PDA

View Full Version : Summary of responses-electrogoniometers



Sharon Walt
11-04-1994, 12:53 AM
Dear Biomech-l'ers:

My apologies for being so tardy with this summary. Thank you to all who
responded to my request for information on the Polhemus 3-space and
electro-goniometers in general. A summary of editted responses follows.

Sharon Walt
Biomechanics Lab fax: (02)313-6190
Dept. Safety Science tel: (02)385-5413
University of New South Wales
Sydney, NSW 2052
Australia
================================================== =======================

You may consider using flexible goniometers for measuring trunk movements. As
these goniometers measure motion in two dimensions (flexion/extension and
medio/lateral movements), they may be particularly suitable for what you
want. These goniometers are commercially available from Penny and Giles,
Blackwood, UK with a portable data collection system. I have a couple of
references that may be helpful.

Rowe P, Nicol AC, Kelly IG. Flexible goniometer computer system for the
assessment of hip function. Clinical Biomechanics, 1989; Vol.4: 68-72.

James PJ, Nicol AC, Hamblen DL. A comparison of gait symmetry and hip
movements in the assessment of patients with monarticular hip arthritis.
clinical Biomechanics, 1994, Vol.9, 162-166.

Best wishes.

Rezaul Begg
Biomechanics Unit
Victoria University of Technology
Melbourne, Australia
================================================== ========================
Our lab uses the 3Space electromagnetic tracking system to measure carpal
bone motion. The tracking system is consists of a source which emits a low
frequency electromagnetic field, and 4 sensors that disturb the
electromagnetic field. A built-in CPU quantifies this disturbance in terms
of the sensors' position and orientation with respect to the source. it
needs no calibration and has an easy serial port interface; the company,
polhemus, is located in vermont. the number is 802-655-3159. let me know if
you need more info.

Tom Daniel
Allegheny-Singer Research Institute
Pittsburgh, Pa 15215
================================================== ========================
The Chatanooga Corp. produces a lumbar motion monitor that we developed at the
Ohio State University. It measures trunk motion in all 3 planes of the body.
The accompanied software also calculates the range of motion, velocity, and
acceleration.

They have a 800 number : 1-800-322-7343.
--

-------------------------------------------
Chi-Chang (Michael) Lee
The Ohio State University
Industrial & Systems Engineering
Biodynamics Laboratory
phone : (614) 292-2016
e-mail: chilee@magnus.acs.ohio-state.edu
================================================== ========================
from Elsie Culham, Queen's University:

We have used the 3 Space Tracker for measurement of sagittal plane lumbar
motion in a study of lumbar-pelvic rhythm. (Accepted for publicaton in
Spine but I'm not sure of date). Adams and Dolan in GB have used the Tracker
quite extensively for measurement of lumbar spine motion and have found it to b
e reliable and valid providing steps are taken to minimize motion between the s
ensors and skin. See Adams MA and Dolan P (1991) A technique for quantifying th
e bending moment on the lumbar spine in vivo. Journal of Biomechanics, 24:117-1
26. I know they have continued work in this area and may have some more recent
publications. Hope this information is helpful.

================================================== ========================
I have used the 3-space at the University of Waterloo, with Stu McGill, and
the Department of Physiotherapy at The University of Queensland has a later
version. It is very good hardware but the appropriate software needs to be
developed. There is also a Lumbar Motion Monitor developed by Bill Marras'
Lab at Ohio State and manufactured by Chattanooga. Bill Marras will be the
keynote speaker at the Ergonomics Society of Australia conference to be held
in Sydney in early December.
Best of luck.
Vaughan

Dr V.Kippers
Department of Anatomical Sciences
The University of Queensland 4072

V.Kippers@mailbox.uq.oz.au
Voice Mail 07 3652704
FAX 07 3651299
================================================== ========================
Three Dimensional Morphometrics: Data Capture
David Dean
Department of Cell Biology
New York University Medical Center
550 First Avenue
New York, NY 10016-6402 U.S.A.
E-mail: dean@nyu.edu

Electromagnetic Devices

Figure 1. Polhemus 3DRAW: an magnetic source underneath the digitizing
platform is detected by coils in the stylus. The three dimensional position of
the stylus tip is reported through a serial port to, most probably, a portable
computer. An entire system, including portable computer, can be
assembled that weighs less than 20Kg.
1.1 3DRAW ($6500)
Polhemus
One Hercules Drive, P.O. Box 560
Colchester, VT 05446
tel (802) 655-3159
fax (801) 655-1439

This fourth generation device has been used by
several investigators to study non-human primate and
human crania (see Dean, this volume; Lele and
Richtsmeier, 1992; Corner et al., 1992; Richtsmeier and
Walker, 1993; Vannier and Conroy, 1989). Originally
developped to be mounted on a fighter pilot helmet to
track head movements (Raab et al., 1979), this
application was soon obsoleted by laser-based sighting
devices. It consists of a platform under which a fixed 3
axis magnetic source is emitted. A specimen can be fixed
to the surface of this platform. This object is digitized
with the aid of a hand-held stylus.
The stylus is equipped with a 3 axis magnetic sensor
that allows a small computer to determine the location of
the tip in 3 space, including xyz normal information.
Because it assumes the magnetic field is constant, the
work area should be kept reasonably clear of ferrous
objects. None should be within a meter of the digitizing
envelope, and other large iron objects such as steam
heated radiators and filing cabinets should be 2-3 meters
away. Given a changing ferrous environment, the device
should be recalibrated (it comes with calibration
software) before each digitizing session. Unless the
stylus is used very carefully, the normal information is
not very important as part of the morphometric data
collected. However, the viewpoint of the data collection
interface can be tied to the stylus. This allows easy
perusal of the data from various points of view, a
crucial error-checking step whenever potentially
overlapping coordinates are collected.
Their is firmware control of the stylus data report;
it can be set in point or continous mode on the fly.
Continuous mode is very useful for tracing edge features
(see Dean, this volume). The accuracy of this device has
been tested internally by Polhemus using widely accepted
methods (Krieg et al., 1992) and has shown accuracy of
0.01" RMS (Root-Mean-Square), or 0.254 mm. While this is
more than a two-fold improvement over the original (first
generation) 3SPACE device, the generation of the device
that has commonly been used with large non-human primate
and human skull material, it is still below the
acceptable range for most dental studies.
The latest version of this device is highly
portable. The 3DRAW table, stylus, and data handling
device all together weigh less than 12 pounds. There is a
padded, hard-shell, airline check-in carrying case
available.
An interface was recently released that allows the
data collected by this device to be sent to the CADKEYS
generic CAD program. This flexible PC program can be
readily tailored to most biometric applications. It is
included, gratis, with the device. Another longstanding
interface for Polhemus, Metrecom, Scientific Accessories
(see the latter two below) devices is marketed by Mira
Imaging (2257 South East, Suite 1A, Salt Lake City, UT
84106, tel. 801/466-4641, fax. 801/466-4699). This
interface, HyperspaceTM, is primarily aimed at producing a
surface mesh of solid objects. The NATO morphometrics
workshop attendees tested this software and found it
difficult, but not impossible, to adapt to morphometric
applications such as single point or space curve
digitization.

1.2 DigiTracker (est.