FW: Lead Aprons

["Barlow, Agnes E." <BarlowAE@MASPO2.MAS.YALE.EDU>]

In some cases the State regulations actually specify the thickness of the 
lead aprons.
Here in CT, it is only the veterinary portions of the regulations that 
specify "not less than one-half millimeter shall be worn by the operator and 
any individuals in the room during the exposure."  I have heard of some regs 
[??NJ??]stating 0.5 for fluoro and 0.25 for other diagnostic applications. 
 Although one can buy 0.25 mm lead aprons, we had a tendency to buy 
replacement aprons all of  0.5 so we did not have to be concerned about 
someone taking a portable radiography apron into a fluoro room.

Aggie
203 737-2142
Agnes.Barlow@Yale.edu
standard disclaimer

 ----------
From: Joel E. Gray
To: Multiple recipients of list MEDPHYS
Subject: Re: Lead Aprons
Date: Thursday,August 07,1997 11:52AM

I know of no justification other than the fact that you probably can't
get lead thinner than 0.5 mm!!  And if you can it probably costs the
same or more than 0.5 mm lead.

The real answer requires knowledge of the workload, etc., so one can
determine the actual transmission and amount of radiation on the other
side of the wall.  NCRP 49 is in revision but I would suggest that you
take a look at the work of Ben Archer, Doug Simpkin, and Bob Dixon (That
is not a citation--rather do a search on all three authors) and you will
find the basis for recommendations on shielding that will be
forthcoming.  For example, new and more reasonable occupancy factors
will be used; new exposures per image are used to determine required
shielding, etc.

Another consideration in specifying shielding is ease of installation
and inspection.  If one wall required 0.2 mm, another 0.3 mm and the
remaining two 0.5 mm, it may be preferential to specify 0.5 mm in all
four walls for two reasons--  1) the construction crews do not risk
putting the wrong thickness in the wrong wall; and 2) it will be easier
to assure compliance when doing your acceptance testing.  This assumes
that the cost of the three thicknesses is similar and that you can,
indeed, easily get the thinner stuff.

Another consideration-- if you are specifying 0.2 mm or 0. 3 mm, Why???
Did you take into account the shielding of the inherent wall material,
be it drywall, concrete block, etc.?  If small amounts are needed then
it may be less expensive to replace drywall with concrete block.

Just some thoughts!!

          Joel


Joel E. Gray, Ph.D., Consultant
2804 Second Street Southwest, Suite 334
Rochester, Minnesota 55902
U.S.A.

Phone   507-286-8910
Cell Phone     507-269-4247
Fax     507-286-8910
e-mail     joelgray@sprynet.com







On Aug 6,  6:02pm, Chris Alston wrote:
> Subject: Lead Aprons
> Does anyone know the history of the racheting-up of the de facto
standard in
> equivalency, to the point where most everyone (I think) uses 0.5mm?
Does this
> seem like overkill to anyone? The amounts of leakage from fluoroscopic
source
> assemblies nowadays is extremely small, so almost all of the radiation
to
> which people are exposed (excepting the case in which a physician has
his/her
> hands in the beam) is Compton garbage scattered by the patient (and
other
> "objects").
>
> E.g., the half-value layer (Pb) for 30 keV is 0.02mm, if I'm reading
the Rad
> Health Handbook correctly. That's 12.5 half-values given by a 0.25mm
> Pb-equivalent apron, or a 99.98% reduction of the entrance exposure.
Does
> that seem insufficient?
>
> chris alston
> ccja@aol.com
>-- End of excerpt from Chris Alston