[ RadSafe ] Update on lead aprons in nuclear medicine

Wed Aug 27 03:22:59 CDT 2014

This issue is further complicated by the fact that most of today's newer imaging machines are also CT units, i.e. PET/CT or SPECT/CT.  The best policy is to fully utilize the concepts of Time (minimize time around the patients after they have been injected with imaging agents), Distance (maximize distance from the patients, i.e. stay far away from the patient by being inside of the shielded control booth as much as possible and don't "hang" out around the patient's gurney in the imaging suite), and Shielding (use syringe shields or better yet robotic injectors, and stay in the shielded control booth).  Time, Distance, and Shielding for a Nuclear Medicine Department is very different from a standard X-Ray imaging facility.  Prior to the use of combining Nuc Med imaging with CT units the walls in Nuc Med facilities were typically unshielded due to the prohibitive amount of shielding required.  Now the walls are shielded to meet the CT needs, which
 aren't even close to meeting the energy requirements of Tc-99m or FDG.  The shielding requirements for a PET facility are considerable due to the 511 keV emissions.  In my humble opinion, the biggest difference between a standard X-ray facility and a Nuc Med Department is that the emissions from an X-ray tube only occur for fractions of a minute many times over the course of a day, where as in Nuclear Medicine the patients are injected with their imaging agents and then their sent to a waiting room for an hour, then their imaged for approximately 30 to 40 minutes, and then their asked to wait while their images are processed.  The whole time a Nuc Med patient hangs around in the Nuclear Medicine Department they are giving off emissions, and since many departments have several cameras there are usually several patients hanging around at any given time.   Lead aprons just wouldn't be practical. 

Roy Herren

On Monday, August 25, 2014 5:46 PM, Ted de Castro <tdc at xrayted.com> wrote:

With respect to the energy at which they are equivalenced - I'd suggest 
around 90 or so kVp DIRECT diagnostic xray beam.

I say this from my own experimental results.

As a consultant doing annual x-ray machine "calibrations" as local 
hospitals I would also check their aprons for defects and every apron 
got checked at least once for equivalence.

At first I did this the traditional way - set up an attenuation curve 
with calibrated lead filters on a test stand - and then measured the 
attenuation through the garment using a standard radiographic unit.  
(which I had already verified for consistent performance!)

Later I found it quicker and just as accurate to calibrate the 
auto-brightness kVp on a fluoro unit with the calibrated lead filters 
and then just run the garments under the fluoro and note the kVp - thus 
I could inspect and verify equivalence at the same time. Considering in 
a given hospital there would only be two or three different 
"thicknesses" to verify - this was certainly sufficient and efficient.

No, this was not a 5 decimal point verification - however, as I recall 
without looking at old reports, the results were pretty close to the 
label - if any were less than the spec on the label I would have brought 
that garment to their attention and I don't recall ever having to do 
that.  Creases, tears, holes and in one case completely missing sections 
- sure - but never and equivalence issue.

On 8/25/2014 3:42 PM, Lemieux, Bryan P wrote:
> Hello,
>
> You also need to look at what energy the lead equivalence is at.  Many of these composite materials are only "lead equivalent" in the energy range for scatter x-rays from diagnostic energy x-ray beams..... Get the manufacturer data on the actual attenuation properties by energy to see what it would be for your gammas.
>
>
> Bryan Lemieux, M.S., CHP
> Radiation Safety Officer
> University of Tennessee Health Science Center
> 3 N Dunlap St. S110 Van Vleet Bldg
> Memphis, TN 38163
> Phone:  901-448-6114
> Fax:      901-448-7774
>
>
>
> -----Original Message-----
> From: radsafe-bounces at health.phys.iit.edu [mailto:radsafe-bounces at health.phys.iit.edu] On Behalf Of Jeremy Nicoll
> Sent: Monday, August 25, 2014 5:33 PM
> To: The International Radiation Protection (Health Physics) Mailing List
> Subject: Re: [ RadSafe ] Update on lead aprons in nuclear medicine
>
> I'm not quite sure what you're working with, how much and how close, for how long etc., but the HVL for Tc-99m gammas is 0.3 mm Pb, so that should let you do some calcs.  If the thicknesses you talk of are Pb equivalences then the apron isn't going to do a lot, compared with the inconvenience of wearing it, and the thyroid shield, and perhaps the Pb glass specs.
> I don't know of any Nuc Med unit where aprons are worn routinely for RP.
>
> Jeremy
>
> Dr Jeremy J Nicoll
> Radiation Safety Advisor
> University of Otago
>
>
> -----Original Message-----
> From: radsafe-bounces at agni.phys.iit.edu [mailto:radsafe-bounces at agni.phys.iit.edu] On Behalf Of Ålund Maria
> Sent: Thursday, 21 August 2014 12:16 a.m.
> To: radsafe at agni.phys.iit.edu
> Subject: [ RadSafe ] Update on lead aprons in nuclear medicine
>
> Hi,
>
> I am wondering if the lead aprons has ben improved for nuclear medicine workers the latest years. I read a question dated from 1997, *Lead aprons in nuclear medicine,* (*http://health.phys.iit.edu/extended_archive/9703/msg00011.html
> <http://health.phys.iit.edu/extended_archive/9703/msg00011.html>) *that stated that lead aprons suitable for x-rays is not necessarily enough shield to be used for gamma rays. Are the composite aprons that weight less equal as good as a conventional lead apron nowadays? And which thickness should then be used? The aprons that are being used at my workplace is made of the composite material and has the thickness of 0.25 and 0.35mm. The radiophysics says that this is enough.
>
> Thanks for your help.
>
>
>
> Maria Ålund
>
> Biomedical scientist, Sweden
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