Re: Re(2): Radionuclide impurities in Therapeutic Dosages

[Ccja@aol.com]

Franz

Gene is, in fact, asking about the therapeutic use of radiopharmaceuticals.
Note that the Mo99 parent, with which the column is impregnated, has a
halflife of 66h. Tc99metastable has, as we know, a 6h halflife. The "true"
daughter (hopefully the PC Police aren't monitoring), Tc99, has a halflife of
2x10E5 y. How could there be time for measurable, never mind significant,
ingrowth? It happens in reactors because they're continuously producing Mo99,
as one of the primary fission byproducts. But, if you start with a fixed
quantity, which can only decay, it will all be gone in a month. Maybe I'm
missing something badly here; if so, please hasten to enlighten me.

I suggested, in an earlier post, that it seemed as though the spirit of the
regulations was that the committed effective dose equivalent, to the patient,
be within 10 percent of that explicitly stated, or implied, by the
prescription. Presumably, the demonstration of that would have to take
account of any impurities present. I'd hoped for a comment by a regulator,
but I haven't seen one.

Chris Alston

P.S. How would an in vitro study give a dose to a patient?