Mayo Clinic introduces low radiation CT scanner to reduce patients’ cancer risk
Post updated March 17, 2011
Computed tomography, also known as a CT or CAT scan, is one of the most common forms of diagnostic imaging. The scans are used to diagnose or monitor a wide range of medical illnesses including cancer and many heart conditions. It is not uncommon that cancer survivors get CT scans on a regular basis to check for signs of a recurrence. But the scans themselves expose the patient to levels of radiation which have become a source of concern to researchers over the past several years. Specifically, radiation exposure from CT scans has been linked to an increased risk of cancer. WCCO-TV medical reporter Dennis Douda announced yesterday that the Mayo Clinic is now using a new CT scanner that reduces the patient’s exposure to radiation, therefore decreasing the patient’s risk of cancer. Douda interviewed cardiac radiologist Eric Williamson who demonstrated the use of the Seimens Somatom Definition Flash dual-source CT scanner. As Williamson displayed an image retrieved from the scanner he said, “one of the most important things to realize about this image is that it was acquired with about one-tenth the dose of a conventional cardiac CT.”
A CT scan uses a series of images taken in a short period of time to create a picture of a particular part of the body. The imaging is considered to be more sophisticated than a typical x-ray. But since 1980, the average American’s radiation exposure has nearly doubled raising concern over it’s impact on a patient’s cancer risk. It is important to note however that currently no instances of cancer in a person have ever been linked directly to CT scans.
Experts agree that, regardless of risk, there are important benefits to the use of CT scans including the fact that the scans helps detect tumors, guide a biopsy, determine the stage of cancer and whether cancer has spread, and monitor the effectiveness of cancer treatment. In an article which reviews the risks and benefits of CT scans, CancerNet.com reminds readers that “a person diagnosed with cancer or suspected of having cancer can safely receive a CT scan because the benefits always outweigh the risks.” The site offers useful information about CT scans including a list of questions to ask your physician when a CT scan is recommended.
Questions to ask when a CT scan is recommended
* Why do I need a CT scan? (Why does my child need a CT scan?)
* Are there risks of having a CT scan?
* What are the risks of not having the test?
* Is a CT scan the best diagnostic examination for me (my child)? Or are there others we can substitute?
* Is the radiation dose of the CT scan the lowest possible dose that produces diagnostic images?
* Is the radiation dose based on my (my child’s) weight?
* Does the benefit of a CT scan outweigh its risks?
* Does this CT scan duplicate any previous tests?
I had received 3 CT scans in one day and now I am very concerned. What are my chances of getting cancer from this?
The bottom line is that the cancer risk from a medical CT scan is very low and, if the scans are clinically indicated, the medical benefit from such scans far outweighs any potential risk. But, here’s some additional information you may find of value.
Scientists estimate the risk of developing cancer from very low doses of radiation (such as from CT exams) by following the health of people exposed to small doses of radiation and comparing against the health of people not exposed to radiation. However, because the estimated increase in the number of cancers due to medical imaging exams is so low compared to the number of cancers in the general population, it would require following 5 million exposed persons and another 5 million unexposed persons over their entire lifetime to detect a clear increase in risk. And, the two groups would have to be similar in all other aspects (age, other health conditions, smoking history, etc.). Since we don’t have and are never likely to have such data, much smaller studies are used to estimate what the risk might be. Since scientists would prefer to be overly cautious rather than not cautious enough, we provide estimates of risk for low doses, even though at the dose levels associated with a CT scan, an increased risk of cancer has not been proven to exist. Data from various studies, all of which contain too few subjects and too many uncertainties, contradict each other, some finding no risk (or even benefit) and some finding a very small increase in risk.
However, because we can’t prove that there is no risk, medical exposures should be justified by the potential health benefit to the patient from the information gained, and the exam should be performed using the lowest reasonable doses. So if your exams were helpful in any way to your physician in managing your medical care, then the estimated radiation risk is negligible in comparison.
Still, patients and physicians want to have some idea of what the risk might be. We certainly know the risk is small! Otherwise it wouldn’t be so hard to demonstrate whether it does or doesn’t exist for these low doses. We may not know exactly how small, but we can give you a general idea using the following example.
The increase in risk associated with most CT procedures is generously considered to be about 0.05%. Therefore, the increase in risk for three CT scans within a single day would be about 0.15%. This increase is added to the risk of cancer in the general population, which is about 23%. That means that without the 3 CT scans, 23 out of 100 Americans die from cancer. If everyone had 3 CT scans, this might increase to 23.15 out of 100 Americans. So, you can see that the 3 CT scans make very little difference. You should also keep in mind that the information gained from those CT scans can help detect and manage cancers, as well as other serious medical conditions. That is, they may improve people’s health so that fewer than 23 out of 100 Americans die from cancer. In fact, since the availability of modern diagnostic and treatment technologies, like CT scans, the death rate from cancer continues to go down, even though the numbers of cancers that occur have stayed relatively the same.
In summary, stay focused on your health and make sure that any medical procedure you may be asked to undergo is warranted. And if one or more CTs are needed, be assured that the risk is very small and the diagnostic information is extremely valuable.
I went to the Dr. had a cat scan, had my eyes closed. Saw a white light flash in my eyes. The x-ray tech said, there was no white light. Can you tell me what that was.
Dr recommend i High resolution CT to diagnsis possible Bronchiectasis. would you comment?
Thanks,
John