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Pat Fanning
01-23-1995, 10:19 PM
Dear Netters,

A long time ago I posted the following two questions. I'm sorry
about the delay in posting my summary of responses. I'd like to
take this chance to thank everyone who helped me with these
problems.

thanks again
Pat Fanning

----------------------

>Dear Netters,
>
>A friend is using Fuji prescale pressure measuring film to measure to
>pressure in bone joints. The film he is using is designed to measure
>Super Low pressure, in the range of 5 to 25 kgf/cm2. The film changes
>colour in accordance to the amount of pressure applied to it. I have
>two questions about this product.
>
>1) Does anyone know how to convert kgf/cm2 to Pascals?
>
>2) Has anyone any experience in translating these or similar patterns
> into pressure data? We have access to a colour scanner, so does
> anyone know of any programs that can divide a colour image into
> regions of similar colour?
>
>Thanks in advance for any help you can provide. As usual I will provide
>a summary of answers received.
>
> Pat Fanning

----------------------

The answer to the first question is fairly obvious.

1 kgf = 1 * g N =~ 9.81 N

=> 1 kgf/cm2 = 10000kgf/m2 = 98100 N/m2 = 98.1 kPa.

Thanks to all those who replied to this question. They were

Hans Vos (j.e.vos@med.rug.nl)
Dieter Rosenbaum (diro@sirius.medizin.uni-ulm.de)
Graham Robinson (mecgcr@clust.heriot-watt.ac.uk)
Dan Levine (dll@zim.bms.com)
Jesus Dapena (dapena@valeri.hper.indiana.edu)
Brian W. Bergemann (BWBERGEMANN@ussa-admin.ussa.edu)
Eric Powell (epowell@fs1.ho.man.ac.uk)
Joseph Hale (jeh7a@galen.med.virginia.edu)
Carlos Melendez (carlos@pliers.unm.edu)
Christian Haid (Christian.Haid@uibk.ac.at)
Thomas G. Loebig (tom@biomechanics.asri.edu)
Christopher Allen Favre (Favre@aol.com)
Mike=Gross%PT%MAH@css.unc.edu
Orit YARDEN (yarden@eng.tau.ac.il)
Phil Morrison (PHILM@tekotago.ac.nz)
Peter M. Quesada (peter@gait1.gait.ohio-state.edu)
Moshe Nissan (nissanm@techunix.technion.ac.il)
Charles Luevano (chuck@slider.unm.edu)
E. C. "Ned" Frederick (72735.77@compuserve.com)

----------------------

The following is a list of replies to the second question.

----------------------

From: diro@sirius.medizin.uni-ulm.de (Dieter Rosenbaum)

Pat:

2. We have been using a digital image analysis system which -after calibration-
provided the information on contact area, average and peak pressure (for
measurements of the Chopart joint loading before/after calcaneal fractures).
The product of contact area and average pressure will give you an estimate
of the transitted force. I don`t know how to use the scanner for that
application but it will probably depend mostly on the capabilities of the
software you are using and the resolution of the scanner.

I hope this helped, feel free to contact me if you have additional questions.
Ciao,

Dieter...

************************************************** *****************************
* Dr. Dieter Rosenbaum voice:(0)731 - 502 3492 *
* Abteilung Unfallchirurgische fax: (0)731 - 502 3498 *
* Forschung und Biomechanik email: diro@sirius.medizin.uni-ulm.de *
* Universitaet Ulm *
* Helmholtzstr. 14 *
* 89081 ULM *
* Germany *
************************************************** *****************************

----------------------

From: "Joseph E. Hale"

>
>2) Has anyone any experience in translating these or similar patterns
> into pressure data? We have access to a colour scanner, so does
> anyone know of any programs that can divide a colour image into
> regions of similar colour?
>

I have do a fair amount of work with Pressensor film, both in terms of
characterization its behavior and application to joint contact stress
measurement. As a starting point, you make want to look at the following
papers:

Singerman, RJ, Pedersen, DR and Brown TD: Quantitation of Pressure
Sensitive Film Using Digital Image Scanning. Experimental Mechanics
27:99-105, 1987.

Hale, JE and Brown, TD: Contact Stress Gradient Detection Limits of
Pressensor Film. Journal of Biomechanical Engineering 114:352-357, 1992.

Most image analysis software packages will allow you to look at image
intensity (which can be correlated to applied pressure) for individual
pixels within the region of interest. We used a commercial package from
Precision Visuals (PV-Wave) on a DEC workstation. Another option for the
Macintosh is a package called Image, which is available free through the NIH.

I hope this information is helpful. Please feel free to contact me directly
if you have additional questions.

Joe Hale

Director, Orthopaedic Biomechanics Laboratory Tel: 804-924-5989
University of Virginia FAX: 804-924-1691
Charlottesville, VA USA email: jhale@virginia.edu

----------------------

From: "J.B. FINLAY"

Dear Pat:

In quantifying your Fuji-film stains, you may wish to refer to
the following papers which address the applications and technical
limitations of this material.

In particular, you should be wary of assigning a "meaningless"
number of Pressure Ranges to your images. The Pressure Ranges
should be established with respect to the standard deviations
achieved when Calibration Stains are produced at nominal
pressures. The number of "valid" Pressure Ranges with such a
quantitative approach may be small; however, "image averaging"
(using several images) can improve the resolution and increase
the number of meaningful ranges.

Liggins, A.B. and Finlay, J.B. Recording contact areas and
pressures in joint interfaces. In Experimental Mechanics (Ed E.
G. Little), 1992, pp. 71-88 (Elsevier Science Publishers,
Amsterdam).

Liggins, A.B., Stranart, J.C.E., Finlay, J.B. and Rorabeck,
C.H. Calibration and manipulation of data from Fuji
pressure-sensitive film. In Experimental Mechanics (Ed E. G.
Little), 1992, pp. 61-70 (Elsevier Science Publishers,
Amsterdam).

Liggins, A.B. and Finlay, J.B. Sterilization of Fuji pressure-
sensitive film. Medical Engineering & Physics 16(?): In Press,
May 1994.

Liggins, A.B., Hardie, W.R. and Finlay, J.B. The spatial and
pressure resolution of Fuji pressure-sensitive film.
Experimental Mechanics, In Press, November 1994.

Liggins, A.B. and Finlay, J.B. Image-addition provides enhanced
resolution in analyses with Fuji pressure-sensitive film.
Experimental Mechanics, 1994, Submitted.

Liggins, A.B., Surry, K. and Finlay, J.B. Sealing Fuji
Prescale pressure-sensitive film for protection against fluid
damage: The effect on its response". Strain: Submitted, July
1994.


For further information or reprints of these papers, you should
contact my colleague
Adrian Liggins, PhD at:

519-663-3843 Phone
519-663-3904 FAX

Liggins@ortholab.uh.rri.uwo.ca

His e-mail is currently out-of-service, so any e-mail to him can
be directed through my account.

Best wishes:

Bryan Finlay, PhD 519-663-3063
Director of Orthopaedic Research 519-663-3904 FAX
University Hospital
P.O. Box 5339
London, Ontario, CANADA, N6A 5A5

----------------------

From: "Thomas G. Loebig"

My colleagues here have considerable experience with Fuji and will no doubt
reply to you next week as they are out of town until Monday. If you haven't
heard from Don Anderson or Tom Daniel soon, write back and I'll tell them of
your query.

Good Luck

Tom

Thomas G. Loebig, MSME Research Associate
Allegheny-Singer Research Institute tom@biomechanics.asri.edu
320 E. North Avenue,10th Floor ST voice: (412)359-6773
Pittsburgh, PA 15212-4772 fax: (412)359-3494

----------------------

From: Favre@aol.com

Pat,
As far as analysis of the pressure data. I have had some experience
with data similar to this; however it was topographic. The principle though
is still the same. I would enter this data in as a matrix. This would give
the pressure data on a 2D plane. With this data you could enter it into a
program like Mathematica, MathCAD, or even the HP48's to get a contour or
surface plot. Mathematica is really the best when it comes to the surface
plots. The surface plot will give you a 3D rendering of your data. You must
note though that this plot is dependant upon how the film was placed. For
example, if the film was flat and a force was placed upon it, the x,y axis
would be rectangular. If it was placed around a spherical surface, for
example a ball and socket joint, you must take into account the curvature.
Simple vector calculus can yield how the grid lines must then be drawn. I
have a program in FORTRAN and C++ which can analyze the data and come up with
the peaks, and their location. This is only good though for flat surfaces.
When it comes to simplifing the data, I have used Harvard Graphics Plus.
It has a mechanism that can read adjacent colors, and simplify them. This
is similar to what happens on TV when they hide a person's face. The main
problem that I have encountered though is with the scanner. If you use an
inferior scanner, it may read and put colors that are not really there, and
thus distort the scanned image.
I hope that these ideas will help your friend. If you would like a copy
of the peak program, just write me.

-Christopher Allen Favre
Sophmore, Misssissippi Gulf Coast Community College

----------------------

From: PHILM@tekotago.ac.nz

Pat, I have had similar problems with analysis of thermographic images. The
most basic solution is relatively easy in principle since you only have to
be count each pixel of the scanned data. Unfortunately I have only found
very expensive options to the dilemma and time pressure prevents me from
writing the software myself.

The one of the cheapest options so far has been image processing tools
developed for the package LabView. It runs on the Mac/IBM/Sun and the tools
were developed by a French firm who's address I cannot lay my hands on
at the moment (cost US$1200 to 3200). However the US address is
GTFS Inc., 2455 Bennett Rd, #100C, Santa Rosa, CA95404

Two other sources were
Image Analyst by Automatix, 755 Middlesex Turnpike, Billerica, MA US$2000
(again a little too sophisticated for my purposes)
Enhance v2.x by Microfrontier, 7650 Hickman Rds, Des Moines, IA50322. (US$375)
Note both only run on the Macintosh

I would appreciate if you come across any other solutions. This problem is on
a back burner for me at the moment.
My immediate solution is to visit either the Pathology/ Anatomy/ Physiology
departments and use theirs. A case of a sledge hammer to crack a nut.

Best of luck

Phil Morrison
New Zealand

----------------------

From: hound-dog

as far as using your color scanner, i think you might be able to to it.
what you would have to do is to calibrate it. if you could apply known
pressures, for instance with a materials testing machine, you could scan
those in and use for references as your calibration.

from the work with what i have done with the same film, i do believe it
works by popping more bubbles (with the developer for the film) at
higher pressures. if you do a close up on a low pressure region and
count the corpuscles which have popped and developed, i think you will
find them less per unit area than for a larger pressure

hope this is of help.

************************************************** ******************************
Matt Rupert rupertmp@ucunix.san.uc.edu
Department of Aerospace Engineering
and Engineering Mechanics
University of Cincinnati, Ohio
************************************************** ******************************

----------------------

From: Matt

Prof. Roger Haut of Michigan State University (East Lansing, Michigan, USA)
has used Prescale film in measurements of cartilage loading during patella
impact in rabbits. Try the following email address:

haut@msm.msu.edu

or call US phone number: 517-355-0320

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

Matthew Reed
Senior Research Associate
University of Michigan
Transportation Research Institute
matt@biosci.umtri.umich.edu

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

----------------------

From: "E. C. Frederick"

We have had some limited expreience with Fuji film. In our experience it is
best used as a measure of relative pressure distribution. Incidentally I
believe Fuji sells a scanner with analysis software to convert the various
colors to pressures.

In my experience 5 to 10 kgf/cm^2 pressure is not all that low for a
biomechanical system. Plantar pressures, in walking for example, can peak in
that range.

__________________________________________________ __________________________
E. C."Ned" Frederick, Ph.D. Phone: 603.772.2505
Exeter Research, Inc. Fax: 603.772.5463
8 Chestnut Street
Exeter, NH 03833-1859 USA EMail: 72735.77@Compuserve.com
__________________________________________________ ___________________________

----------------------

From: dll@pendragon.zim.bms.com (Dan Levine)

Hello Pat:

Re question 2) above: Our Tribology group does not utilize tools which
distinguish colour variations in Fuji images. They use some simple technique
to measure the overall area only.

Dan Levine
Zimmer, Inc. / Warsaw, Indiana, USA
dll@pendragon.zim.bms.com

Pat Fanning | "I don't know half of you half as well
pfanne92@irlearn.ucd.ie | as I should like; and I like less than
| half of you half as well as you deserve."
Dept. Elec. Eng. |
University College Dublin | - Bilbo Baggins
Belfield, Dublin 4 | The Fellowship of The Ring,
Ireland | J. R. R. Tolkien