Re: thyroid phantom

[hickman3@popcorn.llnl.gov (David Hickman)]

Phantoms for Iodine are very easy. For I-131 and I-123 use any of the
standard phantoms (ansi/Iaea, RSD, or hybrid). All provide the same degree
of accuracy, however to obtain good precision (i.e. repeatble maesurements)
use a large surface area detector. The large area detector improves the
geometry, decreases the variability, however the drawback is it provides
more background and can measure photons from other parts of the body if not
properly shielded. These are trade-offs all of us must live with. An example
of what a large area detector does can be found in one of my HP articles
published last year on wound monitoring.

For I-125 you do not need a phantom. Go dig out an article entitled:Absolute
Determination of I-125, Nucleonics, June 1964, Vol. 22, No.6. Large area
detectors are also recommended for this measurement as well, however as the
Nucleonics article shows, geometry is a minor problem.




>I am looking for a thyroid phantom to do thyroid bioassay  (I-125, 
>I-131 and possibly I-123).   What is the current thinking on the various 
>types such as:   two sources  versus single source std. ;   water filled 
>versus solid plastic;   any recommedations for vendors or suppliers? 
>I appreciate your help.   
>
>HANS  RICHTER
>
>
David P. Hickman, Ph.D.