Fwd: Fluoroscopic abdomen phantom

[Ccja@aol.com]

---------------------
Forwarded message:
From:	joelgray@M3.SPRYNET.COM (Joel Gray)
Sender:	medphys@LISTS.WAYNE.EDU (Medical Physics Listserver)
Reply-to:	joelgray@sprynet.com
To:	MEDPHYS@LISTS.WAYNE.EDU (Multiple recipients of list MEDPHYS)
Date: 97-09-25 12:22:13 EDT

AAPM published a report several years ago specifying phantoms for
dosimetry in diagnostic radiology.  There were three, I believe.  The
one representing the AP abdomen consists of a stack of 6 sheets, each 1
inch thick, of acrylic and 3 mm of aluminum.  This represents,
approximately, a 21 cm AP abdomen.

For the sake of clarity, simplicity, and sanity let's stick with these
phantoms as "standard" phantoms.  (I know the FDA has their own standard
phantoms but they are much more complicated than the AAPM ones.)  We
don't care if the phantom exactly mimics a patient--the most important
issue is that everyone is using the same phantom.  An example of this is
the ACR Accreditation Phantom for mammography.  There were lengthy and
heated arguments, which finally died out, as to whether this represented
a 4, 4.2, ... or 5.0 cm thick breast.  In reality, it does not
matter--what matters is that measurements made in Minnesota can be
compared with those made in California or New York!!

      Joel Gray, Ph.D.





On Sep 23,  1:48pm, Wayne F Johnston wrote:
> Subject: Fluoroscopic abdomen phantom
> This is a request for help from one of those government guys who visit
you
> from time to time.
>
> We are about to revise our rules (= regulations) and several of the
> proposed changes/additions give me pause.  The one generating this
request
> adds specificity in some ways to a requirement that a registrant
determine
> fluoroscopic skin entrance exposure rates annually.  One rate is to be
the
> maximum obtainable rate and the other is an assessment of a 'typical'
rate
> by interposing "sufficient attenuative material ... in the useful
beam" to
> simulate a patient with a 23 cm thick abdomen.
>
> "Sufficient attenuative material" implies a phantom to me.  My
question is
> whether there is a generally accepted phantom used for this purpose.
Or
> would some people use a PMMA  block or stack while others would use
> aluminum and still others would use some combination of materials?
And,
> even were all to choose the same material(s), would they use the same
> thicknesses and arrangements?
>
> I think the requirement should be more specific about the nature and
> dimensions of the "attenuative material."  Any comments would be
> appreciated either on MEDPHYS or to my E-mail address.
>
> (Usual disclaimers)
> wayne johnston
> NH Bur Rad Hlth
> wjohnsto@dhhs.state.nh.us
> 603-271-4842
>-- End of excerpt from Wayne F Johnston