Re: Therapeutic I-131 waste

["Dale E. Boyce" <dale@radpro.uchicago.edu>]

I thought I'd throw my 2 c$ on I131 excretion.  I131 is given to
at least three categories of patient.  Patients with Grave's
disease, hyperthyroidism, are given doses in the 1 to ten mCi
range.  They have large uptakes, but still a large fraction is
excreted fairly rapidly.  Post surgical thyroid ablations are
typically 30 mCi, the maximum permitted in an outpatient
procedure.  Their uptakes can still be substantial, however the
majority is excreted via urine in the first few days.  Finally,
the inpatient therapies for metastatic thyroid cancer are
typically 100 to 200 mCi.  The uptakes are a few percent and the
rest is rapidly excreted.  With this last group of patients the
excretion rate seems to usually be about a one day effective half
life.  We have seen patients hold on to it a little longer, but
I can't remember seeing anyone with more than perhaps as much as a two
day effective half life.  I believe the variability is a function of
both fluid consumption and kidney function.  My bet is that in the other
two types of therapies the circulating iodine is eliminated on
a similar time scale.

Hope this helps.  If you need help with planning room preps etc.
feel free.

Dale E. Boyce
dale@radpro.uchicago.edu