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Final Report Summary - USART (Ultrasound guided cardiac arrythmia treatment)

Background
Every 30 seconds someone in the Western world suffers sudden cardiac death and/or death from heart failure. These two conditions remain the major challenges in modern cardiology. However, currently emerging treatments offer hope in fighting these events: triggers for rhythm disturbances in the heart can be destroyed by heat via ablation therapy, and pacemakers and defibrillators can be implanted to break up deadly fibrillation or ameliorate heart dysfunction. In order to bridge the gap between clinical needs and currently available technology for assessment of cardiac function and the underlying etiology there is a need to develop competence in Europe within this area.

Objectives
Through training and knowledge development in a focused research project, USART provided Europe with experienced researchers with the cross-disciplinary understanding and research skills necessary to develop enabling technologies in an industrial setting. The longer term outcome of the project consists of new products which will directly benefit patients across Europe by advancing the state of care related to several key issues within cardiology.
We had defined the following technical and clinical objectives that directed the coordinated set of training and research activities:
Breakthrough in dyssynchrony imaging
Ultrasound can provide amazing frame rates allowing cardiologists to study the rapid contraction of the heart as well as how heart valves move. However, abnormalities in the dyssynchronous heart require even higher frame rates than currently possible to study these short lived events. USART developed ultra-fast volumetric imaging techniques and methods to process this data reliably in 3D.
Improved outcome for cardiac ablation
Ablation therapy aims at destroying tissue in the heart that causes abnormal electrical conduction patterns. Ablation targets are typically pulmonary veins or the zone around infarcted areas. Today, ablation is successful in about 70% of the patients; however retreatments are necessary for about 50% of the patients. Our ambition was to improve this success rate by introducing real-time ultrasound guidance to monitor the treatment effect.

Progress
Ultra-fast ultrasound imaging
Ultra-fast ultrasound imaging can be performed by transmitting a wide (un-focused) ultrasound beam into tissue instead of many narrow beams. One type of wide beam is a diverging wave. The implementation of this method may be limited by the configuration of clinical 3D ultrasound probes. We tested diverging wave imaging in a commercial ultrasound system and tried to estimate velocities after off-line beam forming of the received signals. We were able to estimate tissue velocities with acceptable accuracy by optimizing the trade-off between image quality and frame rate.

Automatic image interpretation of the left atrium
For diagnosis, treatment planning and intra-operative guidance, it is important to have tools that can automatically interpret image features such as boundaries between blood and tissue. Such features can be used to extract morphological and functional information such as volumes and volume changes over the cardiac cycle. We have developed image segmentation tools for the left atrium (LA), that can be applied to 3D ultrasound images of the LA acquired throughout the cardiac cycle. Our method is able to reliably detect and track the boundaries of the atrium, allowing not only its easy visualization in 3D, but also to derive relevant LA functional indices. The method is also capable of quantifying the coupling between the left atrium and the left ventricle.

Automatic view stabilization
Cardiac interventions in the catheterization laboratory (cath lab) are often guided by a combination of x-ray and Trans-Esophageal Echocardiograpy (TEE). The TEE probe is usually controlled by another person than the interventionalist who is manipulating the catheters. Rotation and translation of the TEE probe will alter the displayed ultrasound image and can often be confusing to the interventionalist. We have developed a stabilization method that helps to visualize consistent TEE views without the need to repeatably maneuver the probe to the exact same position and orientation.

Catheter visualization
Real time image guidance during catheter based procedures is mainly done using x-ray fluoroscopy due to its ability to image intra-procedural tools (like catheters and guide wires). The drawbacks are repeated contrast injection (to view anatomic context in real time), radiation exposure and lack of depth information. We found that real time catheter tracking has the potential to visualize anatomy and the intra-procedural tools simultaneously, during interventional procedures. We have developed a method using raw ultrasound data that can differentiate the tools from tissue and detect both the position and orientation of the tools. The method has been validated in both 2D and 3D.

Treatment Monitoring
Thermal ablation can be an effective treatment for arrhythmic disorders. We have assessed the feasibility of a method based on the evaluation of a time-shift in the echo signal, and a simulation pipeline was set up. Phantoms were simulated that incorporated areas with higher speed of sound, to mimic the presence of zones of a different temperature. The time-shift caused by the “heated” zone was then evaluated. The detectability of changes in the echo signals due to temperature was found to be low, in particular for small ultrasound probes such as intra cardiac probes.

Final results and impact
The project have resulted in a set of new ultrasound based methods that together enable a comprehensive tool box which will lead to significant improvements for the treatment of patients with cardiac arrhythmias. With these methods, ultrasound has the potential to not only replace x-ray as the main imaging modality, but also to provide new insight that will increase the success rate of image guided cardiac interventions.

The knowledge that was produced in USART will lead to new ultrasound products, tailored to the needs of the electro-physiology catheterization laboratory, but also with applications in structural heart interventions as well as regular diagnostic echocardiography. Several of the results from the USART project are now been considered for commercial exploitation.

Project partners: GE Vingmed Ultrasound (Norway) and Katholieke Universiteit Leuven (Belgium). Associate partner: Oslo University Hospital (Norway)
Web site: www.usart-project.eu
Project co-ordinator: Eigil Samset, e-mail: eigil.samset@ge.com

Contact

Eigil Samset, (Research collaborations)
Tel.: +4792831484
E-mail

Subjects

Life Sciences
Record Number: 197757 / Last updated on: 2017-05-10
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