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Re: Source for source (Am241) -Reply -Reply
>Content-Disposition: inline
>Date: Mon, 15 Jun 1998 16:23:38 +1000
>Reply-To: Medical Physics Mailing List <MEDPHYS@LISTS.WAYNE.EDU>
>Sender: Medical Physics Listserver <medphys@lists.wayne.edu>
>From: Daniel Schick <schickdk@HEALTH.QLD.GOV.AU>
>Subject: Re: Source for source (Am241) -Reply -Reply
>To: MEDPHYS@LISTS.WAYNE.EDU
>
>Other sources may well have their place but I feel that an Am241 source
>(or mobile X-ray source) is best suited to a non-destructive shielding
>check of a diagnostic X-ray room. Such a source was used regularly
>around Queensland (Australia) for a number of years until some recent
>problems with the scaler/ratemeter that was offered for hire from the
>regulatory authority along with the source.
>
>The source was particularly useful when the barrier in question included
>some other significantly attenuating material (e.g. single course of
>brickwork). To adequately characterise such a barrier either a source
>with 'diagnostic X-ray' range energy emissions or a dual energy
>technique are required. In fact because of the pedanticism of the local
>regulatory authority a few years back, even a couple of sheet
>thicknesses of gypsum wall board could throw out measurements performed
>with the 356keV emission of Ba133 if the aim was to distinguish between
>say 20 and 25kg/sqm (1.76 and 2.2mm) lead sheet.
>
>Having said the above, we have more recently been using a mobile X-ray
>and medium speed film/screen combination to test shielded walls around
>our hospital. This gives the advantage of a visual check on integrity of
>shielding at joins, overlaps etc. and more importantly recently allowed
>us to characterise a problem of corroding lead found to exist through a
>large section of our original Radiology department.
>
>
>>>> Michael Tkacik <mtkacik@SCSN.NET> 13/June/1998 06:56am >>>
>If you have access to a nuclear medicine department
>I would recommend using their Co-57 dose calibrator
>vial source. This Co-57 has the advantage of being solid and
>in a plastic vial, so you don't have to worry about
>contamination, even if you're a klutz. However, a good
>NaI detector is needed as the GM lacks sufficient sensitivity.
>
>-Michael Tkacik
>
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