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Re: Prostate Misadministration
>References: <35622663.F998E8B4@concentric.net>
>Date: Tue, 19 May 1998 21:46:29 -0500
>Reply-To: Medical Physics Mailing List <MEDPHYS@LISTS.WAYNE.EDU>
>Sender: Medical Physics Listserver <medphys@lists.wayne.edu>
>From: "P. King" <pking@CYBERTRON.COM>
>Subject: Re: Prostate Misadministration
>To: MEDPHYS@LISTS.WAYNE.EDU
>
>Our regs specifically exclude dose errors caused by the motion of seeds
after the seeds
>are in place. Seems pretty obvious. I suppose that if the regs were
worded poorly, it
>might be possible for a patient's prostate to violate state regulations by
swelling up
>after an implant.
>
>Though you might see a 25% difference between pre-implant and post-implant
calculations,
>I don't think that should lead you to say that a 25% dose difference is not
clinically
>significant -- even if in this case, it does not indicate a "problem" or
"error". If
>you did the pre-implant calculations correctly, the doc approved the dose
distribution
>and put the seeds in according to the arrangement you designed, you
calibrated the seeds
>and they went in at the correct activity, in an area which was vaguely the
prostate of
>the right patient -- I don't think you have room for a misadministration.
(This is not
>to say that there is not room for a seriously messed-up implant.)
>
>I suggest that some reasonableness needs to come into play when complying
with these
>radiation control regulations unless you want the state regulators standing
in the OR
>with you.
>
>If it seems like I'm a little wound-up, I just finished a 3 hour FDA
inspection.
>
>Paul
>
>
>
>Shackie wrote:
>>
>> Here's a question for you folks involved in the prostate implant
>> planning and documentation:
>>
>> How do you avoid reporting "regulatory misadministrations" which are
>> probably clinically insignificant? Or, stated in another way, how is the
>> dose stated in the written directive to limit the misadministration
>> reports to cases of significant misses? I have a sense that not many
>> reports are being submitted to the NRC or the states since I have not
>> seen any red flags being waved from those groups.
>>
>> I think that most folks plan an implant to get the minimum peripheral
>> dose (mPD) to whatever prescription dose the doc wants. But it is also
>> documented that the delivered mPD is generally less than planned by an
>> amount that is unpredictable and often by more than 25% (Yu et. al.
>> IJROBP, v34,3, 717-725, 1996). Since misadmin. is a deviation of more
>> than 20%, that would be a lot of reports IF mPD is the dose in the
>> Written Directive (aka prescription).
>>
>> We are currently using a regulatory "loophole" (which I hope stays in
>> the revised regs.). In our state regs. it is stated that the written
>> directive must contain:
>> "After implantation but prior to completion of the procedure: the
>> radionuclide, treatment site, and total source strength and exposure
>> time (or, equivalently, the total dose)." So, our directives have the
>> total ordered source strength before implant and the actual implanted
>> total source strength after implant as a modified directive filled out
>> before the patient leaves the OR. The exposure time is total decay
>> (actually the state wants the mean time).
>>
>> I think this alternative dose definition, and the two step pre/post
>> implant directive, which far predates the prostate implants, is a wise
>> flexibility provided by the regulators in recognition of the
>> difficulties associated with dose definition (in Gy) and delivery in
>> brachytherapy targets.
>>
>> Hobie Shackford MS DABMP
>> Medical Physicist
>> Roger Williams Medical Center
>> Providence, RI
>>
>> *****
>> Frequently Asked Questions (FAQ) for Medphys at:
>> http://www.mindspring.com/~sherouse/MPFAQ
>
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