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Processing and Visualization of Body Surface Potential Maps

According to the World Health Organization (WHO) cardiovascular disease (CVD) is number one cause of death worldwide.  A diagnosis of many CVD pathologies are assisted with a primary diagnostic tool called the 12-lead electrocardiogram (ECG). The 12-lead ECG is the most popular non-invasive diagnostic tool for assessing cardiac functionality. It employs 10 electrodes and produces 12 waveforms, also known as leads. These waveforms are examined by a clinician to assist in making a diagnosis. However, this traditional ECG system does not place electrodes on the right side of the chest or on the patient’s back. Therefore, the 12-lead ECG misses important information. Fortunately, an alternative system, namely the Body Surface Potential Map (BSPM) employs up to 219 electrodes which are placed around the entire torso. This approach has been deemed more accurate for diagnosing certain cardiac pathologies when compared to the 12-lead ECG. Nevertheless, the BSPM has yet to see routine clinical practice for a number of reasons, i.e. the lack of a common BSPM storage format, visualisation techniques, standards and clinical practicalities. In summary, this research seeks to contribute to the former, which is to develop a common BSPM storage format and to visualise BSPM information coherently.

Web based application for processing and visualising Body Surface Potential Maps

R. Bond, DD. Finlay, CD. Nugent, G. Moore, University of Ulster, Belfast, Northern Ireland, UK

The Body Surface Potential Map (BSPM) is potentially more accurate for diagnosing certain cardiac pathologies when compared to the 12-lead ECG. Nevertheless, the 12-lead ECG remains the more popular technique. A contributing factor to the lack of widespread BSPM adoption is the shortage of standard methods for storing and visualizing the BSPM. For example, storage formats such as SCP-ECG only support popular techniques such as the 12-lead ECG. Based on such observations, an XML based BSPM storage format has been developed within this study. Furthermore, this format has been intimately linked with the development of a BSPM viewer. This viewer is needed, given that current visualization approaches avail of intricate scientific tools (i.e. MATLAB, map3D) which are not readily accessible or intuitive to everyday clinicians.
This viewer is web based to facilitate visualization independent of the user’s geographical location. The online nature of the tool has enabled the creation of a comments system which can be used to assist in a collaborative diagnosis. This is useful as BSPM diagnostic criteria are not well established. The viewer was created using a lossless vector graphics tool (Adobe Flash) to maintain the quality of the ECG waveforms when they are enlarged.
This viewer has been running live for 10 months alongside a weblog which has been used to record feedback and the progress. During this period, 12 experts have evaluated the viewer and influenced its development. It has been the general consensus from all experts that this is an effective solution for visualizing BSPMs. Using the viewer, a user can upload a BSPM file and view the ECG leads over their associated electrode positions on a torso. When a user selects a lead, it is displayed on a large graph. Using the tools within the viewer (i.e. calipers, isopotential maps) the user can further explore the BSPM. Algorithms have also been integrated within the system to extract and display the 12-lead ECG and the VCG from the BSPM.
This viewer has been tested to visualize two different BSPMs using a PC (3GHz CPU, 3GB RAM, 6MB broadband). The Lux-192 BSPM and the Kornreich-117 BSPM where both uploaded and visualised within 3.8 seconds (mean time from 10 trials).
This BSPM XML format and its associated viewer provide a framework for a BSPM management system. If this system is made widely available, it has the potential to provide BSPM interoperability, knowledge sharing and standardization. This has the potential to streamline the process of BSPM integration into routine clinical practice.

why, how, what and so what?

This is what he said:

http://www.raymondbond.com/bspm/demos/1/Untitled.html

Storing, visualizing and interacting with advanced Electrocardiograms

Raymond Bond, PhD Student

Email: bond-r@email.ulster.ac.uk

Supervisors: Dr Dewar Finlay, Prof Chris Nugent, Dr George Moore

Computer Science Research Institute and School of Computing and Mathematics, University of Ulster at Jordanstown

According to the Irish Heart Foundation, 10,000 people die from some form of cardiovascular disease every year in Ireland [1]. This is one reason why diagnostic cardiology has remained and should remain an important topic in research.

One of the most widely used tools in cardiac diagnosis is the 12-lead ECG. Although the 12-lead ECG is the most popular ECG acquisition method, an advanced method called the Body Surface Potential Map (BSPM) has been deemed more accurate for diagnosing cardiac pathologies [2]. Unfortunately, this technique has not seen widespread clinical use for a number of reasons. One particular reason is that standards for acquiring, storing and visualizing BSPMs are not well defined [3]. This research program will entail the development of a BSPM management system that will address these issues.

The first step in creating a BSPM management system will be to create a format to store BSPM recordings. The format will use the eXtensibe Markup Language (XML) to promote interoperability [4]. This will be the first format of its kind, as currently no format exists for storing BSPMs. The format will be innovative, in that, it will support all possible forms of BSPM multi-electrode configurations [3]. Alongside this format, a web based BSPM viewer will also be developed. This will allow clinicians to visualize and explore BSPM recordings that have been stored using the XML based BSPM format. A number of interactive tools will be included with the BSPM viewer which will enable clinicians to analyze the BSPM and make a diagnosis. In summary, this format and its associated viewer will provide a framework for a complete BSPM management system or a BSPM warehouse. If such a system is made widely available it has the potential to provide BSPM interoperability, knowledge sharing and standardization, hence putting the BSPM in widespread clinical practice.

The HISI funding will be used to support participation in the 35th conference of the International Society for Computerised Electrocardiology, which will be held in Albuquerque, New Mexico on the 21th-25th April 2010 [5]. This is the premier event for this research area and participation will allow me to disseminate my research to experts, who will provide important feedback, along with the potential to establish relationships for future collaborative research. This funding will also support me as a visiting scholar to at least one international institution that has the same research interests. Links have already been established with possible host institutions, which include the Erasmus Medical Centre in Rotterdam and the Scientific Computing and Imaging Institute at the University of Utah in Salt Lake City.

This research will clarify the benefits of BSPMs and provide some practical tools for more productive BSPM research in Ireland. BSPM research is already well established in Ireland [6] and the above activities will increase the impact of this research. With such theoretical acceptance, this practical research will help bring BSPMs to a reality in Ireland.

References

[1] Irish Heart Foundation. (2009, 16/09/09). Facts on heart disease and stroke. 2009(16/09/09), Available: http://www.irishheart.ie/iopen24/facts-heart-disease-stroke-t-7_18.html

[2] M. P. Donnelly, D. D. Finlay, C. D. Nugent and N. D. Black, “Lead selection: old and new methods for locating the most electrocardiogram information,” Journal of Electrocardiology, vol. 41, pp. 257-263, May. 2008.

[3] R. Hoekema, G. J. H. Uijen and A. van Oosterom, “On selecting a body surface mapping procedure,” Journal of Electrocardiology, vol. 32, pp. 93-101, April. 1999.

[4] S. Sfakianakis, C. E. Chronaki, F. Chiarugi, F. Conforti and D. G. Katehakis, “Reflections on the role of open source in health information system interoperability,” Yearb. Med. Inform., pp. 50-60, 2007.

[5] ISCE. (2009, 14/09/09). ISCE – international society for computerized electrocardiology. 2009(14/09/09), Available: http://www.isce.org/

[6] S. J. Maynard, I. B. A. Menown, G. Manoharan, J. Allen, J. McC Anderson and A. A. J. Adgey, “Body surface mapping improves early diagnosis of acute myocardial infarction in patients with chest pain and left bundle branch block,” Br. Med. J., vol. 89, pp. 998-1002, 2003.

http://www.primeecg.uk.com/prod_access.html

BSPMs are quantitative datasets and Bertin (1983) in his book semiology of graphics said that quantitative data can only be best visualised in position, size and different grey values. An idea would be to visualise this data using all three of these methods.

He also defines visualization:
- sender encodes informations into signs
- receiver decodes information from the signs