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[cdn-nucl-l] Re: [Rad_Sci_Health] Boreham, Scientists find low-dose radiationa benefit; Fw: Brenner/Hall paper on CT scans an hypothetical cancer risks
- To: <Jodi.Strzelczyk@uchsc.edu>, "Cuttler, Jerry" <firstname.lastname@example.org>, <CDN-NUCL-L@mailman1.cis.mcmaster.ca>, ANS-PIE <email@example.com>, <firstname.lastname@example.org>
- Subject: [cdn-nucl-l] Re: [Rad_Sci_Health] Boreham, Scientists find low-dose radiationa benefit; Fw: Brenner/Hall paper on CT scans an hypothetical cancer risks
- From: Ted Rockwell <email@example.com>
- Date: Tue, 04 Dec 2007 13:14:40 -0500
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Title: Re: [Rad_Sci_Health] Boreham, Scientists find low-dose radiation a benefit; Fw: Brenner/Hall paper on CT scans an hypothetical cancer risks
My msg below was intended to refer to the Brenner/Hall paper, not Doug’s excellent article. Sorry if that was not clear.
On 12/4/07 1:01 PM, "Ted Rockwell" <email@example.com> wrote:
That’s a pretty mealy-mouthed statement, trying to protect the CT business while not really questioning the many statements in the article that are demonstrably wrong.
Brenner & Hall are not objective scientists presenting the full story on a “controversial” subject, they are virulent advocates for a discredited position.
On 12/4/07 12:50 PM, "Jodi.Strzelczyk@uchsc.edu" <Jodi.Strzelczyk@uchsc.edu> wrote:
Indeed, this article puts things in perspective. Great job, Doug!
Numerous professionals and groups were disappointed with this review article where either old or irrelevant epidemiological data are further molested. Some examples are attached and here is a link to the AAPM statement:
Jadwiga (Jodi) Strzelczyk, Ph.D.
Associate Professor, Radiology, UCDHSC
UCH Radiation Safety Officer
AMC, Leprino Building, Mailstop L954
12401 E. 17th Avenue, Room #5-547
P.O. Box 6511
Aurora, CO 80045
From: Rad_Sci_Health@yahoogroups.com [mailto:Rad_Sci_Health@yahoogroups.com] On Behalf Of Jerry Cuttler
Sent: Monday, December 03, 2007 8:36 PM
To: Canadian Nuclear Discussion List; ANS Member Exchange Listserv; Rad_Sci_Health
Subject: [Rad_Sci_Health] Boreham, Scientists find low-dose radiation a benefit; Fw: Brenner/Hall paper on CT scans an hypothetical cancer risks
Nice article ...
Scientists find low-dose radiation a benefit
The Hamilton Spectator (Dec 3, 2007)
In a disturbing study published recently in the New England Journal of
Medicine, U.S. researchers claimed that 2 per cent of all cancers in coming
decades will be caused by routine diagnostic CT (computed axial tomography)
(The report, by two researchers at Columbia University, said the average
American's total radiation exposure has nearly doubled since 1980, largely
because of CT scans. About 62 million CT scans were done in the U.S. last
year, up from three million in 1980. More than four million were on
children. CT scans use X-rays. MRI and ultrasound procedures do not.)
There are a number of biological issues that make the type of estimation in
the Columbia University report inappropriate.
For decades, scientists have been trying to estimate cancer risk associated
with low-dose exposure by estimating the risk from very high-dose exposure.
The fact is, it is difficult to estimate risk from high, acute exposures
down to very low exposures without solid scientific data to support the
Researchers at McMaster University, for instance, are involved in studies
focused on the actual biological risks associated with low- and very
There are many biological reasons why risk extrapolations from high doses
are not consistent with real risks at low doses.
First, cancer risk estimates from high-dose exposures come from
epidemiological data from atomic bomb survivors. Radiation-induced cancer
risk in a war-torn population of Japanese people 62 years ago is vastly
different than cancer risk in North Americans today.
It is known even today that cancer risks between the two populations are not
similar because of different genetic backgrounds and environments,
regardless of radiation exposure. Adding radiation to the equation only
compounds the difficulties of comparing cancer risks between the two
Cancer risk increases when the doses are high and acute, whereas most
medical procedures use low dose, from which no increased cancer risk was
observed in the A-bomb survivors. Therefore estimating cancer risk in a
modern North American population exposed to very low-dose radiation based on
data from high-dose exposures in A-bomb survivors is almost impossible.
In cancer risk estimations, it is assumed that all doses of radiation are
risky and the risk is simply proportional to the dose. However, there are
hundreds of scientific publications to show this is not the case.
At low doses, biological response mechanisms can eliminate minor damage
caused by low-dose radiation and restore things back to normal with no
At high doses, other mechanisms are used as an emergency defence for
survival but these systems tend to be error-prone and consequently increase
Overall, biological mechanisms responding to low doses are different than
those at high doses. Therefore, assuming the biological risk is the same at
all doses is biologically flawed.
There are also hundreds of scientific reports that support the idea that
low- dose radiation is a necessary environmental agent required for life.
Our research at McMaster University has shown that low doses can have
beneficial effects to living organisms, and a large research study is
currently under way to test the idea that low-dose CT scans actually reduce
Studies that investigate risk based on total dose are questionable if the
total doses have been additive, like adding up the entire dose from several
CT scans, because evidence supporting the idea that total risk is also
additive is lacking. It's like taking a bottle of medicine all at once
(which can be harmful) as opposed to taking small doses of it over a period
of time (which can be beneficial).
If a radiation dose is spread out over a period of time (split or
fractionated), like multiple CT scans done over a period of time, the
biological consequences are known to be reduced because allowing time
between the exposures allows cellular repair processes to eliminate the
effects of the prior dose. So the risk is not proportional to the total
Therefore assuming that the total additive dose from multiple CT scans,
which is the high total dose required to make the calculated estimated
cancer risk from A-bomb survivor data, has the corresponding additive
biological risk may not be accurate.
Also, there are many published reports, other than those on A-bomb
survivors, in populations exposed to low doses of radiation comparable to
doses from CT scans, which show cancer mortality is not increased at these
Based on actual biological scientific evidence, and not calculated
extrapolation, an opposite conclusion about CT cancer risk is equally
plausible. That is, cancer risk in North America may be reduced by 2 per
cent over the coming decades because of low-dose medical CT exposures.
Studies that warn of increased risk based on calculations from high-dose
extrapolation from any genotoxic agent should be viewed with caution,
considered hypothetical, and also potentially detrimental since
misinformation can sometimes cause undue harm.
Doug Boreham is an associate professor in the department of medical physics
and applied radiation sciences in the McMaster University Institute for
Applied Radiation Sciences.
----- Original Message -----
From: Scott, Bobby
To: howard long ; Jerry Cuttler ; Carmel Mothersill
Cc: firstname.lastname@example.org <mailto:2007.aapm%40aapm.org>
Sent: Monday, December 03, 2007 6:10 PM
Subject: FW: Brenner/Hall paper on CT scans an hypothetical cancer risks
From: Scott, Bobby
Sent: Monday, December 03, 2007 11:32 AM
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Subject: Brenner/Hall paper on CT scans an hypothetical cancer risks
You are probably aware of the media coverage of the new paper by D.J.
Brenner and E.J. Hall entitled "Computed Tomography - an increasing source
of radiation exposure" that was published in The New England Journal of
Medicine 357:2277-2284, 2007. Brenner and Hall extrapolated from high-dose
cancer data associated with the atomic blasts that took place in Hiroshima
and Nagasaki to low doses of X-rays from CT scans in clinical settings in
the United States, via using the linear no-threshold (LNT) model. The atomic
detonations involve gamma rays, neutrons, blast propelled projectiles, and
thermal waves. The population response involved combined injuries (wounds,
thermal burns, neutron/gamma-ray induced damage) and recovery in devastated
cities. Without adjusting for such combined injuries, adverse environmental
effects, differences in genetic susceptibilities of the Japanese and U.S.
populations, and using hypothetical low-dose cancer risks, Brenner and Hall
calculate that in coming decades, 2 per cent of all cancers in the U.S. will
be caused by routine diagnostic CT scans.
Attached is an article published today in The Hamilton Spectator that
presents a different perspective on low-dose radiation risks associated with
CT scans. The article was written by Doug Boreham of McMaster University and
is entitled "Scientist find low-dose radiation a benefit". I thought you
may like to know about the article.
Bobby R. Scott, Ph.D.
Lovelace Respiratory Research Institute
2425 Ridgecrest Drive SE
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