[ RadSafe ] It happened again

Dawry, Frank FDawry at med.miami.edu
Tue May 15 13:58:37 CDT 2012

A useful, but unfortunately unsettling, way to equate radiation is with the use of the concept called B. E. R. T. (Background Equivalent Radiation Time). John R. Cameron, Ph. D., coined the term "BERT" as a way to describe and appreciate radiation doses from x-ray and nuclear medicine procedures. Using effective dose as a basis, BERT describes the amount of time that would be necessary in order to receive the same dose from average background radiation. One (1) BERT is approximately equal to 3 mSv or 300 mrem.

Using this, a typical 25 mCi injection of Tc-99m Sestamibi, the product of choice in most nuclear cardiac studies, especially for obese individuals, gives a BERT of 5.2 years. A typical Tl-201 injection, which is used for the same purpose, gives a BERT of 7.5 years. 

Compare that to the BERT for a routine chest x-ray of 10 days, a dental x-ray of 1 week, or a BERT for a lower G.I. series of 2 years, and you can appreciate why the BERT concept never became very popular as a way to describe the relative risks of nuclear medicine procedures. It's easier and less frightening to simply say its "equal to a few X-rays or a diagnostic CT scan".



Message: 1
Date: Fri, 11 May 2012 13:45:25 -0400
From: Stewart Farber <SAFarber at optonline.net>
Subject: Re: [ RadSafe ] It happened again
To: "'The International Radiation Protection (Health Physics) Mailing
	List'"	<radsafe at health.phys.iit.edu>
Message-ID: <002701cd2f9d$d9197e70$8b4c7b50$@net>
Content-Type: text/plain; charset=us-ascii

Hi all,
Regarding the news article Joel posted about the Firefighter in Milford, CT
setting off a State Trooper's rad monitor as the two cars were in proximity,
the "small" amount of radioactivity [ 201Tl most likely vs Tc-99m]
mentioned in the article is discussed in some detail in the excellent full
paper about cardiac testing at the following reference:


>From the above for 201-Tl:  
"Whole-body radiation exposure after a typical dose (2 to 4 mCi) is
approximately 0.68 rad, and the kidneys are the organ exposed to the most
radiation. The relatively long half-life (T1/2=73 hours) and low energy of
201Tl are important considerations during imaging. The long T1/2 contributes
to its significant inpatient residence time and requires lower doses to
minimize risk of radiation exposure."

This kind of event happens regularly. Many years ago, a visitor on a tour of
the White House [when the public was taken on tours]  set off rad monitors
there because he had had a nuclear stress test.

The article at the link Joel supplied below also states:

"In the test, a small amount of a radioactive material is injected into the
veins and used to help track blood flow to the heart.
Though the amount of radioactive material used in the test is relatively low
-- equal to a few X-rays or a diagnostic CT scan -- it was enough to set off
a radioactivity detector in the state police car. "

As we know a "small amount" of radioactivity or dose is relative. Had a
release [ aka "spewing" as invariably used by the press in writing about any
release] from a nuclear plant like Millstone nuclear station in CT [ which
supplies power to over 1 million people in CT] resulted in a fraction of the
exposure and dose rate cited, even to one person, many professional
anti-nuclear scaremongers would be calling for shutting down every nuclear
plant in the region and be wearing out the word "Fukushima". "Ain't it
awful" :-)

Stewart Farber
farber at farber.info


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