View Full Version : Biomch-l 6/1989

Herman J. Woltring
03-14-1989, 01:50 AM
Today's topics:

(1) ISB-XI Proceedings available
(2) Proceedings Biostereometrics '88
(3) Book received for review: 'Neuromechanical Basis of Kinesiology'
(4) Watsmart and Optotrak
(5) Clinical Gait Analysis
(6) Call for Papers, 11th IEEE EMBS in Seattle
(7) Correction: BIOMCH-L 5/1989


(1) ISB-XI Proceedings available

A few days ago, I received the Proceedings of the 11th Congress of the Inter-
national Society of Biomechanics held in 1987 at the Free University of Amster-
dam. Geert de Groot, A. Peter Hollander, Peter A. Huijing en Gerrit Jan van
Ingen Schenau did a fine job of editing, and they can be congratulated with
their result. Regretfully, the ISB assembly decided in Amsterdam that the tra-
dition of two hard-cover proceedings volumes per congress should be discon-
tinued. The Proceedings have been published as "Biomechanics XI-A and XI-B"
by the Free University Press of Amsterdam/NL in the International Series on
Biomechanics, Vols. 7-A and 7-B; ISBN 90-6256-679-0 (set) CIP. They can be
obtained from:

VU Boekhandel/Uitgeverij bv
De Boelelaan 1105
NL-1081 HV AMSTERDAM, The Netherlands


(2) Proceedings Biostereometrics '88

Biosterometrics '88 (5th International Meeting) was organized in Basel/Swit-
zerland on 14-17 November 1988 and chaired by Prof.dr. Juerg U. Baumann (Motion
Analysis Laboratory, University of Basel and Children's Hospital Basel) and
Prof.dr. Robin A. Herron (College of Applied Human Sciences at Colorado State
University). The Proceedings are expected to be published this month as SPIE
volume 1030 (non-member price US $ 68,00). I have not yet seen them, but the
conference programme lists a variety of topics pertinent to the scope of
BIOMCH-L. Various presentations were concerned with external shape analysis,
medical imaging of internal organs and structures (CT/MRI), and with movement


(3) Book received for review: 'Neuromechanical Basis of Kinesiology'

Title: Neuromechanical Basis of Kinesiology
Author: Roger M. Enoka, PhD (University of Arizona)
Publ. date: 7 July 1988
Price: US $ 29,00
Number of pages: 352
ISBN: 0-87322-179-6 (cloth)
LoC-Number: 87-29745
Publisher: Human Kinetics Publishers, Inc., Box 5076,

A review of this nice book will be published in the near future. At this time,
I'd like to confine myself to the general statement that the book seems directed
at the undergraduate student with limited prior exposure to calculus. The book
is largely theoretical in nature, and thus does not address the practical prob-
lems of human movement analysis and simulation.


(4) Watsmart and Optotrak

Considering the previous BIOMCH-L postings on Watsmart and Optotrak, I'd like to
stress that both systems are manufactured by the same (Canadian) manufactorer.
The ISB-XI proceedings contain two papers from the University of Toronto on Wat-
smart, one of which deserves to be mentioned in the context of these postings:

Kevin A. Ball & Michael R. Pierrynowski, A Modified Direct Linear Transfor-
mation (DLT) Calibration Procedure to Improve the Accuracy of 3D Reconstruc-
tion for Large Volumes (XI-B, pp. 1045-1050).

On p. 1047, the authors state: "For use with optoelectronic data acquisition
systems such as the WATSMART (WATerloo Spatial Motion Analysis and Recording
Technique) system employed in our laboratory, an additional level of error
reducing software has been developed. Accuracy testing experimentation per-
formed in our laboratory has revealed that during dynamic trials up to 2.2%
of the 2D data collected with the WATSMART system may contain large errors.
Figure 1 provides an illustration of unsmoothed reconstructed data for the
vertical displacement of a single marker located on a swinging pendulum.
Northern Digital Inc., makers of this system, have attributed these errors to
be the result of active marker reflections. Errors of this nature have been
less apparent with static testing of the system, however, we have concluded
that some error checking procedure should be incorporated (...)".

The quoted figure shows a pseudo-sinusoidal signal with a peak-to-peak ampli-
tude of about 0.3 m, and a period duration of about 75 'frames' (presumably,
one frame lasts about 200 usec), with short 'glitches' at reproducible posi-
tions whose amplitudes range between 0.3 and 0.6 m. Presumably, these glitches
occurred when light from the active IR-LED marker on the pendulum was reflected
via a SPECULAR surface (the ground?) into the observing camera('s). By virtue
of their short duration, these glitches could be easily recognized from the data
time trace, and thus removed in s/w. In general, however, reflections may also
occur at more diffusely reflecting surfaces, so that transient glitches are less
likely to occur. I presume that such effects (which I have personally observed
with SELSPOT-I, and which may also occur with SELSPOT-II and IROS) motivated
the manufacturer to design and market Optotrak. Because of the different type
of opto-electronic sensor used in Optotrak, reflection problems should now be
avoidable (experimental data like those presented in the Ball & Pierrynowski
paper would be highly relevant at, e.g., ISB XII). The higher price of Opto-
trak as compared to Watsmart does not seem unreasonable as not only reflection
problems might now become avoidable, but as the manufacturer claims a fourfold
improvement in spatial accuracy, and a twofold improvement in temporal accuracy.
Of course, the need for wired markers on the subject's body is a disadvantage
(to be compensated perhaps by special leotards with in-sown wires to be donned
by the subject or patient), but the automatic identifiability of multiple wired
markers is a significant advantage with respect to systems utilizing non-wired
markers with possibile misidentification in software.

(One might note that high spatio-temporal resolution is required for re-
liable assesment of the derivatives needed under kinetic analysis; cf. the
studies by Lanshammar in the 1982 volume of the Journal of Biomechanics).


(5) Clinical Gait Analysis

Considering the earlier postings by Mike Whittle (Oxford/UK) and by Ton van den
Bogert (Utrecht/NL) on 'clinical gait analysis', another interesting paper in
the ISB-XI Proceedings is from workers at the University of Kingston, Ontario,

Sandra J. Olney, Patrick A. Costigan, William F. Boyce and Ian D. McBride,
Compensatory Muscle Group Work in Gait of Cerebral Palsied Children (XI-A,
pp. 389-392).

Based on planar analysis of locomotion (cf. D.A. Winter, The Biomechanics and
Motor Control of Human Gait, University of Waterloo Press, Ontario, Canada,
ISBN 0-88898-078-7, 72 pp.), the authors performed a dynamic/kinetic analysis
using net joint power at hips, knees, and ankles. They concluded that their
"(...) cerebral palsied children produced the proportion of work from their
hips that normal individuals supply from their ankle plantarflexors. They
accomplished this by a normal pull-off and an exaggerated increase of hip
extensor power at the end of swing phase and the beginning of stance phase".
Furthermore, they found certain differences between hemiplegics and diplegics.


(6) Call for Papers, 11th IEEE EMBS in Seattle

Date: Mon, 13 Mar 89 17:21:00 PST
Original sender: Radiology Special Interest Group
Forwarded from: Alan Rowberg
Subject: Call For Papers, 11th IEEE EMBS in Seattle

11th Annual International Conference
IEEE Engineering in Medicine and Biology Society
November 9 - 12, 1989

You are invitee to present a paper at the Eleventh Annual International
Conference of the IEEE Engineering in Medicine and Biology Society to be
held here in Seattle on November 9-12, 1989. The main theme of this
year's conference is "Images of the 21st Century," and there will also
be a special symposium on biomedical imaging during the conference.
This meeting has been progressively advancing in stature, and medical
imaging has started to play a very significant role. This year there
will be a track entitled "Picture Archiving and Communication Systems"
to be held across several days of the meeting. These presentations will
be during the portion of the meeting that involves simultaneous
sessions, so we will be able to accept a large number of papers, and not
suffer the restrictions that occur at many other meetings.

Naturally, there is the usually full spectrum of material presented at
other sessions during the meeting, in addition to an impressive social
program, including a cruise on Puget Sound and a salmon bake.

The deadline for complete two-page papers is May 1, 1989. Unlike
previous years, it is not necessary to prepare an abstract in advance of
that time. Please send your request for an author's kit to: CORE
COMMUNICATIONS, 2111 Wilson Boulevard, #700, Arlington, VA 22201.

I hope that you will consider presenting a paper on your work at this

Alan H. Rowberg, M.D.
Assistant Professor, Radiology
University of Washington, Seattle


(7) Correction: BIOMCH-L 5/1989

The previous biweekly BIOMCH-L posting was erroneously called BIOMCH-L 4/1989.


End of BIOMCH-L 6/1989