Perforated steel Grid material -- use stainless steel

[Beth Brainerd]

Hi XMALab Group and XROMM User Group (XUG),

The original perforated steel we selected for fluoroscope image undistortion is magnetic and can cause problems getting good distortion correction because fluoroscopic image intensifiers are highly sensitive to magnetic fields. The bad magnetic perforated steel is the McMaster Carr part number reported in our 2010 paper: Brainerd, E.L., Baier, D.B., Gatesy, S.M., Hedrick, T.L., Metzger, K.A., Gilbert, S.L. and Crisco, J.J., 2010. X‐ray reconstruction of moving morphology (XROMM): precision, accuracy and applications in comparative biomechanics research. Journal of Experimental Zoology Part A, 313(5), pp.262-279.

It is better to use non-magnetic stainless steel “Grid Material” for undistortion. The McMaster Carr part number for non-magnetic “austenitic” stainless perforated steel is 9358T45. 

Any staggered grid pattern will work with XMALab. For higher magnification images, a McMaster Carr grid with smaller spacing than 9358T45 may be more appropriate, such as 9358T11.

Instructions: Place the perforated grid flat and close to the surface of the image intensifier. Record an image. Load the grid image into XMALab when a new .xma file is created. Image intensifier distortion can change during an experiment day and certainly between experiment days. It is best to collect several grid images during the day, as well as several sets of calibration images.

If you need to try a different grid image from the same day, create a new .xma file with the new grid and calibration and then import your tracked trial(s) from the other .xma file. You should NEVER have to track XY points more than once. The raw XY points can be used with different grids and calibrations to find the best ones.

These Undistortion Instructions and McMaster Carr part numbers are now on the XMALab Bitbucket Wiki.

— Beth Brainerd
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Elizabeth Brainerd

Robert P. Brown Professor of Biology

Director, Keck XROMM Core Facility
Department of Ecology, Evolution, and Organismal Biology
Brown University, Box G-B210
Providence RI 02912
o: 401-863-9261
www.brainerdlab.org
www.xromm.org