volumetric strain measurement of a cylindrical specimen before and after deformation

Hi there,

Assume we have two images from a cylindrical specimen before and after deformation (during this deformation the volume of the sample has been changed). we know the initial volume of the sample and the deformation occurs symmetrically. so we can assume that the 2D image of this sample shows a central section of specimen. the overall sample volume is obtained by representing the sample as a series of stacked circular disks. for each disk, it is assumed that the thickness of the disk is equal to a vertical pixel, while the diameter is equal to the number of horizontal pixels of each disk. so the volume of each disk can be calculated by (pi*((number of horizontal pixel)^2)/4*one pixel (the height of a disk)). the volume of the sample is calculated as the sum of the volume of the disks. by knowing the initial volume of sample we can calibrate the calculated volume of sample in first image (before deformation). now we want to convert the calculated volume of sample in image 2 (after deformation) from pixel to engineering unit and compare it to initial volume. the question is how we can do that in MATLAB. if someone can provide the program I really appreciate it.