93 research outputs found
Datafusie voor een betere visualisatie van echocardiografie
No full textEchocardiography (echo) is the modality of choice for routine clinical examinations of the heart. It is cost effective, portable, provides real time feedback, has a quick acquisition time and does not use ionizing radiation. The development of 3D echo in particular has brought added value in clinical examinations due to the ability to show the complex spatial relationship between structures. Despite the advantages, the modality is still confronted with limitations. These limitations include the dependency of the appearance of structures on the insonification angle, the spatially limited acquisition window for organs such as the heart, the reciprocity between the field of view (FOV) and the resolution, and the possibility of artifacts from signal dropouts.
In this thesis work, a solution was proposed to alleviate some of these limitations through image post processing. The aim was to enhance the visualization of echo images so that the workflow in the examination can be improved. The proposed solution to achieve the aforementioned aim was data compounding which is a method that combines images from several 3D echo acquisitions to form one enhanced FOV image. The data compounding solution consisted of registration and fusion wherein the images were brought to alignment through registration and the overlapping voxels were effectively combined through the rules of fusion. The study looked at the existing state-of-the-art methods for 3D echo registration defined for fusion. From the study it was noted that the registration for echo images requires alignment in both spatial and temporal dimension. Building upon the existing methods, both spatial and temporal registration methods were developed.
The developed spatial registration method used a multiscale iterative Farnebäck optic flow method which is analytically robust to local brightness changes, therefore making it suitable to the application on ultrasound images whose appearance could differ by changing insonification angle. Complementing the spatial registration, the temporal registration method was developed using an image-based measurement. Hereto, the temporal normalized cross correlation (NCC) curve, which had been shown by previous studies to resemble the left ventricle (LV) volume curve, was used to represent the events in the cardiac cycle. The temporal registration method utilized a piecewise spline-based method which interpolates the temporal NCC curves using a cubic B-spline for each cardiac phase (systolic and diastolic) while minimizing the squared distances between the curves. The developed registration method is fully image-based, making it independent from any additional apparatus such as an electromagnetic or optical tracking device.
The registration method was validated using data sets from simulations, in vivo transthoracic echo (TTE) and in vivo transesophageal echo (TEE). The simulation data set allowed the evaluation of the method against a known ground truth while the in vivo ones provided an indication of the performance in real clinical cases. The results showed that the spatial registration method was able to perform within the inter observer variation in manual annotation and the temporal accuracy was within the resolution of the echo recording. The spatial registration method was also applied for TEE anatomical view stabilization where the results were rated by trained observers to be a significant increase in the stability of TEE views. In terms of the FOV enhancement, the validation using TTE images resulted in an increase of the FOV of up to 25%. The results suggested that the method can successfully be applied for the enhancement of FOV and anatomical view stabilization, hence it has the potential to improve the workflow of 3D echo examinations. Although only the registration part of data compounding was developed, a possible method for fusion was proposed along with other suggestions for improvements in the future work. In addition, the versatility of the developed method was demonstrated by applying it to fluorescence images of the lymphatic system.status: Publishe
Adebiyi etal: absorption of shortwave radiation by North African dust
No full textThe codes and datasets contained here are for the paper with the information below
Titled: "North African dust absorbs substantially less solar radiation than estimated by climate models and remote-sensing retrievals"
Author: Adeyemi A. Adebiyi, Yue Huang, Bjørn H. Samset and Jasper F. Kok
Please see the ReadMe.txt for additional details.
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Corresponding Authors:
Adeyemi Adebiyi
Email: [email protected];
Department of Life and Environmental Sciences,
University of California-Merced,
5200 North Lake Road Merced, CA 95343
Incentives and politics: The perverse incentives paradox: root cause of many other paradoxes; the case of the Dutch Betuweroute
No full textThe transport system in general, and, more specifically, transport infrastructure projects as part of that system, has major impacts on society. This chapter elaborates on the question as to what extent the results can be transferred to other contexts. Because of the positive decision to build, combined with a lack of understanding of the rationale and no clear and neutral assessment of the pros and cons of the line, many people felt manipulated, although on the positive side, the process also contributed to important improvements in decision-making procedures. This chapter departs from what Samset and Volden refer to as ‘the paradox of perverse incentives’: public investments with no financial obligations for the target group may cause perverse incentives and result in counterproductive projects. It also makes clear that many things went wrong, such as having no clear explanation of the problems the line was supposed to solve, or the related challenges.Transport and Logistic
The Effect of Influence Attempts Using Consultation in Lateral Relations
No full textExecutive Master of Management i Påvirkninger og makt i lederrollen fra Handelshøyskolen BI, 2023While managers may use their power over subordinates to achieve desired outcomes, influence tactics to “manage your manager” have been given increased attention. This study focuses on influence in lateral relations, where data is scarce.
An experiment was conducted using an online survey to test different tactics aimed at garnering support for a proposal. Participants were randomly assigned to one of three groups: Critique, Advice, and Control. The survey presented a scenario in which a peer (a co-worker at the same level in the organization) presented a proposal. In the Control group, no influence attempt was made to gain support for the proposal. Two different variations of consultation as an influence tactic were used in the Critique and Advice groups. In the Critique group,
participants were asked to provide three to five critical comments on the proposal. Participants in the Advice group were asked to provide three to five suggestions for improving the proposal. The final question to all participants was to rate the level of support they would give the proposal.
A total of 230 participants completed the survey. When the Critique and the Advice group were combined into a single entity referred to as the Combined consultation group, no statistically significant difference in the level of support for the proposal was observed when compared to the Control group. However, when examining the three groups independently, the Advice group exhibited a significantly higher level of support for the proposal than the Control group, whereas the Critique group demonstrated a significantly lower level of support in comparison to the Control group. In conclusion, using consultation as an influence tactic to get support for a proposal is effective when consultation is sought by asking for advice. When consultation is sought by asking for critique, the targets tend to give lower levels of support for the proposal compared to not making an influence attempt at all
A virtual environment for navigating and controlling intraoperative magnetic resonance images
No full textEvaluation of a multi-view autostereoscopic real-time 3D ultrasound system for minimally invasive cardiac surgery guidance
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