For most women, there's very little risk from routine x-ray imaging such as mammography or dental x-rays. But many experts are concerned about an explosion in the use of higher radiation—dose tests, such as CT and nuclear imaging. Over 80 million CT scans are performed in the United States each year, compared with just three million in 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. That's where the sievert Sv and millisievert mSv come in. These units, the ones most commonly used in comparing imaging procedures, take into account the biological effect of radiation, which varies with the type of radiation and the vulnerability of the affected body tissue. So, people living in the higher parts of New Mexico and Colorado are exposed to more radiation per year about 1.
And a hour airline flight increases cosmic ray exposure by about 0. The amount of radiation exposure from an imaging test depends on the imaging test used and what part of the body is being tested. For instance:. Keep in mind that these are estimates for an average-sized adult.
Studies have found that the amount of radiation you get can vary a great deal. If you have concerns about the radiation you may get from a CT scan, PET scan, or any other imaging test that uses radiation, talk to your health care provider.
You may also want to know what you and your health care provider can expect to learn from it. The best advice at this time is to get only the imaging tests that are needed and try to limit your exposure to all forms of radiation.
For example, a lead apron can be used to protect parts of your chest or abdomen from getting radiation, and a lead collar known as a thyroid shield or thyroid collar can be used to protect your thyroid gland. A chest X-ray helps detect problems with your heart and lungs. The chest X-ray on the left is normal. The image on the right shows a mass in the right lung.
Some people worry that X-rays aren't safe because radiation exposure can cause cell mutations that may lead to cancer. The amount of radiation you're exposed to during an X-ray depends on the tissue or organ being examined. Sensitivity to the radiation depends on your age, with children being more sensitive than adults. Generally, however, radiation exposure from an X-ray is low, and the benefits from these tests far outweigh the risks. However, if you are pregnant or suspect that you may be pregnant, tell your doctor before having an X-ray.
Though the risk of most diagnostic X-rays to an unborn baby is small, your doctor may consider another imaging test, such as ultrasound. This X-ray using contrast reveals a kidney stone at the junction of the kidney and the tube that connects the kidney to the bladder ureter.
The X-ray tube is focused on the abdomen. X-rays will pass through the body and produce an image on the specialized plate below. Different types of X-rays require different preparations. Ask your doctor or nurse to provide you with specific instructions. In general, you undress whatever part of your body needs examination.
You may wear a gown during the exam, depending on which area is being X-rayed. You may also be asked to remove jewelry, eyeglasses and any metal objects because they can show up on an X-ray.
Before some types of X-rays, you're given a liquid called contrast medium. Contrast mediums, such as barium and iodine, help outline a specific area of your body on the X-ray image. You may swallow the contrast medium or receive it as an injection or an enema. X-rays are performed at doctors' offices, dentists' offices, emergency rooms and hospitals — wherever an X-ray machine is available.
The machine produces a safe level of radiation that passes through your body and records an image on a specialized plate. You can't feel an X-ray. A technologist positions your body to obtain the necessary views. He or she may use pillows or sandbags to help you hold the position. During the X-ray exposure, you remain still and sometimes hold your breath to avoid moving so that the image doesn't blur. An X-ray procedure may take just a few minutes for a simple X-ray or longer for more-involved procedures, such as those using a contrast medium.
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