There are good reasons for this trend. CT scanning and nuclear imaging have revolutionized diagnosis and treatment, almost eliminating the need for once-common exploratory surgeries and many other invasive and potentially risky procedures. The benefits of these tests, when they're appropriate, far outweigh any radiation-associated cancer risks, and the risk from a single CT scan or nuclear imaging test is quite small.
But are we courting future public health problems? The radiation you get from x-ray, CT, and nuclear imaging is ionizing radiation — high-energy wavelengths or particles that penetrate tissue to reveal the body's internal organs and structures. Ionizing radiation can damage DNA, and although your cells repair most of the damage, they sometimes do the job imperfectly, leaving small areas of "misrepair. We're exposed to small doses of ionizing radiation from natural sources all the time — in particular, cosmic radiation, mainly from the sun, and radon, a radioactive gas that comes from the natural breakdown of uranium in soil, rock, water, and building materials.
How much of this so-called background radiation you are exposed to depends on many factors, including altitude and home ventilation. But the average is 3 millisieverts mSv per year. A millisievert is a measure of radiation exposure; see "Measuring radiation.
Exposure to ionizing radiation from natural or background sources hasn't changed since about , but Americans' total per capita radiation exposure has nearly doubled, and experts believe the main reason is increased use of medical imaging.
If you mention the measurement of radiation, many people will recall the classic Geiger counter with its crescendo of clicks. But Geiger counters detect only the intensity of radioactive emissions. Measuring their impact on human tissues and health is more difficult. Medical tests. Home Medical tests. CT scan. Actions for this page Listen Print.
Summary Read the full fact sheet. On this page. Medical issues to consider before a CT scan Before you have a CT scan: Tell the doctor if you are pregnant or think you may be pregnant. Another type of test may be recommended. Tell the doctor if you have allergies, diabetes, thyroid condition or renal kidney impairment. Tell the doctor if you experience claustrophobia fear of small spaces. The doctor may give you a mild sedative to help you relax during the procedure.
Tell the doctor about any implanted device you may have such as a pacemaker or medication pump, as metal objects may distort the images. Follow all the instructions you are given. Some CT scans require the use of contrast material to improve the image quality. The contrast material may be taken orally or by an intravenous injection or both.
You may have to go without food and drink for a certain length of time before the procedure. Your doctor will give you detailed instructions on how to prepare for the test and what to expect.
A very obese person may be too big for the circular hole of the CT machine. The doctor may advise another type of medical imaging or diagnostic test. CT scan procedure Generally, the procedure includes the following: You may be given a large drink to consume before the procedure. This drink is an oral contrast agent that helps to enhance pictures of the stomach, small intestines and bowel. Expert advice is to ignore the vast majority of those results because slight abnormalities seen on scans are very common but rarely harmful.
Yet many doctors find the urge to order follow-up tests irresistible. None of this had to happen. None of this has to happen. There are also no national standards for the training or certification of technologists professionals who operate the imaging machines.
Some states allow almost anyone to work the equipment. The government relies on three outside accrediting organizations—the American College of Radiology, the Intersocietal Accreditation Commission, and The Joint Commission—to ensure the safety of advanced imaging facilities. But each group has different quality and safety standards.
Your doctor owns a CT scanner or has a financial interest in an imaging center An in-office CT might seem convenient, but it carries an inherent financial conflict of interest.
And studies have found that physicians who own scanners or are part owners of radiology clinics use imaging substantially more than others. If your doctor owns a scanner, ask why you need the CT or whether another test might be an option.
And if he is sending you to a radiology clinic, ask whether he is financially affiliated with it. Those scans are often touted as a way to detect early signs of cancer and heart disease. But most scans—and up to 80 percent in older people—have at least one abnormality that shows up on the exam.
Almost all of the abnormalities are harmless, yet about one-third of patients are referred to follow-up imaging, according to a study. And whole-body CT scans expose you to much more radiation than regular CT scans.
One study determined that for every 1, year-old adults who have the exam, one will die of cancer as a result. Your dentist recommends a 3D dental shot The CT technique, called cone-beam CT, exposes children to about six times more radiation than traditional dental X-rays.
The American Dental Association says that children rarely need them before orthodontic procedures. And several studies have shown that for any given dose of radiation, children are three to four times more likely than adults to develop malignancies, in part because their cells are more sensitive to radiation. High-frequency sound waves sent through the body create echoes as they bounce off organs and tissues.
Echoes are then turned into real-time images called sonograms. Radiation exposure: none. Magnetic resonance imaging uses magnets and radio waves to create detailed images that can help spot cancers and soft-tissue problems. Patients are enclosed in the machine for 45 minutes to 2 hours before the image is captured. Uses low-dose X-rays to spot masses and mineral deposits that could indicate breast cancer.
Radiation exposure: low. The standard scan emits a broad beam that passes through the body before landing on film, casting shadowlike images. Fluoroscopy produces a continuous image, or X-ray movie. X-ray is excellent for bones. Radiation exposure: minimal to medium. Computed tomography uses a pencil-thin X-ray beam to create a series of images from multiple angles, which are then transferred to a computer, creating a 3D image that can be enlarged and rotated onscreen. Excellent for looking at soft tissue.
Radiation exposure: minimal to high. Positron emission tomography requires the patient to ingest a radioactive tracer, usually thru injection, that lands in cells, especially cancer cells. Radiation exposure: medium to high. Just one CT scan of the abdomen and pelvis equals about 10 millisieverts, more radiation than most residents of Fukushima, Japan, absorbed after the Fukushima Daiichi nuclear power plant accident in Doses are typical values for an average-sized adult.
For every 2, people exposed to 10 millisieverts of radiation from a ct scan, one will develop cancer, according to the Food and Drug Administration. The truth is we are all exposed to radiation every day of our lives, with no evidence that those low doses cause any long-term harm.
Areas that have higher background radiation levels e. If there is a cause and effect, it's simply too small to measure. And, because of increased research and updates in technology, less radiation also is used these days in medical imaging.
I can take two Tylenol for a headache and not worry about it being dangerous. But, if one Tylenol will get rid of my headache, it is prudent medicine to take a lower dose -- and that is what we want with radiation. In addition, radiologists are keenly aware that radiation doses will vary based on patient size, so children are given a child-size dose instead of the amount an adult would receive. If patients are unsure about getting a CT scan, they should ask their referring physician to explain the reasons it was requested.
Materials provided by Mayo Clinic.
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