05/08/2011 06:40 pm ET Updated Jul 08, 2011

Why We Should Think Twice About Getting A CT Scan

There's an eerie video up on YouTube, shot by a Japanese journalist who ventured into the evacuation zone surrounding the Fukushima nuclear power plant, armed with a camera and a radiation meter. The video looks like b-roll footage from a low-budget zombie movie, with roving bands of stray dogs and a soundtrack of the radiation meter's increasingly frantic beeping.

Shortly after the earthquake that damaged the plant, the Japanese government evacuated residents from a more than 1,000 square mile zone. Last week, they raised the severity level of the crisis at Fukushima to a 7 out of 7, making it the worst nuclear disaster since the complete meltdown of the reactor at Chernobyl, in 1986. In its wake, worldwide fear of nuclear power spiked. The German government shut down seven of its 17 nuclear reactors, and plans to eliminate nuclear power by 2020. In the U.S., a Fox News Poll conducted in early April found that 83 percent of respondents thought a similar disaster could happen to an American nuclear plant.

People fear radiation for good reason. All ionizing radiation passes unimpeded through cells of the body, mutating or destroying DNA along the way. The danger level depends on the dose and the length of exposure. We're exposed to small amounts of radiation all the time -- from cosmic rays to the normal radioactive decay of soil, rocks and building materials. Even the granite in the U.S. Capitol Building emits low levels of radiation. These levels are harmless, but a high dose can kill, and prolonged or repeated moderate exposure can lead to cancer.

So why are we afraid of nuclear power, but not worried about the radiation in medical imaging tests, such as a CT scan? Here are a couple of scenarios to contemplate. Imagine waking up in the middle of the night, drenched in sweat, with an unfamiliar tightness in your chest. It could be a panic attack - you're certainly feeling panicky in the moment -- but maybe it's a heart attack, so you take yourself to the emergency room. Your tests look fine, but you're middle-aged with a gut and a smoking habit, so your doctor recommends you undergo a CT scan, just to be sure you don't have any dangerous plaque building up in your coronary arteries.

Now let's imagine a different situation. This time when you wake up in the middle of the night, it's an earthquake that jolts you out of bed, and you're a worker at the local nuclear power plant. You get a call from your supervisor, ordering you to suit up and get yourself down to the plant, which has been damaged by the quake and may be leaking radiation.

One choice seem like a no-brainer -- getting that CT scan -- while the other seems like a walk into the jaws of death, yet in both cases you would be exposed to similar amounts of radiation, about 15 millisieverts. (A millisievert is one of several ways to measure the dose of radiation.)

Other imaging tests deliver an even bigger blast. Inserting a stent, a little metal tube used to prop open a coronary artery, involves CT angiography, a kind of x-ray movie, and it can deliver up to 57 millisieverts during the course of one imaging test. That's the equivalent of standing at the power plant's gates for almost 5 hours during the peak of the crisis. 50 millisieverts is the annual limit for U.S. radiation workers. A cumulative dose of 100 millisieverts is known to increase the risk of cancer.

Radiation's harmful effects on the body are the same no matter the source, yet we see some kinds of radiation as bad and others as good. We request CT scans from doctors, but we'd have to be dragged kicking and screaming into the Fukushima evacuation zone.

Part of the reason for this is that the medical benefits of radiation can outweigh the harms. Before CT was used in medicine, beginning in the 1970s, a patient who suffered a blow to the head could be bleeding inside his brain, and there was no way to tell for sure without opening the skull, a surgery nobody wanted to do unless it was absolutely necessary. CT allowed doctors to peer through skin and bone and "see" soft tissue. Today, CT imaging is used to diagnose conditions ranging from brain bleeds to appendicitis to coronary artery disease.

Yet, for all the benefits CT imaging offers, it's still radiation, some in the American medical community worry radiological imaging is causing cancer. The number of CT scans performed has risen about 10 percent annually over the last 15 years, while the U.S. population has increased by only about 1 percent a year. Doctors performed over 70 million CT scans last year, or one scan for every fifth person, increasing our annual per-capita radiation dose by 600 percent since 1980. Obviously some people are not getting any scans, which means others are getting a much bigger dose of radiation. Radiation exposure falls heavily on particular patient sets - those with heart problems, and those with breasts.

This rapid expansion of CT is undoubtedly causing cancers. Recent studies suggest CT causes 29,000 cases of cancer a year, leading to 14,500 deaths. To put that in perspective, an equal number of people die from ovarian cancer each year. CT scanning is a real and significant cause of death.

In addition to the slowly accumulating danger of repeated radiation exposure, cases continue to come to light detailing overdoses from medical imaging errors. In 2009, more than 200 stroke patients at Cedars-Sinai Medical Center, in Los Angeles, began suffering from hair loss and skin redness after diagnostic head CT scans, possible signs of acute radiation sickness. An FDA investigation found that technicians had blasted the patients with eight times the appropriate dose of radiation. The estimated exposure was approximately 3000 to 4000 millisieverts, the equivalent of 50,000 X-rays. According to the U.S. Nuclear Regulatory Commission, a dose of 3500 millisieverts to the entire body is enough to kill a person.

The New York Times recently uncovered the case of Jacoby Roth, a 2½ year old boy who was brought to the emergency room in 2008 after falling out of bed. Over the next hour, the child was run through a CT scanner 151 times by a "rogue" radiology technician and suffered a massive radiation overdose of as much as 5300 millisieverts to his brain.

While the academic community still debates the health effects of low radiation levels, there is growing evidence that children are at higher risk. Their smaller bodies are more sensitive to radiation than those of adults, and they have longer to live, which means more time to develop cancer. Kids are routinely exposed to adult doses of radiation, which can be twice as harmful to a young body. A head CT can deliver almost 100 millisieverts to the infant skull and operators consistently fail to adjust scanners to lower pediatric settings.

Doctors are slowly waking up to the potential dangers posed by CT, but the number of scans continues to rise. Money is one reason. For every patient who passes through a scanner, the hospital makes money, helping them pay for their multi-million dollar machines. Some emergency physicians report being pressured by their hospitals to order CT scans. Doctors who own imaging centers are more likely to recommend scans than doctors who do not have a financial interest. In 2006, the latest year for which figures are available, 200,000 people submitted to a whole-body CT scan to look for early signs of several cancers. A whole-body CT delivers a whopping 25 millisieverts, and every credible medical group has condemned the practice.

Defensive medicine and demanding patients are two more compelling forces. Even when physicians know that a patient is better off without a scan, they worry about getting sued if the patient goes on to develop a condition that might have been spotted earlier. The cancer the patient may get down the road seems like a distant risk for the doctor. Patients also tend to focus on near-term dangers. Even if there's virtually no chance that your kid has suffered any harm after falling off the couch, a CT scan seems like the prudent decision, just to be sure he doesn't have a brain bleed. Our general obliviousness to the long-term risks of radiation makes it very difficult for physicians to convince us otherwise.

The medical device arms race has played a part. Hospitals regularly compete to have the most high-tech equipment, driven on by the importance placed on technology by the U.S. & World Report's hospital rankings. They advertise their newest gizmo to draw in patients, enthralled by the promise of safer, faster, (and the omnipotent and ambiguous) better. The assumption is made that the newest GE or Siemens' scanner provides an improvement in patient care. In the case of radiological imaging, as in an alarming amount of medicine more broadly, there are surprisingly few studies comparing patient outcomes between older, less dangerous techniques and the shiny new toy. It's not clear, for example, that the widespread use of abdominal CT scans has improved the diagnosis of appendicitis. Doctors don't know if the scans are helping to make patients any healthier, but continue to use them even though we know the increased levels of radiation they expose patients to can hurt and even kill them.

It took two concurrent acts of god -- an earthquake plus a tsunami -- to cause the crisis in Japan and expose the countryside to radiation levels deemed too dangerous to live with. In the U.S., all it takes is a poorly trained radiology technician, a persistent patient, or a defensive doctor. Unlike the handful of Japanese nuclear workers who have been exposed to sickening levels of radiation willingly as part of the known risks of their profession, American patients are exposed to equal risks unaware that they're often doing it for no good reason. As the ongoing disaster at the Fukushima power plant focuses the world's attention on the insidious dangers of radiation, maybe it's time to think just as hard about a CT scan as heading into the fallout zone of a nuclear disaster.