As a patient, it is common to have questions about the medical imaging procedures prescribed for you or your children. In fact, many people today wonder about the effect of radiation exposure when it comes to X-rays, CT scans and MRIs.
Decoding the Imaging Alphabet
Before you can understand the risks, it’s important to understand the purpose of each diagnostic tool. For instance, X-ray imaging, or radiography, is a relatively inexpensive form of imaging with very low levels of radiation exposure to patients, says Donna Hutchinson RT, CT, ARDMS, M, a sonographer at Mount Carmel New Albany.
“Most doctors start with an X-ray because it’s a good screening tool. If they see something on the X-ray that might require further imaging, they might refer the patient to get more advanced imaging (like a CT scan or an MRI),” Hutchinson explains. “It depends on what you are looking at. Both are very good tools.”
CT scans, or computed tomography, can help doctors detect everything from cancer to kidney stones. Although CT scans emit much more radiation than an X-ray, doctors order them because of improvements in diagnostic accuracy, greater availability and improved technology that reduces radiation exposure.
CT scans are good for looking at fractures and bony structures, says Director of Radiology Carl Hunlock, RTR, CT also from Mount Carmel New Albany.
In contrast to CTs, MRIs use strong magnets to allow for the computed generation of their images, says Dr. Allen Katz of Riverside Radiology and Interventional Associates, a board member of the Ohio Patient Safety Institute.
“MRI does not use (any type) of ionizing radiation; (that’s) one of its benefits, especially with younger patients,” he says.
Another benefit, says Katz, is “its outstanding soft tissue detail. This makes it very useful when evaluating injury to ligaments, tendons and menisci of the knee, for example.”
It also can provide unique information on the brain, chest, abdomen and pelvis. The disadvantages are long scan times, poor tolerance by claustrophobic patients and high cost, says Katz.
Radiation occurs naturally in our environment and has been a part of human life since the beginning. In fact, about half of the average U.S. citizen’s radiation exposure comes from natural sources, according to the United States Nuclear Regulatory Commission. The other half is mostly from diagnostic medical procedures, with CT accounting for the largest portion of this number. A small portion of radiation comes from consumer products such as tobacco, fertilizer, exit signs, luminous watches and smoke detectors.
CT scans, which use significantly more radiation than film X-rays, are the diagnostic tool currently receiving the most scrutiny. A typical CT of the head exposes a patient to 2 millisieverts (mSv, a measurement of the absorption of radiation by the human body), which is the equivalent of 100 chest X-rays or 243 days of background radiation from the environment, according to the Food and Drug Administration.
Medical experts are specifically concerned with how CT radiation affects children. Children are considerably more sensitive to radiation than adults because they have more rapidly dividing cells that can be exposed to low-level radiation, according to the FDA. In addition, they have a longer life expectancy than adults, so there is a bigger window during which damage from radiation can appear. As a result, a child’s risk for developing a radiation-related cancer can be several times higher compared to an adult exposed to an identical CT scan, according to the National Cancer Institute.
“Children have more delicate tissues ... so reducing the amount of radiation for standard procedures has been a very important factor in the development of our technology,” says Dr. Terry Barber, physician director for Nationwide Children’s Hospital’s offsite urgent care centers.
Fortunately, newer CT machines are calibrated to expose children to less radiation than ever before, Barber says. Even so, doctors may decide to forego CT scans in favor of other diagnostic imaging, such as ultrasound for abdominal trauma or appendicitis, when the equipment and trained personnel are available.
For children whose conditions require CT scans, especially a course of CTs over time, Barber says there are protocols to minimize risk, including limiting the number of scans, as well as the area scanned.
“We will minimize the field that we’re looking at … as opposed to doing an entire head CT scan if we’re just interested in the temporal lobe (of the brain),” Barber says. “So it’s not only the technique, but focusing on the problem and eliminating the extraneous radiation.”
CT is the largest contributor of medical radiation exposure in the United States. Betweeen 5 and 9 million CT exams are performed on U.S. children each year, according to the National Cancer Institute. Despite the number of benefits – including the detection of cancer or internal injuries – the obvious disadvantage is the inevitable radiation exposure and the chances that exposure can cause diseases such as cancer.
Although there is still some debate within the medical community about just how much long-term cancer risk CT scans carry, no form of radiation should be considered risk-free, according to the National Cancer Institute. As a result, medical professionals are taking steps to protect patients, especially children.
“While (CT) doses are relatively low, they are significantly higher than is generally used in radiography (or an X-ray),” Katz says.
“The radiation dose a person receives from diagnostic imaging, except for very rare accidents, is relatively small. For example, a CT of the abdomen is roughly equivalent to the radiation exposure received from the environment living two to three years in the United States.
Towards the other extreme, one routine mammogram exposes a woman to about the same amount of radiation she receives over one to two months going through her normal day. A radiograph (or X-ray) of the hand is even less exposure.”
So will this exposure cause people to get cancer? According to RadiologyInfo.org, a website run jointly by the American College of Radiology and the Radiological Society of North America, there is some evidence suggesting that the diagnostic levels of radiation.
A study from the National Cancer Institute estimated that of the 72 million CT scans done on Americans in 2007, there would be 29,000 future cancers related to those scans. That number is less than 1 percent of the people scanned. Additionally, the institute’s study indicates that the risk of cancer also depends on how many scans a person gets and which organs are exposed to radiation. Although each scan only has a small impact on a person’s long-term risk of cancer, that risk can build up over time with more scans and more radiation exposure; patients who receive regular scans for chronic problems would be more at risk.
For patients who require CT scans, Mount Carmel New Albany uses methods of reducing radiation exposure similar to those used at Nationwide Children’s.
These precautions include everything from following low-dose protocols, to implementing pediatric doses and shielding portions of the body that aren’t in the machines, Hutchinson says.
Making the Right Decision for You
In many cases, the benefits of a scan outweigh the risks.
“Physicians (wouldn’t) be ordering these tests if there wasn’t a huge benefit,” says Hutchinson. “At Mount Carmel New Albany all our scanners are using low-dose protocol. We also take a lot of precautions to ensure a very safe environment.”
There’s no doubt that CT scans can saves lives. For instance, if a person is involved in a serious car accident, a CT scan can be a quick and painless way to detect significant and sometimes critical internal injuries that may not be apparent otherwise. Even when test results are normal, information obtained via CT can prevent unnecessary surgery and lead to other diagnoses. Overall, the goal of any screening exam is to discover a disease at an early stage so it can successfully treated.
But when it comes to radiation, it’s good for patients to become aware of the issues, to talk with their doctors and to ask questions.
“Diagnostic imaging saves and improves lives every day by diagnosing treatable cancer, by identifying repairable injuries, characterizing infections to guide curative treatments and in many other ways,” Katz says. “It is important to weigh out these benefits against the potential risks of its use.”
So what should you ask if your doctor recommends a CT scan? Ask how a CT scan might contribute to your medical care and how it will benefit your treatment. You also might want to ask if it is the only option, especially if the CT scan is for your child. Together, you and your doctor can determine the best course of action.
“I encourage everyone to proactive about their health care,” Katz says. “It is the prerogative of the people to ask questions of health care personnel to their comfort level. Because children are especially sensitive to the effects of radiation, use of CT, in particular, comes with special considerations for children and pregnant women.”
Sherri M. Gordon is a contributing writer. Feedback welcome at email@example.com.