Re[4]: how many sensitive cells?

[tdc@ehssun.lbl.gov]

>The question was (in a left handed way) why is not risk proportional to
>the total number of cells subject to irradiation times the actual fluence
>at the cells.

In a way - it IS.  Kinda sorta.

>I think Ted's comment above in fact is agreeing with this underlying
>presumption. He is pointing out that the external field is not the same as
>that at the cells.

yes

>But I saw no comments on what I was trying to find out - Is the total
>number of cells  in the body that are possible proginators for cancer a
>constant across adults of widely varying sizes?  Or a constant to a
>reasonable approximation?

Oh I see - cell COUNT not cell MASS.  ie. do all humans have the same CELL
COUNT regardlessof mass??  I don't know but I don't think so.

I'd also suspect MASS is more important than NUMBER.

BUT what I was trying to say was:

IFF one takes LNT to be true ...... THEN the risk to the population
- be it the population of cells in and organism or individuals in a
community - is the SAME if all the cells (using the organism model) are
exposed to 1x rads or 1/2 to 2x or 1/1000 to 1000x.

LNT says this would hold, up to prompt effects.

So - when one calculates EDE one is calculating the risk to the organism AS
IF ALL CELLS WERE UNIFORMLY IRRADIATED - thus assuming the local variations
were within the realm of linearity - ie - no prompt cell mortalities since
dead cells cannot become cancerous (I think).

So - EDE DOES in fact mathematically attempt to weight TOTAL energy
deposited in TOTAL mass - ie, the Fluence to each and every cell - BUT
expresses this in units that are a "concentration unit" and thus averaging
over the organism/population is mathematically the same thing.