Medical radiation: do we get too much exposure?

Resource Post for March

Are people exposed to too much radiation in the name of diagnostic medicine? I was at the dentist for a normal check up earlier this week. This was my first visit at this particular clinic and I was surprised that I had to undergo an X-ray of my whole jaw. There I was sitting in the dentist’s chair with a computer screen in front of me showing the X-ray pictures of my jaw and my teeth as the dentist explained to me in detail what I have and I don’t have. The check up was very thorough as Swiss check ups tend to be. Really nice. But was the X-ray really necessary?

Radiation exposure has been shown to be a risk factor for many types of cancer, including breast and thyroid cancer. Although medical devices usually use in low doses of radiation, these technologies are still pretty much unregulated. Currently, mammography is the only diagnostic method which is regulated by the US federal government.

Ionizing radiation and cardiac studies

In a recent science advisory, the American Heart Association (AHA) says “there are no data to support the use of cardiac computed tomography angiography (CCTA) in asymptomatic, low-risk patients, so the albeit-small risk of cancer from radiation currently outweighs the lack of any demonstrable benefit in such people.” The advisory was published in the AHA journal Circulation this month.

The advisory especially addressed diagnostics tests which uses ionizing radiation, namely:

• computed tomography (CT) scans
• fluoroscopy (e.g. an angiogram)
• radionuclide studies.

The AHA advisory also gives the following statistics:

• The collective dose of medical radiation exposures of the US population have increased by more than 700% between 1980 and 2006.
• CT scan use has grown by more than 10% every year and accounted for about 50% of the collective dose in 2006.
• About 65% of the collective CT dose is from studies of chest, abdomen, and pelvis.
• Cardiac CT scan accounted for 1.5% of the collective CT dose and this is expected to rise.
• Nuclear medicine research have increased by 5% each year and accounted for 25% of the 2006 collective medical radiation dose. 57% of these studies are used cardiac imaging and accounted for 85% of the radiation dose.

The advisory is in accordance with the results of the PROTECTION study, which stands for Prospective Multicenter Study on Radiation Dose Estimates of Cardiac CT Angiography in Daily Practice. The results of the study indicate that “there is great variation between centers in the amount of radiation emitted when a CCTA is performed and in the use of dose-saving strategies to reduce radiation exposure.”

Wellness scans

Many experts believe that diagnostic tests using radiation have potential benefits even in asymptomatic patients and play an important role in preventive medicine. CT scans are routinely performed nowadays as part of so-called “wellness check ups” which perform “body scans” as part of an annual check up as more and more clinics step up on disease prevention. The US Supreme Court Justice Ruth Bader Ginsburg was diagnosed in February with pancreatic cancer during a routine check up using computerized axial tomography (CAT). The tumor was at a very early stage and no overt symptoms were evident.

Many well-known clinics offer wellness scans is described as a non-invasive CT test from the collarbone to the pelvis and covers the heart, lungs and abdomen. The specific areas scanned in the abdomen are the kidneys, liver, gall bladder, aorta, adrenal glands, lymph nodes, spleen and other certain pelvic organs.”

The AHA panel of experts think that before any tests using ionizing radiation are to be ordered, the patient’s records should be closely examined to determine whether the test is absolutely necessary and whether the benefits justify the risk for cancer, especially in asymptomatic, low-risk patients. The attending physicians should also avoid duplications of any tests.

Non-ionizing radiation

In 2007, the European Commission announced that it is postponing the implementation of law which regulates health care workers’ exposure to electromagnetic fields (EMF). Directive 2004/40/EC was supposed to take effect in April 2008 and was aimed to protect workers against the occupational hazard of exposure to electromagnetic fields. However, the high limit values set by the said directive would inadvertently put a ban on the use of magnetic resonance imaging (MRI) in diagnostic medicine. Unlike the CT scan, MRI uses non-ionizing radiations or electromagnetic fields. The health risks to patients are said to be relatively less compared to ionizing radiation. However, the risk is there, both for patients and health care professionals. The EU decided to postpone the directive’s implementation till 2012 while awaiting for research evidence.

“MRI is currently the leading technique for detecting brain tumours and many other serious conditions. It allows doctors to help 8 million patients each year…[the EC] is well aware of the enormous benefits of MRI and of its immense value for public health.”

The EU is not the only one to be concerned about non-ionizing radiation and EMF. The International Commission on Non-Ionising Radiation Protection (ICNIRP) and the World Health Organisation (WHO) has also started to revise the current occupational limit values for electromagnetic fields.