How many msv in a ct scan

Children are more sensitive to radiation than adults. Because of this, health care providers are careful to reduce radiation exposure to pediatric patients for imaging tests that use radiation. Still, parents can and should ask questions before any imaging tests are done. An English version for children can be found online at www. Radiation experts believe that if imaging tests do increase the risk of cancer, the increase in risk is likely to be very small.

Most studies on radiation and cancer risk have looked at people exposed to very high doses of radiation, such as uranium miners and atomic bomb survivors. The risk from low-level radiation exposure is not easy to calculate from these studies. X-rays allow the radiologist to see the structures in your body in very fine detail.

X-ray exams provide valuable information about your health and help your doctor make an accurate diagnosis. Your doctor may use x-rays to help place tubes or other devices in your body or to treat disease. When radiation passes through the body, some of it is absorbed. The x-rays that are not absorbed are used to create the image. The amount the patient absorbs contributes to the patient's radiation dose. Radiation that passes through the body does not contribute to this dose. The scientific unit of measurement for whole body radiation dose, called "effective dose," is the millisievert mSv.

Other radiation dose measurement units include rad, rem, roentgen, sievert, and gray. Doctors use "effective dose" when they talk about the risk of radiation to the entire body. Risk refers to possible side effects, such as the chance of developing a cancer later in life.

Effective dose considers how sensitive different tissues are to radiation. If you have an x-ray exam that includes tissues or organs that are more sensitive to radiation, your effective dose will be higher. Effective dose allows your doctor to evaluate your risk and compare it to common, everyday sources of exposure, such as natural background radiation. We are exposed to natural sources of radiation all the time.

According to recent estimates, the average person in the U. These natural "background doses" vary according to where you live. People living at high altitudes such as Colorado or New Mexico receive about 1. The quantity most relevant for assessing the risk of cancer detriment from a CT procedure is the "effective dose".

The unit of measurement for effective dose is millisieverts abbreviated mSv. Effective dose allows for comparison of the risk estimates associated with partial or whole-body radiation exposures. It also incorporates the different radiation sensitivities of the various organs in the body. Radiation dose from CT procedures varies from patient to patient. The particular radiation dose will depend on the size of the body part examined, the type of procedure, and the type of CT equipment and its operation.

Typical values cited for radiation dose should be considered as estimates that cannot be precisely associated with any individual patient, examination, or type of CT system. The actual dose from a procedure could be two or three times larger or smaller than the estimates. However, no comprehensive data is available to permit estimation of the extent of this practice and reducing the dose can have an adverse impact on the image quality produced.

Such reduced image quality may be acceptable in certain imaging applications. 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.

Taking these into account, millisieverts describe what's called the "equivalent dose. We've long known that children and teens who receive high doses of radiation to treat lymphoma or other cancers are more likely to develop additional cancers later in life.

But we have no clinical trials to guide our thinking about cancer risk from medical radiation in healthy adults. Most of what we know about the risks of ionizing radiation comes from long-term studies of people who survived the atomic bomb blasts at Hiroshima and Nagasaki.

These studies show a slightly but significantly increased risk of cancer in those exposed to the blasts, including a group of 25, Hiroshima survivors who received less than 50 mSv of radiation — an amount you might get from three or more CT scans. See "Imaging procedures and their approximate effective radiation doses. The atomic blast isn't a perfect model for exposure to medical radiation, because the bomb released its radiation all at once, while the doses from medical imaging are smaller and spread over time.

Still, most experts believe that can be almost as harmful as getting an equivalent dose all at once. Source: Mettler FA, et al. Most of the increased exposure in the United States is due to CT scanning and nuclear imaging, which require larger radiation doses than traditional x-rays.