Medical Radiation Dangers

Five questions to ask before receiving an imaging test

About 25 years ago, the average American’s exposure to radiation from medical imaging tests, such as X-rays, accounted for 15% of his/her total radiation exposure. The remainder came mostly from natural sources, such as soil and radon gas found in many rocks and minerals, and air travel (due primarily to exposure to cosmic radiation that is not blocked by the atmosphere).

Latest development: By 2006, medical radiation accounted for 48% of total radiation exposure, with a nearly 600% increase in the average per person medical dose — as measured by milli­sieverts (mSv), a standard unit of radiation risk.

What’s behind this huge increase in medical radiation? One of the primary causes is computed tomography (CT) scans. In the US, the number of these highly detailed medical scans increased from 3 million procedures in 1980 to 68.7 million in 2007.

Important new research finding: A study in the April 2009 issue of Radiology found that 7% of patients undergoing CT scans (for a variety of medical conditions) at Harvard University’s Brigham and Women’s Hospital received enough cumulative radiation from CT scans over a lifetime to increase their risk for cancer (all types) by 1% or more.

What you need to know…

KEY BENEFITS

While there are risks associated with imaging tests that utilize radiation, the potential benefits include…

Earlier diagnoses, leading to more effective treatments. Example: Mammography screening for breast cancer has led to increased survival rates.

More accurate diagnoses, resulting in better, more targeted treatments. Example: The clarity of the three-dimensional images produced by a CT scan can accurately pinpoint a tumor or blood clot, compared with the relative murkiness of an image produced by ultrasound (a nonradiation-producing medical test that creates images of internal structures through the use of high-frequency sound waves).

Faster tests, with less discomfort. Example: A CT scan takes seconds to perform, compared with 30 to 40 minutes for a magnetic resonance imaging (MRI) scan (a nonradiation-producing medical test that creates images of internal structures via the movements of atoms in a magnetic field).

Less invasive treatments. Example: When guided by the movie-like images produced by fluoroscopy, angiography (in which a catheter is used to clear a narrowed or blocked artery) is an effective alternative to open-heart bypass surgery, which involves grafting arteries or veins from another part of the body to a blocked coronary artery.

More effective treatments. Example: Targeted radiation therapy for cancer, guided by CT scans, is less likely than conventional radiation therapy to damage healthy tissue that is near the tumor.

QUESTIONS TO ASK

The potentially harmful effects of radiation exposure can accumulate over a lifetime. However, experts disagree — vehemently — about the actual health risk from exposure to low levels of radiation from medical imaging. Some say any exposure increases the risk for cancer — especially if it occurs during childhood, when cells are rapidly dividing and are more sensitive to the potentially damaging effects of radiation. Others believe that the potential benefits usually outweigh the risks.

To make use of the significant health benefits of medical imaging radiation, while doing everything possible to minimize risk, ask the following questions before receiving any radiological test, including dental X-rays…

1. Is this exam really necessary? By asking this question, you let your doctor know that you are concerned about your radiation exposure from the exam — which should cause the doctor to think twice about whether the imaging is really needed.

Your physician has the professional obligation to explain clearly why the radiological exam is needed — why ultrasound or an MRI scan is not appropriate for your medical condition and what purpose the exam serves in your diagnosis and treatment.

Useful: Find out if your radiological exam is warranted according to the “Appropriateness Criteria” developed by expert panels convened by the American College of Radiology (ACR) for 159 situations related to cardiac, gastrointestinal, musculoskeletal, neurological, urological, oncological and other conditions. To search the Appropriateness Criteria by condition and/or procedure, go to the ACR Web site at www.acr.org/ac.

Helpful: Keep a record of the radiological tests that you have received. This will help prevent duplication of tests.

2. Do I really need follow-up exams? Many physicians now do routine follow-ups with CT scans for conditions such as kidney stones and scoliosis. Ask your doctor if you can decrease the frequency of follow-up exams.

3. Am I receiving multiple scans with one test — if so, do I need them? For example, a typical “liver study” might involve three CT scans (an arterial phase, a venous phase and a delayed phase). Ask your doctor if the test you’re receiving involves multiple CT scans… if the multiple scans are really helping with your treatment… and if the number can be reduced.

4. Who will be performing the exam? The facility where the exam will be performed should be accredited by the ACR — which means minimum standards are being met for the quality of the equipment (delivering the proper doses) and training of the personnel (delivering imaging tests in the correct way). When making your appointment, ask if the facility is ACR accredited. If it isn’t, don’t have the exam there.

5. Who is recommending this exam? Historically, most medical imaging radiation was ordered by a radiologist in a radiology ­department. But in the last 15 years, many departments outside of radiology — such as cardiology and orthopedics — have acquired their own CT scanners. In fact, CT scanners are now so common that many physicians purchase them for their practices, citing the convenience to patients.

Troubling: Between 1998 and 2005, physicians who owned their CT scanners ordered three times more radiological tests, on average, than physicians without a financial stake in the exams.

What to do: If your doctor orders a scan using his/her own CT scanner, ask if the benefits of the test outweigh the radiation risks.

IMAGING TESTS WITH RADIATION

The four types of medical tests that use ionizing radiation…

X-rays. Beams of low-dose radiation are focused on an area of your body, producing two-dimensional, photograph-like images.

Radionuclide imaging. Example: Positron emission tomography (PET) scans. Radioactive substances are injected and detected by a scanner, which produces images that denote areas of increased metabolic activity (such as a tumor) or decreased activity (such as damaged heart muscle).

Fluoroscopy. A real-time, movie-like imaging test that uses X-rays.

Computed tomography (CT) scan, also called a CAT scan. An X-ray unit rotates around your body and produces detailed, three-dimensional images of your internal anatomy.

HOW MUCH RADIATION?

Besides radiological medical tests, other common sources­ of radiation include cosmic radiation from space. Examples of estimated radiation doses…*

*Based on averages for digital and analog equipment.

**Measured in millisieverts (mSv).

Source: www.radiologyinfo.org/en/safety/… www.ada.org/public/topics/xrays_faq.asp.