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Raziel Riemer
10-26-2005, 02:05 PM
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.