Fwd: Re: Exposure rate measurements for fluoro.

[Chris Alston <alstonc@odrge.odr.georgetown.edu>]

>On Tue, 27 Feb 2001 07:48:48 -0500 "Vincent Maier" <vmaier@geisinger.edu>
>writes:
> > Bob:  While it may seem contradictory, 1020.32 (d)(3) states that
> > "Compliance with paragraph (e) of this section shall be determined
> > as follows:" Section (iii) covers C-Arms and states that the
> > measurement shall be made at 30 cm from the II provided that the end
> > of the beam limiting device is no closer than 30 cm from the II.
> > The 38 cm you mentioned is for stationary fluoroscopes.  I think the
> > regulations have told you what the maximum entrance exposure rate is
> > and section (d)(3) tells you how to measure compliance.  Since the
> > regs tell you how to measure compliance, that's the way I would do
> > it.  If the entrance exposure rate on a large patient (i.e. skin
> > close to the beam limiting device) exceeds 10 R/min, so be it.  You
> > measured it according to the regs.
>
>                 But by doing that, we still are ignoring the other point 
> that says the
>machine shall not be operable at an exposure rate greater than 10 R/min
>where the beam enters the patient.  Furthermore, each of these two
>statements in the regs uses the word "shall."  That means to me that each
>of the statements is an absolute requirement, and so far no one has come
>up with a rationalization of those two points.  And it's that dilema I
>believe exists, without a definitive answer.
>
>         Look at this another way.  A machine with the source above the 
> table is
>measured at a point 30 cm above the table, with the beam limiting devise
>as close to the point of measurement as possible.  Therefore, this
>machine is restricted to a lower maximum output than one where the
>measurement is taken at 30 cm from the surface of the II, and the
>miniumum SID is greater than 38 cm.  So how can these two machines have a
>different maximum output just because they are manufactured differently?
>I think either we all have been missing something very fundamental, or
>the regs are written incorrectly.
>
>Bob Scott, CHP
>Roger Williams Medical Center
>Providence, Rhode Island
>bobscottchp@juno.com


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