Radiation Safety

What You Should Know about Medical Radiation Safety
Imaging helps guide physicians in the diagnosis and management of their patients. Some types of imaging exams use ionizing radiation. The following information is to help patients understand various issues and questions surrounding this topic.

What is Medical Radiation?
There are several different ways radiation can be used to help patients medically. Radiation can be used for imaging or for therapy. Diagnostic imaging techniques using radiation include X-rays, computed tomography (CT) scans and radionuclide (nuclear medicine) studies. Therapeutic techniques include radiation for the treatment of cancer or an overactive thyroid gland.

How much radiation is used in imaging exams?
We all are exposed to small amounts of radiation daily from soil, rocks, building materials, air, water, and cosmic radiation. This is called naturally occurring background radiation. The amount of exposure depends on where we live. For instance, people living in the high mountains of Colorado are exposed to more cosmic radiation than people who live at sea level.

Radiation can be measured in many ways. Measurements can be used to estimate the radiation dose deposited in the whole body or to an individual organ. Due to each patient’s distinct body size and shape, different X-ray settings must be used to accommodate the unique differences. Estimating doses for even the same type of study can be misleading and comparing estimated doses for different exams is confusing. One way of looking at doses from X-ray examinations is to compare effective radiation dose estimates from different sources using millisievert units (mSv).

Source	Estimated effective dose (mSv)
Natural background radiation	3 mSv/yr
Airline passenger (cross country)	0.04 mSv
Chest X-ray (single view)	up to 0.01 mSv
Chest X-ray (2 view)	up to .1 mSv
Head CT	up to 2 mSv
Chest CT	up to 3 mSv
Abdominal CT	up to 5 mSv

The radiation used in X-rays and CT scans has been compared to background radiation we are exposed to daily. This also is misleading as this refers to whole body dose which is not truly comparable to studies that image only a portion of the body. However, this comparison may be helpful in understanding relative radiation doses to the patient.

Radiation source	Days of background radiation
Background	1 day
Chest X-ray (single)	1 day
Head CT	up to 8 months
Abdominal CT	up to 20 months

What are the risks from medical radiation?
There is no conclusive evidence that radiation from diagnostic X-rays causes cancer. However, some studies of large populations exposed to radiation have demonstrated slight increases in cancer risk even at low levels of radiation exposure, particularly in children. Major national and international organizations responsible for evaluating radiation risks agree there is likely no low-dose radiation “threshold” for inducing cancers. To be safe, we should act as if low doses of radiation may cause harm.

The risk for radiation induced cancers should be evaluated against the statistical risk of developing cancer in the entire population. The overall risk of a cancer death over a person’s lifetime is estimated to be 20-25%. For every 1,000 children, 200-250 will eventually die of cancer if never exposed to medical radiation. The estimated increased risk of cancer over a person’s lifetime from a single CT scan is controversial but has been estimated to be a fraction of this risk (0.03- 0.05 %). These estimates for the population as a whole do not represent a direct risk to one child. Another way of assessing the relative risk of having a CT scan is to compare the theoretical risk of one abdominal CT scan to other risks. The estimated risk of one abdominal CT has been compared to:

Driving 7,500 miles (accident risk)
Motorcycling for 1,000 miles (accident risk)

Despite limitations of estimating radiation dose, this information shows that the risk of developing cancer related to a single CT scan is very small, but the available research indicates that there might be some risk and the risk may be cumulative.

How can we minimize radiation risk?
There are ways to ensure that you are exposed to the smallest amount of radiation possible during an imaging study.

Image when there is a clear medical benefit
Use the lowest amount of radiation for adequate imaging based on your size and shape
Image only the indicated area
Avoid multiple scans
Use alternative diagnostic studies (such as ultrasound or MRI) when possible

If my doctor requests a CT scan, should I let it be done?
As with any medical procedure, benefit of the exam should always outweigh any risk. CT scans are a very valuable imaging technique that can improve medical care and diagnose some illnesses that no other tests can. CT scans can help determine the best treatment options, avoid other tests or surgery, and improve health outcomes. It is important to remember that if you face a serious illness that requires a CT scan, you should have no reluctance about having the exam. The benefits often clearly outweigh the risks. If CT is the best test, ask if your imaging provider uses appropriate low-dose techniques to minimize radiation exposure.

How can I be sure that my imaging facility is using appropriate reduced radiation techniques?
Some facilities that perform CT scans on adults may not use radiation dose reduction techniques when scanning children. You won’t know unless you ask and it is reasonable and within your rights to ask. Your imaging provider should be able to provide you with information about how they reduce radiation doses. You should also ask if the facility is accredited in CT by the American College of Radiology.

What are the alternatives to CT?
CT scans may be the best way to get the imaging information needed to make clinical decisions about your care. At times, your doctor may decide it is safer to simply be observant of your health before committing to a CT scan. Waiting may be difficult for you and your family, but may result in the same outcome without exposing yourself to unnecessary radiation. Ultrasound and magnetic resonance imaging (MRI) are imaging techniques that do not use radiation. Sometimes these imaging methods can provide similar diagnostic information and can be useful alternatives. MRI, a long exam, may require sedation which carries its own risks. CT scans may be the only way to get the information needed to make clinical decisions about your care. You should ask your doctor and radiologist whether alternative exams are appropriate for your situation.

If I still have concerns regarding radiation exposure, whom should I talk to?
Initial discussions should begin with the physician who is requesting the exam. Medical professionals must balance the risks and benefits of performing the study. Your doctor and the radiologist (who is also a physician) can work together on decisions about which study is best to perform. If your doctor cannot answer your questions, radiology physicians can provide further information. The information contained in this website should not be used as a substitute for the medical care and advice of your physician. There may be variations in treatment that your medical professional may recommend based on individual facts and circumstances.

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