View Full Version : Magnetic movement trackers

Herman J. Woltring
09-13-1990, 02:39 PM
Dear Biomch-L readers,

Sometime ago, Leendert Blankevoort of Nijmegen University posted a request on
Biomch-L for details about Polhemus Inc of Colchester, VT, USA. Having acqui-
red the Polhemus "3Space Isotrack" device for 6 d.o.f. measurement of joint
and segment movement (60 or 30 Hz sampling frequency, resolution in the mm and
sub-degree ranges, US price 3 k$), I would be interested to get in touch with
other users of this system. The software provided with the 3Space system is
quite limited, and it might be useful to collaborate in developing 3-D kinema-
tics data acquisition, processing, and representation software. I have a COM-
PAQ DeskPro 386/20e (40 MB hard disk / 4 MB extended memory / VGA graphics)
with MSDOS 4.01, Microsoft Windows 3.0, and Microsoft Fortran 5.0. Some uti-
lities to be developed will be rather device-specific (data acquisition with
synchroneous buffering, some of the graphics), while others might be more
portable (rigid-body kinematics, smoothing, joint angle and instantaneous
axis/centre of rotation calculus). For the feasibility of such procedures
in a Roentgenstereophotogrammetric context, see the recent papers from the
Nijmegen group in the Journals of Biomechanical Engineering and of Orthopaedic

My interests are methodological (how well can we assess details of in-vivo
joint motion), fundamental (what kind of movements occur under various loading
conditions, e.g., when co-contractions are varied), and applied (physiotherapy:
monitoring of joint mobility improvement during and between treatment ses-

A technical note describing results with (an earlier version of) the 3Space
system was published by K.N. An, M.C. Jacobsen, L.J. Berglund, and E.Y.S. Chao
of the Mayo Clinic in Rochester, MN 55905, U.S.A.: see their article "Applic-
ation of a Magnetic Tracking Device", Journal of Biomechanics 21(1988)7, 613-

Interestingly, it would seem that Polhemus has now its first competitor only
a few metres away: Ascension Inc, also at Hercules Drive in Colchester, VT.
Those of you interested in contacting the manufacturers may find the following
information helpful:

Polhemus, Tel. +1(802)655-3159, fax +1(802)655-1439, P.O.B. 560, BURLINGTON,
VT 05446, U.S.A.

Ascension, Tel. +1(802)655-7879, fax +1(802)655-6305, P.O.B. 527, BURLINGTON,
VT 05402, U.S.A.

With kind regards,

Herman J. Woltring
CAMARC-partner (NL)
Brussellaan 29, NL-5628 TB EINDHOVEN, The Netherlands
Tel. (private) +31.40.480 869, Voice/Fax/Modem +31.40.413 744

CAMARC ("Computer Aided Movement Analysis in a Rehabilitation Context") is a
project under the Advanced Informatics in Medicine action of the Commission
of the European Communities (AIM/DG XIII-F/CEC), with academic, public-health,
industrial, and independent partners from Italy, France, U.K. and The Nether-
lands. Its scope is pre-competitive.