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The Risks of Low-Level Radiation
Written by Dr Raj Attariwala   

Japan and Chernobyl are not the problem.

After the recent disaster in Japan, radiation concerns were front and centre here in Canada, over 4,500 miles away from the source of the damaged nuclear plant in Fukushima. Nuclear disasters like this always garner headlines because we have a Hollywood-based notion that radiation exposure is going to turn people and animals into three-headed, grotesque monsters. The simple reality is that low-level radiation is always around us: from the granite in our countertops and radon gas in basements to cosmic radiation and solar flares from space.

In Vancouver, the average person receives a small amount of radiation every year from various sources. The radiation detected from Japan and Chernobyl registered barely a blip on province-wide charts. Man-made exposures to radiation are also common, from smoke detectors in our homes to air travel. In fact, the largest man-made exposure to radiation comes from life-saving medical devices such as x-rays, CT scans and radiotherapy treatments. So why is there so much concern about radiation? With increasingly high levels of exposure, radiation is known to cause transient ill effects, cancer or death. These ill effects predictably begin after the whole body has been exposed to high levels of radiation – meaning levels about 50 times higher than what we receive in the course of a year, but nowhere near the carcinogenic and fatal effects of atom bombs and nuclear disasters.

Low-Level Radiation Risks

A major current concern is with low-level radiation, either from a single exposure or from cumulative exposures. With low-level radiation, the cancer effects may occur anywhere from five to more than 20 years after the inciting event.

Diagnostic medical exposure to radiation is most prevalent from CT scanners. A CT scan of the lower spine can result in radiation exposures up to 15 times higher than that of an x-ray. The effects of CT radiation are difficult to predict, but are in the spotlight from recent events – including the effects of overexposure at a world recognized medical facility, and a multitude of medical journal articles raising the specter of cancer induction from this life-saving tool.

The concern about radiation from CT scanners has prompted the state of California to pass a new bill, which will go into effect January 2012, requiring hospitals to record the dose of radiation produced during a CT examination on every image of a study, and to chart this radiation dose in the patient’s permanent medical record. In addition, the American College of Radiology (ACR) and the Radiological Society of North America (RSNA) have campaigns to record radiation doses from CT studies much like immunization records. With their Image Gently and Image Wisely campaigns, these radiology organizations are recommending medical facilities and radiologists pledge to reduce radiation exposure and reliance on CT scans for diagnostic imaging studies. Reducing radiation exposure from CT scans is particularly important for females and young people who, over their lifetime, are more susceptible to cancer-causing effects from radiation. With guidance from the ACR, RSNA and soon California state law, vendors are being pushed to develop CT equipment with lower radiation, without loss of diagnostic accuracy.

Avoiding Diagnostic Radiation Exposure

Current alternatives to CT scans do exist for patients who are concerned about radiation exposure, including ultrasound and MRI. In a document posted on the Image Wisely website from Nov 2010, Dr Diego Martin writes that “for most clinical problems where CT is used to evaluate disease in the body, MRI provides an acceptable, or favorable alternative” and “MRI should be seen as a primary diagnostic method for a growing number of common indications, particularly for liver, pancreas, kidney, bowel, gynecological, prostatic and vascular diseases.” It is well known that MRI is superior to CT in evaluating the brain and spine. However, the downside of MRI or ultrasound is that they are more time consuming.

With the plethora of current medical literature surrounding CT radiation, more and more doctors are becoming aware of alternative forms of diagnostic imaging that don’t carry increased cancer risks. With advances in MRI technology and ongoing radiation concerns, it is predicted that in the not-too-distant future, CT scanners will be used mainly for trauma and lung tissue evaluation. This October, let’s all celebrate the 40th anniversary of the invention of the CT scanner and recognize that our diligence in recording radiation from necessary CT studies will allow future generations to predictably know the risks of its life-saving radiation exposure.

Dr Raj Attariwala -

Dr. Raj Attariwala, MD, PhD, is a radiologist, nuclear medicine physician and biomedical engineer. He is the director of nuclear medicine services for BC’s Northern Health, and a director at AIM Medical Imaging. www.aimmedicalimaging.com

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