From: frank@rover.uchicago.edu (Frank - Hardware Hacker - Borger)
Newsgroups: sci.med.physics
Subject: FDA just discovered Radiation Therapy Simulators
Keywords: Therapy Simulators
Date: 3 Sep 92 19:23:00 GMT
Reply-To: frank@rover.uchicago.edu
Organization: Joint Center for Radiation Therapy
News-Software: VAX/VMS VNEWS 1.41


	Anybody catch the latesst issue of the center for Devices and radio-
logical health Radiological Health Bulletin? Their lead article is:

FDA Draws Attention to Concerns about Radiation Risk from Fluroscopy

The article says in part...

As noted in the Letter to the Editor, a number of unverified, but disturbing,
anecdotal reports have reach FDA regarding extremely large radiation exposures
allegedly received by patients undergoing fluoroscopic procedures. ... Several
recent trends have increased the potential for such high-exposure events. These
trends include the increased use of fluoroscopic visualization to guide the
condeuct of therapeutic procedures, and the greater operational complexity and
radiation output capacity of some fluoroscopic x-ray systems.

Later it says in part...

adequate or appropriate attention may not always be given to the potential
radiation exposures and associated risks. ... Because these procedures are 
theraputic in nature, the risk-benifit evaluation may be different than for
diagnostic proceedures...

	From the above, I get a feeling that the writer didn't know much about
	simulators, in that:

	a/ Simulator fluro is often modified to have 4 or 5 times the maximum
	   output of conventional units, but only because the units are oper-
	   ated at about twice the normal target-patient and target-film dis-
	   tances. Patient exposure is no different than diagnostic use.

	b/ Simulation procedures are NEVER THERAPUTIC IN NATURE. They are only
	   done to precisely locate the tumor for precise treatment.

	c/ With normal radiation therapy treatments delivering doses on the
	   order of 30 to 50 Gy, and absolute uncertanties in dose on the
	   order of 3 to 5%, we're talking on variations on the order of
	   1 to 2 Gy from patient to patient. To deliver 1 Gy with our fluro
	   unit, (80kv, 16ma) will take me approximately 16 minutes of exposure.

Do we have a potential problem here? Is the FDA going to come lumbering in and
apply rediculous, diagnostic based, limits on simulator operation?

Added footnote: Yesterday an associate from Diagnostic Radiology brought an FDA
inspector to our department to ask about a recent recall warning about the
treatment table for our CO60 unit. (Don't ask me why the FDA inspector went
to diagnostic radiology instead of radiation therapy to look for a CO60 unit.)

I told the inspector, "Yes, I received the recall notice but it doesn't apply
to our unit. We bought it without the treatment table, and we treat emergency
patients only, and treat them on a gurney."

The inspector then asked me, "What's a gurney?"

Boy do we have a lot of educating to do!


   Frank R. Borger - Physicist    __       Internet:  Frank@rover.uchicago.edu
Michael Reese - Univ. of Chicago |___      Phone : 312-791-8075 fax : 567-7455
  Center for Radiation Therapy   | |_) _   
    2929 South Ellis Avenue        | \|_)  You may already be a looser... Form
    Chicago, Illinois 60616           |_)  letter received by R. Dangerfield