Re: Back-ground Determination for Thyroid Bioassay

[Ccja@aol.com]

Have you tried counting the thigh of the assayed person for use as a
background? Also, EMI/RFI can be a significant problem, especially at I-125
energies, and below. We had a real problem with this (Canberra Series 20 MCA
/ 2x2" NaI ANSI standard probe), until I put the instrument on an APC Smart
UPS, which has network-grade line conditioning. Any instrument used for
serious counting should have as much isolation as is feasible, from the
garbage on the AC power lines. Have you tried counting simultaneously with a
portable instrumant? And, is your counting room underground?

Chris Alston