Re: Replacement Of TLDsa

["Sandy Perle" <sandyfl@earthlink.net>]

The criteria for replacing TLD elements is based on many factors, 
such as:

1. Type of heating (direct contact, using a hot finger or non-contact 
     heating, such as hot gas.

2. Total dose to the various TLD elements

3. Environment in which they are exposed, such as chemical 
    contaminants.

4. The card carrier itself, pouching of the teflon covering and any 
     other potential damage to the device in total.

The basis for determining whether or not to replace is evident if 
there is any significant residual response on the TLDs themselves, 
after repeated annealing is performed. I suggest that if you are not 
already, that glow curves be captured for the heating process, and 
visually inspect them. If the TLDs are passing annealing criteria, 
and, the glow curves look acceptable, then they can be used for a 
longer period of time.

The old criteria for contact heating, using a hot finger, used to be 
~ 50 reads. That number is currently an under-estimate of the TLD 
capabilities.


------------------
Sandy Perle
Technical Director
ICN Dosimetry Division
Costa Mesa, CA 92626
Office: (800) 548-5100 x2306 
Fax:    (714) 668-3149
  
sandyfl@earthlink.net
sperle@icnpharm.com

Personal Website: http://www.geocities.com/CapeCanaveral/1205
        
ICN Dosimetry Website: http://www.dosimetry.com

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