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February
5,
2009 -- 5:00pm EST
CT Heart Scans, Radiation and the Media
A
new study, published
yesterday in JAMA, describes a wide variation in
the measured radiation exposure from CT angiograms,
depending on
which of 50 centers did the scans, what methods were used and, to some
extent, which scanner was used. This report predictably resulted in
"glowing" headlines about CT angiograms -- and not the good
kind of glowing.... Here's a sampling:
However, the point of this study was not to show
that CT scans of the heart have suddenly been found to be dangerous!
In fact, the doses recorded at the high end were what was considered
"normal" less than a year ago (e.g.
NY Times, June 29, 2008). Strikingly, as the accompanying
editorial
by Dr. Alfred Einstein states:
"The estimated overall median effective
dose for CTA...was 12 mSv, somewhat less than the value reported
in several earlier studies using 64-slice scanners."
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What is actually real important news,
for both medical professionals and patients, is that,
using dose reduction strategies, CT angiograms of excellent quality
were done with exposures of only 2.1 mSv, approximately what New
York City residents are exposed to annually, just from walking
around. That's why I titled Angioplasty.Org's coverage, "CT
Scans of the Heart Can Be Done with Low Radiation Dose." That's
news!
And the implications for patients and professionals
are profound. If you are a patient, says Dr. Michael Poon, past
president of the SCCT, ask the imaging center where you have been sent
for a CT angiogram, "'What method are you using to lower the
dose?'
And if they don't know what you're
talking about, I would say, 'See you later!'"
For imaging professionals, the PROTECTION I study
in JAMA has a clear message: learn the latest dose reduction strategies
and work with your equipment vendor to implement them. With radiation
at these low levels, CT angiography may mount a challenge to the
most often-prescribed nuclear stress test, which carries radiation
doses from 12-21 mSv. Of course, you never read headlines such
as "Nuclear Stress Test Zaps Patients" because it's been around
so long.
Ever since multislice CT scanners
became available in
2002-2003, industry and the imaging profession have been
working on ways to reduce the radiation exposure. The PROTECTION
I study in JAMA shows some positive results, but since 2007, when
that data was collected, technology has advanced significantly
-- enough so that Dr. Tony DeFrance, for example, regularly
performs 320-slice scans with Toshiba's AquilionOne scanner at
1 or 2 mSv. Likewise, physicians such as Dr. Michael Poon are using
GE Lightspeed units, and getting in similar ranges. Philips and
Siemens have
also developed low dose strategies.
As evidenced at the start of this post, whenever
a study about CT angiography is published, the popular press jumps
on the story with accompanying "dreadlines", doing a disservice
to the technology, those who practice it, and certainly to patients.
A shining, and unfortunately rare, exception to
this recent spate of news stories, was Dr. Nancy Snyderman, Chief
Medical Correspondent for NBC News, who discussed her own CT heart
scan with Matt Lauer on yesterday's "Today Show" (video below).
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