88 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
Eigil Greve Knuth, 1903-1996
No full text... Count Eigil Knuth was born on 8 August 1903 at Klampenborg, an affluent community 10 km north of Copenhagen, the son of captain Eigil Greve Knuth and Djimphna, nee Gamel. ... Knuth was always of an uneasy mind, which was especially visible when he was younger. He graduated from one of Copenhagen\u27s oldest, best, and most distinguished high schools (gymnasium), but instead of attending the university, he continued at a technical school for apprentices to gain admission to the building technique school of the Academy of Fine Arts, where he spent the years from 1922 to 1924. He then moved to Italy for three years to study sculpture. Back in Denmark, he spent a year at Niels Buck\u27s Gymnastic Folk High School and graduated as a gymnastics teacher in the spring of 1932. That same summer, he participated for the first time in the excavating of old Norse ruins in West Greenland, assisting Dr. Aage Roussel from the National Museum. ... During the summer of 1934, he was excavating old Norse ruins, this time at Igaliko, again assisting Dr. Roussel and also Dr. Poul Norlund. In 1935 he was archaeologist on the Courtauld Expedition to East Greenland, during which Gunbjorns Fjeld, Greenland\u27s highest mountain, was climbed. There Knuth was assisting Dr. Helge Larsen from the National Museum, and without doubt their discussions had an important impact on Knuth the future archaeologist. ... During the Courtauld expedition, Knuth had many talks with Ebbe Munck, in which they agreed that their generation owed the nation a Danish expedition comparable to the Danmark Ekspedition 1906-08. ... As soon as the war was over, Knuth and Munck began to organize the contemplated expedition to Peary Land. Paid for by the newly established Danish Expedition Foundation, it would be the first in a long row of Peary Land Expeditions headed by Knuth. ... [The expedition house "Bronlund Hus" was built at Bronlund Fjord and from it many sledge and hiking trips were carried out which resulted in many archaeology discoveries.] However, Knuth deserves most credit for the demonstration of his, as he called them, Independence I and Independence II cultures, two immigration waves, almost 3000 years apart, of Palaeoeskimos, who migrated from Canada over northern Greenland and down the northern part of East Greenland. Independence I is most likely a branch of the oldest Saqqaq culture, whereas Independence II may be an early phase of the Dorset culture. ... Eigil Knuth was a very complex character. He was the artist par excellence; he was the author of several books, many papers, and numerous articles. ... His descriptions of Greenland landscapes, for instance, are masterpieces in beauty of sterling value. He was a sculptor with his own characteristic style and also a draftsman and a painter. He was a philosopher but also an exact scientist. ... Knuth\u27s Peary Land Expeditions ended in 1995, when he visited his beloved Bronlund Hus, his headquarters for so many years, for the last time. ..
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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2D LOCALIZATION OF SPECULAR REFLECTIONS USING ULTRASOUND
No full textImage guidance during cardiac interventions is primarily performed using X-ray fluoroscopy. For some applications, fluoroscopy may be complemented or possibly replaced by ultrasound imaging. However, good visualization of catheters and guide wires can be challenging using ultrasound. In this paper we present a novel method to locate and track a metallic device in real time using two-dimensional ultrasound. The method exploits channel data to identify specular reflections. An approach to characterize the directional echo and differentiate from diffuse backscattering is evaluated. Spatially resolved images are generated with directional properties of the specular objects depicted. The proposed method has been evaluated experimentally using a linear probe. Results of this method showed that the location as well as the angular orientation of a specular reflector can be detected provided its orientation is within a given range.status: Publishe
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