Indium-115

[Hue Lu <bioanlyt@miravant.com>]

Dear Radsafers,

I am posting a question for a collegue who is not a radsafe subscriber.
Please respond directly to me at bioanlyt@miravant.com and I will
forward your responses to him.

Thanks.
Hue Lu

____________________________________________________________________

I have a conondrum about isotope 115 of Indium.

Here's the facts:
1) According to the 77th edition of the CRC Handbook of Chemistry and
Physics 115-In (not the "metastable" 115m-In) this isotope has a
half-life of 4.4E14 years and  a natural abundance of 95.7%. The decay
is negative beta at 0.495 MeV.
2) According to Oak Ridge National Labs (who sell this isotope) this
does not even qualify for DOT "radioactive" status because it's less
than one nanocurie per gram. Cambridge isotope Labs does not consider
this isotope radioactive either.
3) The CRC says that 14-C has a half life of 5715 years and a negative
beta emission energy of 0.1565 MeV.

It seems as if Indium 115 has a higher emission than 14-C but why then
is it not regulated?

Am I misreading the CRC?

If 115-Indium were used for autoradiography in medical research what
level of sensitivity would be required to get an image?

Thanks in advance!!

Alex Hornkohl