Weigh the risks

Weigh the risks I am writing in regards to the CT (computed tomography) scanner recently put into use in Whitehorse. Being a doctoral candidate in the field of diagnostic imaging, I found it to be an important and valuable step forward for health-care p

I am writing in regards to the CT (computed tomography) scanner recently put into use in Whitehorse.

Being a doctoral candidate in the field of diagnostic imaging, I found it to be an important and valuable step forward for health-care practice in the Yukon.

With that said, I recently visited Whitehorse to see family and friends, and was a bit alarmed at the frequency of individuals I encountered who said they had had one or multiple CT scans since it had been put into use.

Of course, my observations were based merely on anecdotal information, but I still left feeling a need to disseminate a little information on the radiation and risks involved with a CT scan, and the available alternatives.

I would first like to offer a disclaimer: There are many instances in which a CT scan is immensely relevant and helpful to diagnosis and treatment. If indicated and recommended by your physician, it is a valuable test in which the risks often outweigh the benefits.

I have myself had a CT scan to rule out appendicitis. Weighing the risks and benefits should certainly be part of any discussion with your physician, including before you receive a CT scan. The goal of this letter is simply to keep Yukoners informed going into such discussions, and assist them in asking questions.

The radiation risk of a single CT scan is certainly not negligible, although only over the past five years have studies been conducted to put this risk into context.

For example, comparisons have been made to the exposure and cancer incidence of individuals in Hiroshima, or relative to an X-ray scan. The level of radiation exposure depends on what area of the body is being scanned, and many other factors related to the patient’s physiology and scan parameters.

Ionizing radiation, as is used in an X-ray or CT scan, either directly affects DNA or indirectly through ion formation, which leads to increased cancer risk. The radiation risk is often listed by the ‘relevant organ dose’ in units of milli-Sieverts (mSv), based on the radiation absorbed per unit of mass. New parameters to minimize the effective radiation dose are increasingly being put into place, but have not yet significantly reduced risk.

As an example, a single chest X-ray has approximately 0.01 mSV, while an adult abdominal CT scan has a relevant organ dose of 10 mSv. Most individuals receive more than one scan in a single CT study, easily approximately 30-40 mSv. This translates to a lifetime risk of cancer of approximately 1/114 or 0.9 per cent for a woman who received one CT scan in her 20s, and less for older individuals and males.

Over the past four to five years, a series of studies has reported that very few patients are properly informed of the risks of a CT scan, and as many as 50 to 90 per cent of hospital physicians underestimate the radiation risk, although it is now part of most clinical screening protocols.

So, although CT scans may provide very valuable diagnostic information and should not be turned down if deemed important for determining diagnosis or to the course of treatment, it is also important to be informed of different imaging options in lieu of a CT scan. Even if these do not show anything, they may provide alternatives that would expose patients to relatively little or no radiation before proceeding to a CT scan.

X-ray has long been established as a useful and fast imaging method. Often, injuries, sinus problems, joint problems, etc., could be first visualized with an X-ray. Although with some radiation exposure, as mentioned, the amount is considerably less than through a CT scan.

Ultrasound or echocardiography is another valuable imaging method, which is an inexpensive and relatively accessible alternative to CT.

For example, evaluation of heart problems, such as murmurs, heart function and structure, and valve defects could be evaluated by echocardiography (heart ultrasound) without any risk of radiation exposure.

Magnetic Resonance Imaging (MRI) is a safe and comprehensive imaging method. As far as I know, this is unfortunately less accessible to Yukon patients, requiring a trip to Calgary or Vancouver. Still, in a nonemergency situation, MRI and cardiac MRI are valuable tools for assessing symptoms in many parts of the body, without any radiation exposure. MRI most often provides even more in-depth information about abnormalities of the tissue. (I should also disclose that my research focus is in the field of cardiac MRI, which presents some bias.)

I would like to restate that a CT scan may often be the best option, with the benefits outweighing the risks.

Still, it is important to maintain an open discussion with your physician about these options, and to be cognizant of the available alternatives.

Ultimately, the individual risk of a CT scan is not high; however, with increased radiation exposure in the population, this may present itself as a greater public health issue for the Yukon in the future.

In conclusion, if the required diagnostic information can be acquired using alternative tests, such options should be used.

Anna Schmidt


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