calculate dimension of 3D nature objects

[igor.yung]

Hello!
Could you please help me with this task:
i have a stack of images from confocal microscope, each image is a xy scan of a human cell, and each image is from different z position of microscopic scanning, so a whole stack is a 3D image of a cell.

I need to know fractal dimension of this image (dimension of a distribution of points in 3D space). Images can be binary, but prefere greyscale, or it can be exported to the file with coordinates and intensites.

I use ImageJ programm to analise microscopic data, it have plugin FracLac, but it works only with 2D images, as i understand. Maybe you know any program (free is it possible), wich can do that task.
thank you)