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  • summary of replies (method to simulate the effect of the skinartifact on the marker position)

    BIOMCH-L@NIC.SURFNET.NL



    The replies I have got regarding modeling skin artifacts.

    The original question is at the bottom.

    Thank you all

    Raziel









    Dear Raziel Riemer, the issue you raise is in fact very important, and I
    agree that what has been exploited so far is somewhat inadeguade to
    represent with realism the terrible skin motion artefact effect. Definitely
    a standard hasn't been established. A general introduction to this and
    related topics can be found also in our recent review in G&P, as below.

    In particular, in addition to what you report, I point out to you the
    several papers from Andriacchi's group [ref 42-44 in the review], recently
    discussed in a study from this group [45], the papers from Cerveri and
    Pedotti (which have progressed since then, see in PubMed), which seem to
    have utilised forms of SMA as well, and also the following, which perhaps is
    the most recent and complete measure of this artefact. Do not hesitate to
    ask for additional info. All the best for your study.



    Stagni R, Fantozzi S, Cappello A, Leardini A.

    Quantification of soft tissue artefact in motion analysis by combining 3D
    fluoroscopy and stereophotogrammetry: a study on two subjects.

    Clin Biomech (Bristol, Avon). 2005 Mar;20(3):320-9



    Leardini A, Chiari L, Della Croce U, Cappozzo A.

    Human movement analysis using stereophotogrammetry. Part 3. Soft tissue
    artifact assessment and compensation.

    Gait Posture. 2005 Feb;21(2):212-25. Review



    ************************************************** ***********************

    Alberto Leardini, DPhil

    Movement Analysis Laboratory

    Centro di Ricerca Codivilla-Putti

    Istituti Ortopedici Rizzoli

    Via di Barbiano 1/10, 40136 Bologna ITALY

    tel: +39 051 6366522

    fax: +39 051 6366561

    email: leardini@ior.it

    http://www.ior.it/movlab/



    "Where is the Life we have lost in living, Where is the wisdom we have lost
    in knowledge, Where is the knowledge we have lost in information."

    Thomas Stearns Eliot, Choruses from ''The Rock'' (1934)









    I remember a presentation by Dr. Albert King of the Wayne State University
    Bioengineering Center. In that presentation, he used high-speed xray to
    examine knee joint kinematics during run and jump activities. If I recall
    is words during the talk correctly, he compared the internal bone kinematics
    with external skin deflections, and saw large differences. You might want
    to do a literature searh on Dr. King's work, or contact him directly. Hope
    this helps.



    - Matt







    Matthew R. Maltese, M.S.

    Biomechanical Research Engineer

    TraumaLink

    The Children's Hospital of Philadelphia

    267-426-7025 voice

    215-590-5425 fax

    maltese@email.chop.edu



    US Postal Service Mailing address:



    The Children's Hospital of Philadelphia

    34th & Civic Center Boulevard

    3535 TraumaLink, 10th Floor

    Philadelphia, PA 19104







    Dear Raziel,



    whereas our concern was more to get a smoth motion of our model than

    actually to simulate skin artifacts we used spring damping elements to

    attach the markers to the model with very satisfactory results.

    The spring constants were set to k= 10^6 N/m and the damping constant to

    b=10^4 Ns/m



    You can find a description of the model in:

    Arampatzis et al.

    A three-dimensional shank-foot model to determine the foot motion during

    landings.

    Med Sci Sports Exerc. 2002 Jan;34(1):130-8.



    Hope this helps.



    Sincerely,



    Gaspar Morey





    ----- Original Message -----

    From: "Raziel Riemer University of Illinois at"

    To:

    Sent: Thursday, October 06, 2005 5:02 AM

    Subject: [BIOMCH-L] method to simulate the effect of the skin artifact on
    the marker position





    Dear biomch-l members,



    I am looking for a method to simulate the effect of the skin

    artifact on the marker position.



    The references that I have found (e.g., Che`ze et al.,

    1995; Lu and O’Connor, 1999; Roux et al., 2002) used A sin

    (w*t+Q) formulation to simulate skin movement artifacts,

    where A is the amplitude of the noise, w is the frequency, t

    is the simulated time, and Q is the phase angle. For a

    given trial, the values of A, w and Q for each marker were

    taken randomly to lie between zero and a set upper limit.



    My question is whether this the standard way, or are there

    different methods to simulated this effect?>

    Thank you very much for your help!

    Raziel





    Reference

    Chéze, L., Fregly, B.J., and Dimnet, J., 1995. A

    solidification procedure to facilitate kinematic analyses

    based on video system data. Journal of Biomechanics 28, pp.

    879–884



    Lu, T. W. and O’Connor, J.J., 1999. Bone position estimation

    from skin marker coordinates using global optimisation with

    joint constraints. Journal of Biomechanics 32, pp. 129–134



    Roux, E., Bouilland, S., Godillon-Maquinghen, A.P., and

    Bouttens, D., 2002. Evaluation of the global optimisation

    method within the upper limb kinematics analysis. Journal of

    Biomechanics 35, pp. 1279–1283.


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