View Full Version : Summary: porous indenter

Brian Davis
09-19-1996, 09:39 AM
I recently requested information about porous indentors that could be
used to compress cartilage while it was being imaged in an MRI machine.
The response I received was excellent--in fact an unexpected bonus of
posting this request was that someone actually delivered
three samples of porous aluminum RIGHT TO MY OFFICE!

This has prompted me to ask if anyone knows of a SGI computer that
can be used in the vicinity of a MRI machine?

My office number is W1-518, and deliveries can be made at any time! :-)

The suggestions I received included contacting Drs Joe Mansour (Case
Western Reserve University, Jian Yao (University of Leeds), Prof Mow
(Columbia University) and Neil Broome, who was last in Auckland
University, New Zealand.

In addition, it was suggested that thick-walled honeycomb materials or any
stiff columns with longitudinal holes in them might work. Other ideas

The porous indentor that we use in our cartilage indentation studies is
sintered metal -- probably not what you want for studies inside an MRI
magnetic field. When I was doing my graduate work at Iowa, we tried using
a porous ceramic material that was borrowed from an aquarium pump. However,
we eventually ended up using a nonporous indentor due to problems machining
the brittle ceramic material.

Joseph E. Hale, Ph.D.
Orthopaedic Biomechanics Lab., Box 374 TEL: 804-924-5989
University of Virginia FAX: 804-924-1691
Charlottesville, VA 22908 USA email: jhale@virginia.edu

I guess it would depend on how porous you want, and what effect you
are measuring. You could, for example, use a solid indenter and "wick"
the water, (or aqueous matter) out with a layer of filter paper inbetween
cartilage and indentor.

Brian Ziegelaar Phone: +61 9 346 1530
Lions Eye Institute Fax: +61 9 382 1171
Centre for Ophthalmology and Visual Science
Nedlands, Western Australia

A colleague forwarded your note to me. You might want to get in touch
with Hoechst (they make polymers). I was looking for porous ultrahigh
molecular weight polyethylene for a different reason, but never got
around to following up. The telephone number I was given was Louie Wang,
Hoechst Celanese Corp., 1-800-242-UHMW. UHMWPE has a modulus of about
500MPa, so it might work.

Stephen Ferguson
Queen's University


A good material to try is a reticulated foam of alumina. This ceramic is
very commonly available and is used for filtering molten metals, so is
easily available and comes in a variety of different pore sizes. The
alumina will give it strength and also because of the morphology, the
pores are interconected and thus the water should move freely. Should be
OK for MRI.

Jonathan Knowles
Dept. of Biomaterials,
Eastman Dental Institute,
256 Gray's Inn Road,
London WC1X 8LD

Brian, try synthered pyrex glass. They come in discs of different
diameters and various pore sizes.
Regards, Joe

Prof. Joseph Mizrahi , D.Sc.
Dept. of Biomedical Eng. Technion, Israel Institute of Technology
Haifa 32000, Israel
Phone: +972-4-829 4128 Fax: +972-4-823 4131
e-mail: jm@biomed.technion.ac.il

================================================== =============

Many thanks to Dajun Zhang, Alan Litsky, Gail Perusek, Stephen Ferguson,
Jonathan Knowles, Joe Mizrahi, Brian Ziegelaar, Mark Swanepoel, and
Jian Yao.
Name: Brian L. Davis, PhD
E-mail: davis@bme.ri.ccf.org
Date: 09/17/96
Time: 17:08:34