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Medical Radiation
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Resource Description: 
The American Registry of Radiologic Technologists (ARRT) is the world’s largest credentialing organization that seeks to ensure high quality patient care in medical imaging, interventional procedures, and radiation therapy.
RadiologyInfo™ is the public information website developed and funded by the American College of Radiology (ACR) and the Radiological Society of North America (RSNA). It was established to inform and educate the public about radiologic procedures and the role of radiologists in healthcare, and to improve communications between physicians and their patients
WHO is the directing and coordinating authority for health within the United Nations system. It is responsible for providing leadership on global health matters, shaping the health research agenda, setting norms and standards, articulating evidence-based policy options, providing technical support to countries and monitoring and assessing health trends.
Episode number: 
803

(Source: The American Registry of Radiologic Technologists)  Medical Radiation--X rays are a form of radiant energy like light or radio waves. Just like light and radio waves, they can pass easily through some things and are absorbed by others. In the human body, some tissues are better at absorbing the radiation than others. The images made by x-ray beams come from these differences. Bone stops x rays efficiently, making them look white in an image; air, like in the lungs, does not absorb radiation much at all, and looks black in the image. Sometimes the images are still, like pictures from a camera, and sometimes they show movement, like a video camera.

Use of X ray technology

X-ray examinations provide valuable information about your health and play an important role in helping your doctor make an accurate diagnosis. In some cases, x rays are used to assist with the placement of tubes or other devices in the body or in other therapeutic procedures.

The examination most people think of is getting an x ray when they might have broken a bone. You often get an x ray of your chest when you have a bad cough that won’t go away. These images are called radiographs.

Fluoroscopy is the technique of using x rays to view the internal organs in motion. For example, it can be used to see if you are swallowing properly. It is often used in place of more invasive surgical procedures that take longer for recovery or to guide surgeons during a surgery procedure.

Use of CAT scan technology

Another very common procedure is a CT, or CAT scan. This type of exam lets physicians see detailed images of the organs in your body, looking at it in “slices.”

Radiation therapy uses x rays to treat cancers. The therapy team uses enough radiation, delivered just to the cancer, to kill the cancer cells, but sparing the normal tissue around it.

Perspective on overall radiation risk 

X rays have enough energy that, when absorbed by a tissue, they might do damage to the DNA in a cell. In high doses, this means that living tissue can be injured. The most conservative way of looking at it is to assume that any amount of radiation can cause injury, and the risk goes up as the amount of radiation absorbed goes up. Diagnostic imaging uses low doses of ionizing radiation, so the risk of an x ray examination is very, very small.

Because different tissues and organs have varying sensitivity to radiation exposure, the actual radiation risk from an x-ray procedure varies for different parts of the body. The term effective dose is used when referring to the radiation risk averaged over the entire body. It accounts for the relative sensitivities of the different tissues exposed. More importantly, it allows for roughly estimating the risk and comparing the dose from imaging procedures to other sources of exposure, such as natural background radiation.

The scientific unit for effective dose is the millisievert (mSv). Sometimes other units are used, such as Gray, rad and rem.

Non-medical sources of radiation

We are exposed to radiation from natural sources all the time, and this is called natural background radiation. It comes from cosmic radiation and radioactive materials that are found naturally in the soil and even in the food we eat. The average person in the U.S. receives an effective dose of about 3 mSv per year from these natural sources. These natural background doses vary throughout the country. People living in the plateaus of Colorado or New Mexico receive about 1.5 mSv more per year than those living near sea level.

The added dose from cosmic rays during a coast-to-coast round trip flight in a commercial airplane is about 0.03 mSv. Another source of radiation is radon. Like other sources of background radiation, exposure to radon varies widely from one part of the country to another, and even from one house to another.

Radiation and cancer risk

It is important to realize that there is no evidence that cancer rates or other effects are more common in areas with high natural background radiation rates compared to areas with low natural background rates. The only exception to this is when very high levels of radon are found and someone stays in that location for a long time.

To help explain the dose from an imaging examination, we often compare the dose to natural background radiation. We can say that the radiation exposure from one chest x ray is about the same as the amount of radiation exposure one receives from our natural surroundings over the course of 10 days.

How much radiation is required to take good care of my condition?

There is no simple answer to this question. The exposure it takes to image an arm to see if it’s broken is much less than that required for a CT scan of your abdomen to see if you have a cancer in your liver. Sometimes physicians will want to repeat an examination several times to see if you are responding as expected to your treatment.

It is just as bad not to use enough radiation as to use too much. If too little is used, the examination might have to be repeated to get it right, or the physician might miss a diagnosis. The job of the radiologic technologist is to use the correct amount every time.

Talk with your healthcare provider and your radiologist about the benefits of the suggested exam. Be sure to ask what you and your medical team expect to learn from your examination. Will decisions about your healthcare depend on the imaging study? If the results will not impact your future course of medical care or measure your progress from treatment, the examination is not necessary. Also, be sure to ask if the x ray, CT scan, or nuclear imaging is the best study, or would other non-radiation producing studies like ultrasound, magnetic resonance, or medical laboratory tests do as well?

Most of all, make sure that the people involved in the examination are properly trained and credentialed. It is these professionals who will make sure that the equipment is working properly and is used properly.

Overuse of radiation should be avoided, and your physician should prescribe only what is medically necessary to help make healthcare decisions, measure your treatment progress, or deliver therapeutic doses. Simple and clear conversations with your caregivers can help you understand why you may need an exam and which ones are best for your healthcare.

Source: The American Registry of Radiologic Technologists

 

Key Point 1

Medical imaging decisions are like other interventional decisions.  You have got to weigh the benefits and compare them to the risks, and the doctor and the patient have to make an informed decision based on the potential for good verses the potential for harm.

Key Point 2

Relying on imaging for diagnosis has consequences including radiation exposure, and the discovery of incidental findings that can set off a cascade of unnecessary, potentially risky medical procedures.  But if an exam is truly indicated and the benefit outweighs the risk, it should be done

Medline Plus

Medline Description: 

Interactive Medical Search logoConduct an off-site search for Medical Radiation from MedlinePlus.  These up-to-date search results are based on search terms specific to Second Opinion Key Points.

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