• Seeberg, Trine Margrethe; Sandbakk, Øyvind; Tjønnås, Johannes; Rindal, Ole Marius Hoel & Benjaminsen, Christina (2018). Researchers are helping elite skiers to hone their performance. [Internett]. Gemini. Vis sammendrag

  Norwegian cross-country skiing is applying science to analyse how its elite athletes exploit their strengths during training and competition. The aims of this sensor-based research are to give skiers valuable advice about training and help them find the perfect pair of skis.

• Benjaminsen, Christina; Seeberg, Trine Margrethe; Sandbakk, Øyvind; Tjønnås, Johannes & Rindal, Ole Marius Hoel (2018). Ski-eliten kvesser teknikken med sensorer på kroppen. Gemini. ISSN 0802-085X. Vis sammendrag

  Norsk langrennssport går vitenskapelig til verks for å analysere hvordan våre gullhåp utnytter kreftene sine når de går på ski. Sensorbasert forskning skal gi løperne verdifulle treningstips og hjelpe dem med å finne det helt perfekte skipar.

• Rindal, Ole Marius Hoel & Bell, Muyinatu A. Lediju (2017). Short Lag Spatial Coherence beamforming in ultrasound imaging.
• Prieur, Fabrice Jean Gabriel; Rindal, Ole Marius Hoel; Holm, Sverre & Austeng, Andreas (2017). Influence of the Delay-Multiply-And-Sum beamformer on the ultrasound image amplitude.
• Rindal, Ole Marius Hoel; Seeberg, Trine Margrethe; Tjønnås, Johannes; Haugnes, Pål; Dalgard, Steffen Harald & Sandbakk, Øyvind (2016). Analysis of sub-techniques in classical cross-country skiing by employing machine learning algorithms on micro sensor data.
• Rindal, Ole Marius Hoel; Austeng, Andreas & Solberg, Anne H Schistad (2019). Software Beamforming in Medical Ultrasound Imaging - a blessing and a curse. Universitetet i Oslo. Fulltekst i vitenarkiv

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