A silent, hidden threat continues to gain power in our nations medical apparatus. It is
threat which makes no sound, is completely invisible to the eye and stimulates no
senses. Yet it’s power to impact human health in a profound and powerful way is clear
and undisputed. The name of this threat is Ionizing Radiation.
There are several types of radiation found in nature, but ionizing radiation remains
notable for it’s ability to damage human genetic material and exert physiologic effects in
the body. In an era when medical imaging is routine and as accessible to this
generation of physicians as stethoscopes and reflex hammers were to previous ones,
the problem of medical radiation remains an unseen but deadly manifestation of modern
medicine.
The story is one which plays out thousands of times a day in every hospital, clinic and
emergency room in the developed world. A patient presents with a nebulous medical
complaint and the physician taking care for them must answer a critical question:
Should this person undergo medical imaging or not. This decision might not be so
vexing were it not for the long list of harms and benefits that accompany it. It is
estimated that ionizing radiation from medical imagining now accounts for half the
overall radiation exposure in the US each year.
While some medical imaging studies offer harmless non ionizing radiation (like MRI) or
small doses of harmful ionizing radiation (X-ray) among the most widely used imaging
studies is the CT scan which gives a massive dose of ionizing radiation. A single CT
scan provides more ionizing radiation than 200 Chest X-Rays. Despite the radiation exposure, CT scanning remains increasingly among popular among physicians with use of the CT scanner growing exponentially over the past several decades. It is estimated that use of CT scanning in the United States has tripled since 1993.
The effects of all this radiation on the population is far from miniscule. Studies
estimate that the lifetime radiation dose of a few CT scans (how many depends on
which part of the body is being scanned) is comparable amount of ionizing radiation to
being in Hiroshima on the day the atomic bomb went off. One particularly controversial
study estimated that 1.5-2% of all future cancers in the United States will be because of
medical radiation. Another study estimated that CT scanning increase any one
individuals risk of cancer by .35% and while this may not sound like much on a
population level that would translate into tens of thousands of cases of cancer per year.
In fact another study estimated 29000 cases of cancer caused by CT scans done in
2007 alone.
And yet The CAT scan has changed the way medicine is practiced. It was not long ago
when physicians had to rely on history and physical exam to make the diagnosis. CAT
scans gave physicians an accurate, objective way of seeing exactly what was
happening inside our patients that exceeded the power of our own senses.
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Anyone who has ever practiced medicine understands that the idea behind any medical
intervention is that the therapeutic benefits of doing something that could cause harm
outweigh the risks. The same rules should apply to CT scanning. There are many
indications where the relatively small individual increased risk of cancer from giving a
CT scan is outweighed by the benefit of making a diagnosis, confirming suspicions and
governing treatment.
The problem is that the CT scanner is being used too much and it is contributing to a public
health crisis. Studies estimate that 30% percent of CT scans are not needed and I
believe that is an underestimate. All those unneeded scans are creating exposure to a harmful, but invisible, toxin. If a newly discovered environmental toxin in our food or water was noted to cause almost enough cases of cancer to fill a baseball stadium every year it would be all over our televisions, newspapers and webpages. Should we not hold modern medicine to the same standard?
A few months ago my 6 year old nephew George fell about 12 feet and landed on the ground head first at a family party on rock hard pavement. He was rushed to the emergency room and
even though he was conscious and appeared well he was given a CT scan. The reason
for this was that George’s mechanism of injury was deemed “high risk” and therefore
the CT scan was indicated. His scan was normal and all the adults left the Emergency
Room feeling better that day, reassured that Georgie did not have bleeding inside his
brain. Georgie and his family will have to live with the increased risk of cancer but
overwhelming odds are he will not get cancer from his CT scan.
But George’s situation was black and white. George needed the scan because his fall
was high risk and the good outweighed the bad. When the situations are black and
white decisions are easy to make. When situations are grey things gets tricky. What
if instead of falling from 12 feet he fell from only 4 feet? And what if instead of
absorbing the blow only in his head Georgie had a second injury on his arm indicating
that it had absorbed some of the force of the fall? Georgie would have been in a grey
area under those circumstances. Physicians today who find themselves in those “grey
areas” are relying on CAT scanning to help them figure things out. It
reassures physicians and patients but the costs are tremendous: we are creating tens of
thousands of cancer patients per year. This is the definition of a public health
emergency.
Studies have been done and there are clear evidence based rules that tell doctors when
to use CAT scans to image heads, necks, abdomen and chests. Physicians should be
conscious of the harms of CT scan and the price of getting definite answers and try to
stick to these rules in the context of their own judgement.
The risk is one physicians must take at times, but unnecessary CAT scans are causing disease and we all took an oath to do no harm. When physicians minimize patient harm and rely on evidence based rules to form the backbone of their decision making and help them decide when to use the CT scan then they will be making decisions that benefit patients and truly doing no harm.
