Re: Lead Aprons

[tdc@ehssun.lbl.gov (Ted M. de Castro)]

>>Lead aprons used in Radiology are inspected annually. What are the
>>recommendations for action if a hole is found in the apron when inspected
>>under fluoroscopy? (this hole is less than 0.1 mm in diameter).

>>If one says that the hole is so small as to be of negligible effect, then 
>>how large must a hole be to warrant action?

I don't know of any recommendations as to hole size criteria BUT I have 
employed a few considerations of my own:

Quite simply - calculate the percentage of hole to percentage of attenuation 
by the lead.  Obviously if the percentage hole is one or 2 orders of 
magnitude less that the percent of x-ray the that the lead lets through - 
then it is insignificant.

Secondly - note where the hole is.

Thirdly - in having fluored literally thousands of lead aprons - following 
some over more than a decade --- I can tell you that holes or pinholes are 
seldom if ever significant and if they are they are usually due to some 
trauma to the apron clearly visible from the surface.

Far far more significant is damage due to folding and piling up arpons.  I 
have seen light lines from material displaced from folding - usually not of 
much consequence but an indicator of problems soon to come - to gross 
cracking.

The worse I have ever seen was one apron folded transversely and piled in a 
corner so many times that the folds caused cracks that caused the whole 
middle third to just drop down to the bottom.

BUT this kind of damage is seldom seen anymore since aprons are not made 
this way anymore.  With newer aprons worse I have seen is a general motling 
which I attribute to poor mixing in the formulation of the material.

BTW a side note .... whenever I get a new apron to survey I always measure 
its lead equivalence and have NEVER found even one to be not as advertised!  
They are usually very close.  AND this is whether I do this rigorously with 
a radiographic machine and precise lead filters - OR calibrate the kVp of an 
auto-brightness Fluoro to the lead thickness!!


Ted de Castro
tdc@ehssun.lbl.gov
University of California Lawrence Berkeley Laboratory
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Berkeley, CA 94720
(510) 486-5256
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