Cell size and FSC

Hi, folks,

I am relatively new to flow and have a question about how forward 
scatter relates to cell size. From some of the previous postings, I can 
imagine the short answer is "poorly," but I would be grateful if 
someone out there could tell me more. Specifically:

I have read that FSC is a (rough) measure of cell diameter, but also 
that it is a (rough) measure of volume. Presumably if one treats the 
cell as light-impermeable, it's closer to area, while if it's light 
permeable, it's closer to volume. Is this right? Assuming constant 
density (not a very good assumption, I know), is there a plot of this 
relationship somewhere that anyone can point me to? Or an explication 
of the theory? I would be happy enough if someone could say at least 
whether FSC scales (roughly) as area or volume.

Also, and this is perhaps naive, I assume that the voltage readout 
attached to FSC is actually a delta-V. Otherwise, I have trouble seeing 
how a larger FSC means a larger (generally speaking) cell, and not a 
smaller cell. Unless it is the case that the smaller the cell, the more 
light goes straight through but is *not* figured into the FSC because 
the intensity of this light is subtracted out/ignored in the measure of 
FSC?

I'd greatly appreciate it if someone could shed some light on this 
matter. Thanks!

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Ramy Arnaout, MD, PhD
Brigham and Women's Hospital
Department of Pathology
Harvard Medical School
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Ramy Arnaout, MD, PhD
Brigham and Women's Hospital
Department of Pathology
Harvard Medical School
Tel (617) 538-5681