View Full Version : Visible Female CT data calibration factors

05-24-2005, 08:54 AM
Biomch-l subscribers:

We are segmenting the Visible Female CT dataset for the bones of the
head and neck region and found that the pixel calibration factor
(mm/pixel) changes as we look at images from the skull down the neck.
Specifically, it is 0.488 mm/pixel from the skull to mid-C4 (slice
1209), then becomes 0.723 for the next 17 slices, changes to 0.859 for
the next 20 slices and finally becomes 0.938 down to slice 1400 (this is
as far as we've examined). Presumably this was done to change the field
of view as the body cross-sectional area increases caudally.

Our problem is that the image analysis software we use (3D-doctor, Able
Software) does not allow for changing calibration factors in one stack
of images. (That is, the calibration factor given in the first image
header will be used for all images in the stack). The best solution we
have come up with seems to be to define different image stacks with
different calibration factors, segment the bones separately, export to
another format, scale and re-combine the data for 3-D rendering.

We would like to know if anyone else working with the Visible Female or
other dataset has come across this problem and has any more elegant
solutions. Or, are there other software packages that allow different
calibration factors for different images in one stack? As always I will
post a summary of responses.

Anita Vasavada

Anita Vasavada, Ph.D.
Assistant Professor
Programs in Bioengineering and Neuroscience
Washington State University
Pullman, WA 99164-6520
voice: (509) 335-7533
fax: (509) 335-4650