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Hi Alban,

I've spoken with some people here about this -- I've inserted their responses below...

From Rob MacLeod:

The justification I know of actually comes from the electrocardiography literature in which the ECG one records from the wrists is the same as that from the shoulders. There is an ECG system called the Mason-Likar that places the classic "limb leads", i.e., the electrodes on the hands and feet, at surrogate locations on the front of the shoulders and the lower torso, just above the pelvis. The original purpose of this system was to make it more convenient with patients--moving them around or working on parts of their torso is simpler when there are not these long wires handing from their wrists and ankles. But the consequences for forward simulations are that one can ignore the arms and the lower part of the body when computing the ECG from a known source.

The reference for this is:

@Article{RSM:Mas66,
  author =       "R.E. Mason and I. Likar",
  title =        "A New System of Multiple-lead Exercise
                 Electrocardiography",
  journal =      "American Heart J",
  year =         "1966",
  volume =       "71",
  month =        feb,
  pages =        "196--205",
}

Another way to look at it is that the potential gradients (and amplitudes for that matter) are very small at the lower torso when we measure them in the electrolytic torso tank.

And from Frank Sachae:

Hi Alban,

you can find a proceedings paper at

http://www-ibt.etec.uni-karlsruhe.de/postscript/cic98fs.ps

which addressed the spatial region problem. The paper gives some numbers on
the influence of the region selection to calculated BSPMs.

The reference for the paper is:

F. B. Sachse, C. D. Werner, K. Meyer-Waarden, and O. Dössel. Solving the
forward problem in electrocardiograpy: Analysing the selection of regions of
impedance models. In Proc. Computers in Cardiology, volume 25, pages
701–704, 1998.

And to answer your second question, we use no-flux Neumann boundary conditions because the air surrounding the body acts as an insulator.

Cheers,
Dave



On Jun 3, 2004, at 10:28 AM, Alban Pagès wrote:

Good evening,

I have a few questions about resolution of forward problem of
electrocardiographie.
1) When you calculated the forward probleme of electrocardiography, you used
only a thorax model. Why don't you take a total body? Do you have any
publication to justify this reduction? Which bondary condition do you use on
cut surface and why?
2) It seems that you used Neuman bondary condition on the thorax. Is it
right and why?

Thank you for your time and your help,
Best regards,
Alban

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• [SCIRUN-USERS] Contour Plots in SCIRun, Eduardo Morales, 06/03/2004
  • [SCIRUN-USERS] Thorax, Alban Pagès, 06/03/2004
    • Re: [SCIRUN-USERS] Thorax, David Weinstein, 06/03/2004
  • Re: [SCIRUN-USERS] Contour Plots in SCIRun, Michael Callahan, 06/03/2004

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