Ct scans how many are safe

A handful of studies published in the past decade have rekindled concerns. Researchers at the National Cancer Institute estimate that 29, future cancer cases could be attributed to the 72 million CT scans performed in the country in That increase is equivalent to about 2 percent of the total 1. A study of medical centers in the San Francisco Bay Area also calculated an elevated risk: one extra case of cancer for every to 2, routine chest CT exams.

The reliability of such predictions depends, of course, on how scientists measure the underlying link between radiation and cancer in the first place. In fact, most estimates of the excess cancer risk from CT scans over the past several decades rely largely on a potentially misleading data set: cancer rates among the long-term survivors of the atomic bomb blasts in World War II.

About 25, atomic bomb survivors were exposed to relatively low doses of radiation comparable to between one and three CT scans. The number of cancer cases that developed over the rest of their lives is not, however, large enough to provide the necessary statistical power to reliably predict the cancer risk associated with CT scans in the general population today.

Given these difficulties, as well as renewed concerns about radiation levels and the lack of mandatory standards for safe CT exposure in contrast to such procedures as mammography , a dozen groups of investigators around the world have decided to reevaluate the risk of CT radiation based on more complete evidence. A growing number of clinicians and medical associations are not waiting for definitive results about health risks and have already begun figuring out how to reduce radiation levels.

Two radiologists at Massachusetts General Hospital, for example, think that they can decrease the x-ray dosage of at least one common type of CT scan by 75 percent without significantly reducing image quality. Likewise, a few medical associations are trying to limit superfluous imaging and prevent clinicians from using too much radiation when CT scanning is necessary.

For obvious ethical reasons, researchers cannot irradiate people solely to estimate the cancer risk of CT. So scientists turned to data about survivors of the atomic bombs dropped on Hiroshima and Nagasaki in August Between , and , people died during the detonations and in the months following them.

Most individuals within one kilometer of the bombings perished from acute radiation poisoning, falling debris or fires that erupted in the immediate aftermath of the attack. Some people within 2. A sievert is an international unit for measuring the effects of different kinds of radiation on living tissue: 1 Sv of gamma rays causes the same amount of tissue damage as 1 Sv of x-rays.

It is also important to note that, illnesses affecting older patients are more likely to require CT scans compared with illnesses affecting children. For more information, see Radiation Risk and Age. Studies show that the risk of cancer from CT scans is extremely low. Sometimes, your health condition will require an imaging exam that uses ionizing radiation. If you have concerns, talk to your doctor about the need for and importance of the exam.

CT is a proven, lifesaving imaging technology. It allows the physician to see inside the body. For the past 15 to 20 years, CT has helped guide treatment in ways we previously never thought possible. More importantly, it helps the physician determine if no treatment is necessary.

A CT scan should never be withheld from a child or adult who has a medical condition where the scan could provide important healthcare information. It may save the patient's life. The question you should ask is: "What should be done regarding my healthcare and diagnostic imaging tests?

Keep a record of your imaging history. So until we know more, you will want to keep your exposure to medical radiation as low as possible. You can do that in several ways, including these:. Discuss any high-dose diagnostic imaging with your clinician. If you need a CT or nuclear scan to treat or diagnose a medical condition, the benefits usually outweigh the risks. Still, if your clinician has ordered a CT, it's reasonable to ask what difference the result will make in how your condition is managed; for example, will it save you an invasive procedure?

Keep track of your x-ray history. It won't be completely accurate because different machines deliver different amounts of radiation, and because the dose you absorb depends on your size, your weight, and the part of the body targeted by the x-ray. But you and your clinician will get a ballpark estimate of your exposure.

Consider a lower-dose radiation test. If your clinician recommends a CT or nuclear medicine scan, ask if another technique would work, such as a lower-dose x-ray or a test that uses no radiation, such as ultrasound which uses high-frequency sound waves or MRI which relies on magnetic energy.

Consider less-frequent testing. If you're getting regular CT scans for a chronic condition, ask your clinician if it's possible to increase the time between scans. And if you feel the CT scans aren't helping, discuss whether you might take a different approach, such as lower-dose imaging or observation without imaging.

Don't seek out scans. The radiographer will operate the scanner from the next room. While the scan is taking place, you'll be able to hear and speak to them through an intercom. While each scan is taken, you'll need to lie very still and breathe normally. This ensures that the scan images aren't blurred. You may be asked to breathe in, breathe out, or hold your breath at certain points.

You shouldn't experience any after-effects from a CT scan and can usually go home soon afterwards. You can eat and drink, go to work and drive as normal.

If a contrast was used, you may be advised to wait in the hospital for up to an hour to make sure you don't have a reaction to it. The contrast is normally completely harmless and will pass out of your body in your urine.

Your scan results won't usually be available immediately. A computer will need to process the information from your scan, which will then be analysed by a radiologist a specialist in interpreting images of the body. After analysing the images, the radiologist will write a report and send it to the doctor who referred you for the scan so they can discuss the results with you.

This normally takes a few days or weeks.