X-Ray, MRI, CT Scan : Radiation as Healer

by Food and Drug Administration (FDA)

(Page 3 of 3)

While MRI is a painless procedure, people who tend to feel claustrophobic may be uncomfortable inside the tunnel. For those people, anti-anxiety medicines are available, or they may choose a hospital or clinic that offers the less confining "open MRI" machine.

Sound Study

Ultrasound scanning isn't just for viewing a developing fetus, anymore. Originally used for this purpose, ultrasound today substitutes for conventional x-rays in the diagnosis of many conditions, commonly those involving the kidneys, bladder and uterus, the heart (called echocardiography), and the spleen, gallbladder and pancreas. However, ultrasound does not produce clear images of the lungs and other organs filled with gas or air.

With an ultrasound exam, a gel is spread over the skin covering the area of interest, and a "transducer" is moved back and forth to gather data. The transducer sends out high-frequency sound waves, far above the range of human hearing. When the waves hit the body part being studied, some are absorbed by tissues, and some are echoed back to a transducer. The machine measures the amount of sound reflected back, and displays an image called a sonogram on a monitor or on videotape or graph paper.

An ultrasound exam can take anywhere from 15 minutes to an hour.

While ultrasound is considered risk-free, FDA's Sacks says it still should be used only when medically warranted because "[t]here's no point in taking a chance for anything but a medical reason."

Helicopter or Zamboni

So, which diagnostic imaging technique is best? "Best for what? It really depends what you're looking for," says board-certified diagnostic radiologist Mark E. Klein, M.D. He likens the question to asking which mode of transportation is best: "In the mountains, you'd want a helicopter or four-wheel drive. On ice, you'd want a Zamboni." For example, he says, a skull x-ray to look for a brain lesion is useless, so the best choice might be a CT scan or MRI. For a broken arm, an x-ray would do the job and is preferred over an MRI.

X-ray, CT scanning, MRI, and ultrasound are among the most common noninvasive procedures (or minimally invasive, in some cases when a contrast agent is used), but the diagnostic options don't end there. Nuclear scanning, including two techniques called positron emission tomography (PET) and single photon emission computed tomography (SPECT), use radioactive substances introduced into the body to discern abnormal from normal body structures or evaluate the body's functioning. Other, sometimes riskier procedures require the insertion of tubes or instruments into the body.

A patient should know why the doctor is choosing a certain imaging technique, Sacks says. "The patient ought to feel secure about what's being done and understand the doctor's reasoning: 'What information does the doctor expect to get from this test?'"

During the test, too, the technician or radiologist can help the patient feel more secure. Julie (who asked that her last name not be used) says she didn't feel upset or panicky during her MRIs in 1997 to follow her uterine cancer. "The technicians were very careful to help me understand what to expect and what I would feel — 10 seconds of this, a minute of that, hold still for this length of time. I felt thoroughly prepared for it."

Her last MRI confirmed that she was "all clean" of cancer. "Even if the tests revealed bad news, I'm very thrilled they were there to give doctors a good view of my situation."

Wanda Diak's ovarian cancer has not been evident for almost three years. During her follow-up exams, she says, her doctor sometimes taps on her stomach to check for signs of recurrence. The method seemed primitive to Diak, but her doctor pointed out that before CT scans and other imaging, different sounds were all doctors had to clue them in to an abnormality.

"I think about someone tapping on your stomach rather than having this image that essentially slices you in half so you can see inside," Diak says. "It's like the caveman to the year 2000."

Radiation as Healer

While healthy people try to avoid extra doses of radiation, patients with many different kinds of cancer can turn the cell-destroying property of radiation to their benefit. According to the National Cancer Institute, at least half of cancer patients are treated with radiation therapy (sometimes called "radiotherapy") to cure the cancer or improve the quality of their lives by shrinking tumors and reducing symptoms.

Used alone or in combination with surgery, chemotherapy, or other treatments, radiotherapy aims to kill cancer cells with brief, high doses of radiation. In the most common type of radiation therapy, the external type, a machine directs the high-energy rays at the cancer cells.

Healthy cells that surround the cancer cells can be harmed, too, but the therapy works because cancer cells seem to be damaged more than noncancerous ones.

Side effects from radiation therapy can range from mild to serious, depending mostly on which part of the body is being treated and the dose of radiation used. The most common side effects include loss of appetite, fatigue, and skin changes.

About the Author

www.fda.gov
FDA is A United States government body that oversees medical devices, including contact lenses, intraocular lenses, excimer lasers and eyedrops. In the US, these products must be approved by the FDA before they can be marketed.