Ole Marius Hoel Rindal

• MS, Robotics and intelligent systems/signal processing
• PhD Student at University of Oslo

The purpose of this work is to demonstrate a robust and clinically validated method for correcting sound speed aberrations in medical ultrasound. We propose a correction method that calculates focusing delays directly from the observed two-way distributed average sound speed. The method beamforms multiple coherence images and selects the sound spee...

In ultrasound imaging, speckle originates from a large amount of sub-resolution scatterers within the medium. In idealized cases, the speckle envelope statistics follow a Rayleigh distribution, but in practical pulse-echo imaging, the distribution depends on both the imaging system and the underlying tissue structure. Estimating envelope statistics...

REFoCUS (Retrospective Encoding For Conventional Ultrasound Sequences) offers great flexibility by enabling synthetic aperture beamforming from conventional ultrasound sequences. This flexibility is beneficial for many aspects in medical ultrasound beamforming, including e.g . combination of different transmit waves, distributed sound speed estim...

In beamforming, retrospective change in sound speed and recalculation of focusing delays is attractive both for improving image quality and for using it in an iterative image quality optimization process. Modifying the speed of sound retrospectively for focused transmits is challenging because the transmit focus position is a function of sound spee...

p>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...

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 require localization of specific regions and targets in the image such as a region of interest (ROI), a background region, and/or a point scat...

Background: An aberration correction algorithm has been implemented and demonstrated in an echocardiographic clinical trial using two-dimensional (2D) imaging. The method estimates and compensates arrival time errors between different sub-aperture processor (SAP) signals in a matrix array probe. Methods: Five standard views of channel data cinel...

p>The ultrasound image quality is of utmost importance for a clinician to reach the correct diagnosis. Conventionally, image quality is evaluated using metrics to evaluate 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 poi...

p>The ultrasound image quality is of utmost importance for a clinician to reach the correct diagnosis. Conventionally, image quality is evaluated using metrics to evaluate 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 poi...

No PDF available ABSTRACT Software beamforming allows flexible adaptive beamformers with great popularity and exponential growth in the number of papers published. Software beamforming can be a blessing to the image quality since access to raw channel data allows algorithms that better exploit the data. However, software beamforming can also be con...

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...

Objective: Wearable cuff-less blood pressure (BP) devices may overcome cuff limitations and offer continuous non-invasive BP monitoring. However, their accuracy in different clinical settings is not yet clarified. This study aimed to evaluate the accuracy of mean arterial pressure (MAP) measurements from a novel continuous cuff-less chest belt aga...

div> An aberration correction algorithm has been implemented and demonstrated in an echocardiographic clinical trial using 2D imaging. The method estimates and compensates arrival time errors between different sub- aperture processor signals in a matrix array probe in post processing. Five standard views of channel data cineloops were recorded fr...

div> An aberration correction algorithm has been implemented and demonstrated in an echocardiographic clinical trial using 2D imaging. The method estimates and compensates arrival time errors between different sub- aperture processor signals in a matrix array probe in post processing. Five standard views of channel data cineloops were recorded fr...

Objective: Pulse arrival time (PAT) is a potential main feature in cuff-less blood pressure (BP) monitoring. However, the precise relationship between BP parameters and PAT under varying conditions lacks a complete understanding. We hypothesize that simple test protocols fail to demonstrate the complex relationship between PAT and both SBP and DBP...

Objective Automated cuff-based blood pressure (BP) monitoring is limited to intermittent measurements vulnerable to movement. Pulse arrival time (PAT), calculated using electrocardiography (ECG) and photo plethysmography (PPG), has shown promise for non-invasive, continuous BP monitoring. The precise relationship between BP parameters and PAT under...

In the last 30 years the contrast-to-noise ratio (CNR) has been used to estimate contrast and lesion detectability in ultrasound images. Recent studies have shown that the CNR can not be used with modern beamformers, as dynamic range alterations can produce arbitrarily high CNR values with no real effect on the probability of lesion detection. We g...

Cross-country skiing is a popular Olympic winter sport, which is also used extensively as a recreational activity. While cross-country skiing primarily is regarded as a demanding endurance activity it is also technically challenging, as it contains two main styles (classical and skating) and many sub-techniques within these styles. To further under...

The processing power in commercially available hand-held devices has improved dramatically in recent years. In parallel, techniques used in high frame-rate medical ultrasound imaging, specifically plane-wave imaging, have reduced the number of ultrasound transmissions and amount of data necessary to reconstruct an ultrasound image. In combination,...

Many adaptive beamformers claim to produce images with increased contrast, a feature that could enable a better detection of lesions and anatomical structures. Contrast is often quantified using the contrast ratio (CR), and the contrast to noise ratio (CNR). The estimation of CR and CNR can be affected by dynamic range alterations (DRA), such as th...

Ultrasound is frequently used in conjunction with mammography in order to detect breast cancer as early as possible. However, due largely to the heterogeneity of breast tissue, ultrasound images are plagued with clutter that obstructs important diagnostic features. Short-lag spatial coherence (SLSC) imaging has proven to be effective at clutter red...

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,...

Data and analyses conducted in this study. (XLSX)

Many adaptive algorithms claim to provide higher contrast than delay-and-sum (DAS). These claims are often backed by estimations of the contrast-to-noise ratio (CNR). Intuitively , we assume that higher CNR leads to higher probability of lesion detection, and this is indeed the case for DAS. However, non-linear processing can arbitrarily alter CNR,...

The UFF taskforce works on the definition of an open file format for channel data and beam-formed data to facilitate dissemination of data, replication of research results, and comparison of processing techniques. Here we present the first draft of the UFF. HDF5 Hierarchical Data Format (HDF5) was chosen since it can store and organize large amou...

The lack of a standard format for storing ultrasound research data is hindering our ability to share and compare research results. This is slowing down the progress in our field, making it difficult to assess the relevance of new techniques. In October 2017 the Ultrasound File Format (UFF) initiative was formed with the aim of defining such a stand...

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 corre...

The Filtered-Delay-Multiply-And-Sum (F-DMAS) beamformer has recently been presented in the context of medical ultrasound image formation. This nonlinear beamformer produces images with improved contrast resolution and noise rejection when compared to the Delay-And-Sum (DAS) beamformer. In an attempt to better understand the origin of the improved i...

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...

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 sa...

We are in the middle of a Cambrian explosion. Software beamforming has redefined what can be done with the signal. As a consequence, our field has become flooded with adaptive beamforming (AB) algorithms, methods that by clever manipulation of channel data have exceeded our wildest expectations for the maximum achievable contrast and resolution. Or...

In this work, in vivo ultrasound cardiac images created with Capon's minimum variance adaptive beamformer are compared with images acquired with the conventional delay-and-sum beamformer. Specifically, we provide three views of a human heart imaged through the parasternal short-axis, the parasternal long-axis and the apical four-chamber views. The...

Recent progress in hardware and computing power has lead to an increased interest in adaptive beamforming for sonarimaging. Several algorithms that for each pixel scale the original sonarimage with a coherence estimate of the received data have been proposed. All of these algorithms claim to improve both contrast and resolution. Close examination o...

We are in the middle of a Cambrianexplosion.Softwarebeamforming has redefined what can be done with the signal. As a consequence, our field has become flooded with adaptive beamforming (AB) algorithms, methods that by clever manipulation of channel data have exceeded our wildest expectations for the maximum achievable contrast and resolution. Or ha...

All adaptive beamformers aim at increased resolution and better contrast ratio. However, stretching the dynamic range (e.g. 40log(x)) may produce the same effects. Adaptive beamformers are often tested on wire targets or uniform cysts, which do not allow the study of dynamic range (DR) alterations. DR stretching may possibly account for some of the...

This work describes the implementation of software plane-wave beamforming performed on the GPU of an Apple iPhone 6s and 6s Plus. The code can run on any current iOS device that supports the Metal API. The implementation is largely written in Swift, with some Objective-C, while the core processing component was written in Metal, Apple's new GPU pro...

This paper investigates the contrast improvements seen when using adaptive (Capon) beamforming to create ultrasound images. Ultrasound images of cysts have been simulated using linear array imaging in Field II. The contrast of the cyst compared to the speckle surrounding it has been investigated, especially the improved edges produced by the Capon...