In-111 pentetreotide

[Mack Richard <MRICHARD@WPO.IUPUI.EDU>]

Our Surgery group has purchased some type of probe for use in
localizing tumors labelled with In-111 pentetreotide (commercially
available radiopharmaceutical).  Of course, they didn't bother to talk with
us (Radiation Safety) before they decided to pursue this.  Now they
want to know what radiation safety procedures apply (and they want to
know yesterday - sound familiar).  Based upon info from our nuclear
medicine dept and the package insert for the In-111, it appears that about
10% of the administered activity (5 mCis) remains in the patient after 48
hours.  It is difficult to determine what fraction of that remaining activity
will actually be located in the tumor - it's probably variable, depending
upon the tumor type and size (my opinion).

Assuming all of the residual activity is in the tumor results in a tumor
activity of about 0.5 mCis.  Using the gamma constant from the package
insert, this would result in an exposure rate at 1 cm of about 1.61 R/hr
(obviously somewhat dependent on tumor size, concentration, etc.). 
Using inverse square, the exposure rate at 0.5 M (estimate of whole
body exposure rate) would be about 0.64 mR/hr.

We are attempting to obtain info from the surgeons regarding proximity of
their hands to the tumor and the length of handling time of the tumor itself.
We are also attempting to find out where the tumor goes (Pathology?)
after it is removed.  Personnel monitoring (whole body and more
importantly, ring badges) are being considered; however, they have to
be sterile and surgeons don't like to be "encumbered" by ring badges. 
One of my staff intends to be present when they first use this thing - that
will probably provide the best info.

Advice from anyone with experience with this procedure would be
appreciated.  I'm sure I left out some important detail - if so let me know.  I
will also share our experiences with this as they unfold.

Usual disclaimers apply.

Mack R.