For scattering, you can consider the example of a suspension of  spherical particles. From Mie theory you can have the extinction efficiency  Q (https://en.wikipedia.org/wiki/Mie_scattering) . Then the mean free path is  l=2d/(3 phi Q)   with d diameter of particle and phi the volume fraction of particles. From Mie you can also calculate the asymmetry coefficient g ( -1

Amir,

With 'diffuse optical tomography' as a keyword, I assume you're working in the diffusive regime (and are so interested in reduced scattering).  There have been several detailed descriptions of phantom instrument calibrations for diffuse optics published in the literature:

MedPhot

http://www.ncbi.nlm.nih.gov/pubmed/15838951

nEUROPt

http://biomedicaloptics.spiedigitallibrary.org/article.aspx?articleid=1897756

Depending on your particular problem, you may also be interested in practical recipies- the appendix of PhD theses is a good place to look.  For phantoms made with Intralipid, I've used Regine Choe's emperical recipies:

http://www.physics.upenn.edu/yodhlab/theses/regine_choe.pdf

http://www.physics.upenn.edu/yodhlab/theses/david_richard_busch.pdf

Note: there is batch to batch variation in Introlipid, Lipofunden, and milk, so there will be some variation in the actual scattering of phantoms produced from these recipies.

The Oregon Medical Laser Center is an excelent place to find spectra of various tissue and phantom components:

http://omlc.org/

Most inks used in phantoms can be measured in a standard spectrophotometer and diluted as necessary for the desired absorption in the phantom.

regards,

David

Thanks all! very helpful.