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august 27, 2009
Elements of Danger — The Case of Medical Imaging
Michael S. Lauer, M.D.
Related article, p. 849
A ccording to the Book of Exodus, a man who
assaults another must pay a physician to heal
the wounds. A careful examination of the Hebrew
text reveals that the word “heal” appears twice;
the literal reading is “and heal
he shall be healed.” The 13thcentury medieval physician and
philosopher Nachmanides interprets this redundant phrase to
mean that physicians require
permission to heal, for “without
the warrant to treat, physicians
might hesitate to treat patients . . . ‘in that there is an
element of danger in every medical procedure; that which heals
one may kill another.’” This 800year-old warning seems self-­
evident, yet one might think
otherwise when one sees the way
modern physicians make use of
outpatient imaging.
Consider Jim, a 58-year-old
man with newly diagnosed angina pectoris, hypertension, and
hypercholesterolemia. His physician treats Jim’s conditions with
appropriate lifestyle advice and
medications. Jim and his physician believe he is receiving highquality, evidence-based medical
care that is supported by numerous large-scale, randomized trials.
So far, so good.
Jim’s physician then follows
common practice and refers him
for an exercise myocardial perfusion scan. The scan is mildly
abnormal — mild enough that
Jim’s physician is not ready to
rush him to coronary angiography but abnormal enough that he
feels uncomfortable ignoring it.
He refers Jim for computed tomographic (CT) coronary angiography, an increasingly common
test. The CT scan also shows
abnormalities, leading to an invasive angiographic procedure
that reveals mild disease. Jim is
happy to hear that he need not
undergo any further testing.
This story may not seem all
that interesting, yet by referring
Jim for three common outpatient
imaging tests, his physician inflicted at least two harms. First,
Jim incurred costs for procedures
of uncertain value, since no largescale, randomized trials have
shown that imaging in these circumstances prolongs life, improves quality of life, prevents
major clinical events, or reduces
long-term medical costs. Second,
Jim was exposed to radiation. As
described in the report by Fazel
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The New England Journal of Medicine
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841
PERS PE C T IV E
Elements of Danger — The Case of Medical Imaging
No. of Services per 1000 Beneficiaries
175
163
150
All methods
125
100
85
CT
75
72
50
MRI
42
25
24
18
0
0
PET
6
1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005
Growth in Use of Advanced Imaging under Medicare, 1995–2005.
Computed tomography (CT) and positron-emission tomography (PET) expose patients
to radiation; magnetic resonance imaging (MRI) does not. Data are from a 2007 analyRETAKE
1st
AUTHOR: Lauer
ICM
sis conducted by the Office of Inspector General, Department of Health
2nd and Human
REG F FIGURE 1 of 1
Services.
3rd
CASE
Line
4-C
Revised
EMail
et al. in this issue
of the
Journal
Despite
theseSIZE
harms, our medARTIST:
ts
H/T
H/T
Combo
(pages 849–857),Enon
Jim underwent ical
system sees2 col
nothing wrong
AUTHOR, PLEASE
two of the five outpatient imagwith NOTE:
Jim’s care. Most physicians
Figure has been redrawn and type has been reset.
ing tests that result in the greatwho
order imaging tests experiPlease check
carefully.
est degree of medical radiation ence no consequences for incur08-27-09
JOB: 36109
ISSUE:
exposure among
typical non­ ring costs for
procedures
of unelderly American adults. This ex- proven value. On the contrary,
posure causes a small but real they or their colleagues are paid
increase in the risk of cancer.
for their services, and their paJim’s story reflects outpatient tients don’t complain because the
practice that has become increas- costs are covered by third paringly common in the United States, ties. Patients are pleased to rewhich has the world’s highest per ceive thorough evaluations that
capita imaging rate.1 Between involve the best cutting-edge tech1993 and 2001, the number of nologies. Physicians can easily
myocardial perfusion scans in- defend their practices because
creased by more than 6% per year, their specialty societies argue
with no justification for their use that the procedures are “approbased on disease rates, health care priate.” The issue of radiation
disparities, or newly published, exposure is unlikely to come up
definitive randomized trials.2 because each procedure is conSince 1992, the number of CT sidered in isolation, the risks
scans obtained has quadrupled.3 posed by each procedure are low
Physicians are referring their pa- and seemingly unmeasurable, and
tients for so many imaging tests any radiation-induced cancer won’t
that as many as 2% of cancers appear for years and cannot easmay be attributable to radiation ily be linked to past imaging
procedures.
exposure during CT scanning.3
842
When skeptics complain about
excessive costs for unnecessary
imaging procedures, it is easy to
dismiss them for advocating restriction (even “rationing”) of services that logical constructs argue
should help. In the case of myocardial perfusion imaging — the
procedure responsible for more
radiation exposure than any other,
according to the report by Fazel
et al. — proponents (my colleagues and I among them4) have
argued that abnormalities detected on such scans are powerful
predictors of future clinical events.
It is logical, the argument goes,
that imaging tests may identify
patients for whom aggressive
therapies should improve the outcome. But this logic represents
only a hypothesis, not a proof.
One recent trial of myocardial
perfusion imaging in patients
with diabetes showed no improvement in the outcome despite an
accurate prediction of events.5
Prediction does not necessarily
lead to prevention.
Radiation exposure presents
a different kind of risk. Rather
than a problem of cost-effectiveness or of levels of evidence, irradiation represents a direct danger
imposed by a physician’s decision
to refer a patient for imaging.
Though the danger may be small,
it is cumulative and hence of particular relevance to the small but
substantial minority of people
who, like Jim, undergo clusters
of tests. Exposure to even moderate degrees of medical radiation
presents an important yet potentially avoidable public health
threat.3 Oncogenesis associated
with sublethal doses of radiation
goes unrecognized because it is
neither accurately measurable in
nor predictable for individual pa-
n engl j med 361;9 nejm.org august 27, 2009
The New England Journal of Medicine
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Copyright © 2009 Massachusetts Medical Society. All rights reserved.
PE R S PE C T IV E
tients, and because clinically significant consequences will not
become evident for many years.
Overall, we must conclude that
with a few exceptions — such as
mammography — most radiologic imaging tests offer net negative results. There is little highlevel evidence of benefit, whereas
cumulative radiation exposure can
produce real harm, even if it may
not be possible to trace adverse
outcomes to individual patients
who have been exposed. If we
approached this component of
medical practice with the humility of Nachmanides, we would
have to wonder not only why so
much imaging is being carried
out but also why its use is increasing so rapidly (see graph).
Because the use of ionizing
radiation carries “an element of
danger in every . . . procedure,”
we need to adopt a new paradigm for our approach to imaging. Instead of investing so many
resources in performing so many
procedures, we should take a step
back and design and execute desperately needed large-scale, randomized trials to figure out which
procedures yield net benefits. This
approach would require leadership and courage on the part of
our profession, our opinion leaders, and the research enterprise,
but were we to insist that all, or
Elements of Danger — The Case of Medical Imaging
nearly all, procedures be studied
in well-designed trials, we could
answer many critical clinical questions within a short time. Because we will continue to be uncertain of the magnitude of harm,
an accurate understanding of the
magnitude of benefit is a moral
imperative.
To adopt this paradigm, we
will have to take two critical
steps. First, we must approach
imaging with the same humility
with which others in our profession approached experimental
methods for treating acute coronary syndromes and other conditions that today have a strong
evidence base. We have come a
long way since the time when
the primary management of acute
myocardial infarction was prophylactic lidocaine. Many of the
interventions that we now consider standard do come with
their own elements of danger,
but we can feel comfortable recommending them because a large
body of data from well-powered
randomized trials has clearly
shown a net benefit.
Second, we must assume a
“public health” mind-set when
considering our roles with regard
to medical imaging. We have to
think and talk explicitly about
the elements of danger in exposing our patients to radiation. This
means taking a careful history
to determine the cumulative dose
of radiation a patient has already
received and providing proper,
personalized information to each
patient about the risk of iatrogenic cancer. If we began a national conversation about the dangers of ionizing radiation, it might
cause enough discomfort to stimulate demand for the high-quality evidence our patients deserve.
No potential conflict of interest relevant
to this article was reported.
The views expressed in this article are
those of the author and do not necessarily
reflect those of the National Heart, Lung,
and Blood Institute.
From the National Heart, Lung, and Blood
Institute, Bethesda, MD.
1. Farrell D, Jensen E, Kocher B, et al. Accounting for the cost of US health care: a new
look at why Americans spend more. Washington, DC: McKinsey Global Institute, 2008.
2. Lucas FL, DeLorenzo MA, Siewers AE,
Wennberg DE. Temporal trends in the utilization of diagnostic testing and treatments
for cardiovascular disease in the United States,
1993-2001. Circulation 2006;113:374-9.
3. Brenner DJ, Hall EJ. Computed tomography — an increasing source of radiation exposure. N Engl J Med 2007;357:2277-84.
4. Lauer MS, Lytle B, Pashkow F, Snader CE,
Marwick TH. Prediction of death and myocardial infarction by screening with exercisethallium testing after coronary-artery-bypass
grafting. Lancet 1998;351:615-22.
5. Young LH, Wackers FJ, Chyun DA, et al.
Cardiac outcomes after screening for asymptomatic coronary artery disease in patients
with type 2 diabetes: the DIAD study: a randomized controlled trial. JAMA 2009;301:
1547-55.
Copyright © 2009 Massachusetts Medical Society.
H1N1 Influenza, Public Health Preparedness,
and Health Care Reform
Nicole Lurie, M.D., M.S.P.H.
I
n December 2009, the Department of Health and Human
Services will present to Congress
its first-ever national health se-
curity strategy, outlining highpriority activities and areas of investment for strengthening the
capability of the United States to
prepare for, respond to, and recover from large-scale public
health emergencies. Fortunately,
the strategy is being developed
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The New England Journal of Medicine
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Copyright © 2009 Massachusetts Medical Society. All rights reserved.
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