News


July 28, 2010

Asking questions and getting answers about CT scans and patient safety

Are computed tomography (CT) scans safe? When a recent article in the New England Journal of Medicine highlighted some concerns about the radiation exposure associated with CT scans, we asked radiologists in the Winnipeg Health Region to provide their perspective.

Specifically, radiologists were asked to respond to the article's suggestion that a person has a one in 80 chance, over their entire life span, of getting cancer as a result of a CT scan - a figure that, taken at face value, might give some people second thoughts on having a CT scan completed. As with all such figures, however, it is wiser to place things in the proper perspective.

One radiologist explained that he'd heard the risk was closer to one in 400, while another astutely made the point that a person's lifetime risk of getting cancer even without ever having a CT scan is one in five.

Further Reading
What's in place for maintenance?
What can you do as a patient?
What's Percipio?

"A key point is that there has never been any study showing that diagnostic radiology causes cancer - in fact, cancer mortality has generally decreased as radiology use increases," explains Dr. Iain Kirkpatrick. "That said, we are very conscious of dose. We of course must work under the assumption that medical X-ray use is potentially harmful."

Dr. Idris Elbakri, an Imaging Physicist with the Winnipeg Health Region, concurs. "It's good this issue has come to the forefront. Having said that, we are not using it in any way that's unsafe."

Every radiologist we spoke to suggested that the public asking questions is a healthy thing and that they welcome the chance to answer questions.

It's important, they said, to look at the context and note the American perspective. In Canada, radiologists or medical radiation technologists are typically, with a few exceptions, the ones doing imaging. Unlike in the US, CT scans in Canada are only available through referrals from a doctor (as opposed to in the US where individuals have the ability to schedule CT scans directly, sometimes from enterprising people who have set up shop with a CT scanner in a strip mall).

The data used in the New England Journal of Medicine also drew some added scrutiny from Winnipeg radiologists. For instance, the article acknowledges that the Food and Drug Administration (the agency responsible for protecting public health in the US) " . . . approves CT scanners but because it has no authority to oversee the way CT tests are used in clinical practice, it collects only limited data on routine doses . . . " That's not the Canadian way, they point out.

Along with Canadian standards (and safety procedures for radiology) outlined by Health Canada, the Canadian Association of Radiologists also has standards for performing and interpreting diagnostic CT scans.

"We are aware for the need provide excellent patient care while at the same time provide the most appropriate imaging with the lowest possible radiation dose," says Dr. Sandor Demeter, Diagnostic Imaging Medical Director for the Winnipeg Health Region. "We have initiated a number of strategies across the Winnipeg Health Region to achieve this."

The ALARA principle

ALARA stands for As Low As Reasonably Achievable. That means every Radiologist in the Region operates with the idea that their goal is to capture the required information in the best way while keeping risks to patients at a minimum.

"It requires the radiologist and x-ray technologist to operate the machinery to ensure every exposure is justified, that it is medically necessary and optimized thru the lowest dose," Dr. Elbakri. "We always strive to remind them and educate them about that."

The study

A detailed Manitoba study of CT doses and scanners is currently being conducted. Fifteen sites across the province are collecting data, which will be analyzed in the fall. A report with preliminary results is anticipated at that time.

Safety Code 35, published by Health Canada, references dosage levels for CT. Relatively new, these levels were published in 2008 and replaced previous guidelines identified by Health Canada.

"We have no reasons to believe our doses are any higher than those ranges in Safety Code 35 and the study will hopefully confirm that," says Dr. Elbakri.

"We are exposed to radiation by virtue of being alive. We need to keep that perspective - just by living we are exposed to radiation. Most medical radiation levels are less than what we're exposed to in the atmosphere," says Dr. Elbakri, "and there are enough controls in the process here to safeguard against machine error."

Physician education is also an integral part of the puzzle when it comes to discussing diagnostic imaging. That's why efforts such as grand rounds presentations explaining how to minimize radiation exposure to patients are important to help other physicians explain the benefits and risks to patients when choosing to send their patients for these types of diagnostic procedures.

Radiologists don't deal directly with the patient; they communicate primarily with the referring physician. For example, certain patients may advocate for certain tests against the recommendation of their physicians. Nuances like this may be unavailable to the radiologist, who may question the need for a specific test.

On the other hand, sometimes there is a particular bias towards a certain type of diagnostic imaging or a personal preference for one type of testing or a lack of awareness about the best diagnostic tool from the physician's perspective. That's where education and dialogue is important.

While recognizing that CT scans are an effective diagnostic tool, Dr. Edward Lyons, President of the Canadian Association of Radiologists, says that physicians should guard against repeating them too often and be sure to consider other tests that might give the information they require. "Both ultrasound and MRI have no radiation hazard," he says.

It's a matter of making the right diagnostic choice, says Dr. Blair Henderson, President of the Manitoba Association of Radiologists. "We pick the absolute best test to answer the question posed to us. In radiology there have been a number of research papers that have shown that patients and referring physicians typically underestimate the radiation exposure of CT. We act as the gatekeeper and advocates for patient safety. We will use the appropriate test or offer an alternate test of low or no radiation if we can."

Image Gently

Do You Need That Scan?

American College of Radiology on CT scans and cancer risk

American College of Radiology on the NEJM article

What's in place for maintenance?

An imaging physics group does extensive testing on scanners every year in the Winnipeg Health Region. "We check all doses, quality, and performance in a variety of ways. When we find something's out of specification, we let the clinic know and they take action with the service provider," says Dr. Elbakri. "This is not done from a maintenance perspective, but with a quality assurance mandate to do annual checks."

You should know . . .

  • Equipment is calibrated daily.

  • Site quality checks are done on CT scanners on a weekly and monthly basis.

  • Service providers do maintenance on CT scanners every six months.

Locally, the radiologist community is constantly monitoring doses and adjusting protocol to tone down radiation exposure to patients. "We want to minimize patient's exposure to radiation," explains Dr. Blair Henderson, President of the Manitoba Association of Radiologists. "If we use a very low dose, we run the risk of exposing the patient without getting a diagnostic image. We need to get a good enough image to answer the question but not too much so we're overexposing patients."

Did you know?

  • The Health Act regulates the use of medical equipment.

  • The Radiology Information System stores reports and facilitates scheduling.

  • The Picture Archive Communications and storage system takes images, stores them in a central location and makes them electronically available. This has been in place for the past five or six years and it has taken some time to get every facility in Manitoba on board. Within the year, this should be a reality and mean that if anyone has a scan in the province, a qualified professional with password access can see the results of previous examinations and actually view not only the report but the images themselves.

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What can you do as a patient?

  • Educate yourself. Reading information about your health, your body, your health care are all good ideas.

  • Make sure you are receiving information from credible, trusted sources. Not every website has accurate information to empower you in living a healthy life.

  • Alert your physician - radiologist if necessary - if you've had CT scans in the past, but particularly if you've had them within a specific period of time (for example, a year).

  • Provide enough details to your physician so the appropriate test can be requisitioned. If you're not telling your doctor all of the details they need to make an accurate assessment, you could be putting yourself at risk.

  • Ask if the dose is appropriate for the circumstances. There are different protocols for imaging children, for instance.

  • Never be afraid to ask, "Is this really necessary?" If it is, your doctor can explain why. If not, you can discuss an alternative.

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What's Percipio?

No it's not a Star Wars character. Percipio is medical software developed by Ontario-based company Medicalis that helps physicians order appropriate diagnostic imaging. From entering a patient's name and initial health concerns, a series of questions with drop down menus (and the ability to note specific observations) provides a methodical way to determine the appropriate diagnostic imaging for a physician to order.

When the test the physician is ordering isn't the best test for the circumstance, a screen with red lettering comes up and explains why. When the test the physician is ordering is appropriate, the software guides the physician to schedule the testing for the patient.

The radiology department at Children's Hospital is the only facility in the country currently using the software. The facility first tested the program in 2006. Physicians liked it and so it's been in place since the testing ended in 2007.

While generally physicians were ordering appropriately, the software provided insight about which physicians ordered certain tests most often and which physicians overrode the software's recommendations.

"We need to work with physicians and educate them about the most appropriate use of diagnostic imaging, why what we're suggesting is best," says Dr. Martin Reed, Head of Radiology at Children's Hospital, noting that, "compliance with the guidelines has improved over time."

"The goal is to get the appropriate test the first time," says Dr. Reed, who explains that if one diagnostic test doesn't reveal the necessary information that another may be required. "If a patient gets a CT and they needed an MRI, that's a waste of time and money. Reducing inappropriate orders will reduce wait times and save money."

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