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Re: RADSAFE digest 3384 (extremity dose)

Bruce Busby wrote, regarding suggested use of wrist badges to replace rings:

"Thanks for the note. We have looked at that, but a lot of our sources are
small. Do you worry about being called to task for the same problem as
Mallinckrodt had, by measuring so far from the finger tips?"

If individuals are directly handling unshielded sources without remote handling, 
then fingertip badges are needed (assuming significant dose is being received*).
Our policy is to discourage any direct handling of unshielded activity at any 
activity levels, not just because it's good practice, but because otherwise we
can't accurately measure the dose.  One example: 40 microcuries (1.5 MBq)
of Y-90 in a HPLC micro-sample vial (~0.2 ml glass vial) delivered 90 mrad to
a Landauer X-8 TLD chip in a minute, with the chip held against the side of the 
vial.  That's over 5 rad/h (0.05 Gy/h) from a 40 microcurie sample!  Watch out
for any high energy beta in a thin wall container (e.g. P-32 in microfuge tubes),
even at seemingly trivial activity levels.

*and assuming that fingertips are used to handle the activity, rather than the
entire hand.  If the whole hand is in contact with the source, then the ring badge
has a decent chance to measure the dose properly.  With physically small
sources, the likelihood of fingertip handling increases.


And Jim Barnes wrote:

"Several years ago I remember seeing a finger dosimeter 
that was embedded in a plastic finger sleeve that fit 
over the top of the finger.  They were very flexible and 
fairly strong.

I don't know if they were ever released commercially 
(anybody know???), but if so, they might be a good 
substitute for rings."

Vinten dosimetry (in England?) made these.  I tried tracking them down and 
heard that maybe Bicron had them.  I was unsuccessful in finding anyone
who was willing to offer them as a dosimetry product unless you bought 
your own reader etc for big bucks.  Maybe I just talked to the wrong person.
If you have better luck, let us know.

Regards,

John R. Laferriere, CHP
DuPont Pharmaceuticals Co.
Medical Imaging Division
john.r.laferriere@dupontpharma.com
(978) 671-8316   fax (978) 671-8149
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