How Safe Are Medical X-rays?

September 02, 2008

A patient recently came in to see me complaining of a headache of several days duration. Given the symptoms and duration in this particular patient, I decided to order a CT scan of the head to make sure he did not have a life-threatening condition. To my surprise, the patient expressed some resistance to the scan. Sometime, patients who are claustrophobic might express some concerns about undergoing the test. This patient, however, remarked, "Dr. Whyte, Do I really need it? Can’t CT scans cause cancer?"

In order to answer this question, it’s helpful to review medical imaging. X-rays allow us to peer inside the body and see everything from broken bones to pneumonia, but x-rays can involve exposure to radiation.

How concerned should you be about x-ray radiation exposure?

To begin, radiation is a type of energy that we are exposed to naturally- there are low levels of radiation in the air we breathe, in the food we eat, and in our own bodies. Because some radiation also comes from space, even living at a higher elevation in places like Denver exposes you to a slightly higher, but still very small, amount of radiation compared to someone at sea level.

An x-ray is a specific kind of radiation that can pass through tissue so that we can see things, such as bones and lungs, by the shadows and silhouettes the x-rays leave on film. Somewhat like taking a photograph, plain x-ray films give us a two-dimensional picture. Taking x-rays films from many different angles enables us to put together a three dimensional image using computers, which is what we call a CT scan, also know as a CAT scan.

Exactly how much radiation exposure is there from x-rays or CT scans?

A common yardstick for radiation exposure is the daily "background radiation" that we naturally are exposed to every day of our lives. Here are some rough comparisons:

• Flying cross-country~ a few days of background radiation
• Chest x-ray to look for pneumonia~ a couple of days of background radiation
• CT of the head to look for a stroke or tumor~ almost a year of background radiation
• CT of the abdomen to see if you have appendicitis~ a few years of background radiation

The important thing to notice is that x-ray and CT imaging have radiation exposure comparable to what we are exposed to day-to-day.

One concern is that large doses of radiation may increase the risk of certain kinds of cancer. However, the low doses of radiation used in x-ray and CT medical imaging carry much smaller risks, and this small risk needs to be weighed against the clear and very significant benefits, such as avoiding an unnecessary surgery, finding a stroke, or finding a broken bone that needs to be splinted.

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Watch a video demonstration of a CT Scan.

Flu Shot Season

September 21, 2007

Find out if you—and your family—should get it this year

It’s Fall! Time for football, apple-picking, and—for millions of Americans—a flu shot. According to the Centers for Disease Control (CDC), about 36,000 people in the US die each year from "the flu"—also called "influenza" by doctors—which is a respiratory illness caused by influenza viruses. So should you get a flu shot—the vaccine intended to prevent the infection—before the leaves change this season?

First, it helps to understand a bit more about influenza. The symptoms of influenza vary but typically include a combination of common cold-like symptoms (dry cough, sore throat, runny nose) and the sudden onset of fever, headache, extreme fatigue, and muscle aches. People with influenza are contagious even before they start to feel sick and can spread the infection just by coughing or sneezing near others.

For most patients, influenza is a self-limited illness—meaning the symptoms will go away in less than a week’s time. But for some, the infection can have serious consequences, such as pneumonia. These are the people who really need the influenza vaccine. If you fall into one of the following categories, then YOU should get a flu shot this season:

• adults 50 years of age or older
• children aged 6 months until their 5^th birthday
• pregnant women
• people who live in nursing homes or other long term care facilities
• people of any age with chronic medical conditions (including heart or lung conditions, asthma, diabetes, kidney disease, or HIV infection)
• people who live with or work with anyone who meets the above criteria OR with children less than 6 months old (who are too young to be vaccinated)

(source: CDC)

• Some people should NOT receive the influenza vaccine without first talking with a physician. They are:
• people who have a severe allergy to chicken eggs
• people who have had a severe reaction to the influenza vaccine in the past
• people who developed Guillain-Barre syndrome (a neurologic condition) within 6 weeks of receiving the flu vaccine previously
• children less than 6 months old
• people with a moderate to severe illness with fever, who should wait until their symptoms improve before getting the influenza vaccine

(source: CDC)

The influenza vaccine comes in two forms: injection and nasal-spray. The nasal-spray vaccine is only for individuals aged 2-49 years who are not pregnant and who are otherwise healthy.

You might ask, "If I had a flu shot last year, do I need it again this year?" The answer is, Yes! The vaccine is required yearly because the viruses that cause influenza can change slightly and because your body’s ability to fight the infection declines over the course of the year.

The influenza vaccine is the best way to prevent influenza this season if you or your family members are in one of the categories we discussed. And, for everyone, don’t forget a year-round infection-fighting strategy: wash your hands!

You can find out more information about influenza and the influenza vaccine at http://www.cdc.gov/flu/

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About Diabetes

September 10, 2007

Over 20 million people in the United States have diabetes.

One of the most important things you can do to decrease your risk of complications is to get your blood sugar under control.  Improved glucose control can help save your eyesight, your kidneys, and even your life.  But what exactly does “improved glucose control” mean?  How do you know when you’re doing it right?

One of the most important tests in diabetes care is the “hemoglobin A1C.”  This test tells how well you’ve been doing at controlling your diabetes over the past three months.  When blood sugar is high it causes changes in hemoglobin, a molecule that carries oxygen in your blood.  The new form of hemoglobin is called hemoglobin A1C.  The more hemoglobin A1C you have, the higher the number—and high numbers mean your blood sugar is out of control.  The American Diabetes Association says a safe A1C number in diabetes is 7.0.  People without diabetes usually have an A1C number less than 6. 

How do you get that number down?  You have to monitor your blood sugar daily.  If your blood sugars are pretty good but your A1C is still too high, you may need to check your postprandial glucose level.  That’s a fancy way of saying that you should check your blood sugar one to two hours after the start of a meal.  The reasons are convincing.  Not only does that postprandial glucose level contribute a lot to your A1C, it’s been shown that high blood glucose levels following meals is a risk factor for death!

If you check your levels after you eat, you will see firsthand the effects that different foods have on your blood sugar.  Maybe you’ll see that your blood sugar tends to be high after breakfast or that a large bowl of pasta may not be the best choice for lunch.  If you know this from checking your postprandial glucose level, you will be able to make better food choices in an effort to fix it.  Further, if you keep a log of your levels, you will be able to aid your doctor in adjusting your medication schedule.  The American Diabetes Association recommends aiming for a postprandial glucose level less than 180 mg/dl.

If your doctor hasn’t mentioned postprandial blood glucose monitoring, it may be because he or she doesn’t know the importance of it.  Information in medicine changes quickly and it can be difficult to keep up.  The next time you visit your doctor, ask about postprandial glucose monitoring. It is, without question, another way that you can help keep your diabetes in optimal control. 

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Nutrition Advice from Discovery Health Experts

Unfortunately, many of them will develop serious complications of the disease.  Diabetes is a major cause of heart attacks, blindness, and limb amputation.  If you have diabetes, are you doing all you can to prevent these from happening to you? 

Studying the Studies

June 14, 2007

More and more, patients are bringing in stacks of articles they have printed from the Internet. Some of my physician colleagues get irritated over this, since they do not have time to go over all these studies.  I have actually found it to be an opportunity to discuss with patients how to interpret what they learn online.  The old adage, "just 'cause it is printed, it doesn't mean it's true", also applies to the Internet: just cause you can Google it, doesn't mean that the studies are good.

I always encourage patients to search the Internet and read studies, but I also tell them to bring them in to discuss. In medical research, we refer to the "hierarchy of evidence."  Some types of studies are better than others.  You want to spend more time reading the articles that involve the best type of studies.

So what do you look for?  Here’s a general overview:

The best type of study is a randomized clinical trial.  Here, we test a drug or treatment by comparing two groups: one is called the experimental group and the other is the control group (this one is simply observed).  Usually, we like them to be double-blinded, meaning neither the doctor nor the patients knows whether they are receiving the drug or placebo.

A cohort study follows a group of people over time to determine which persons develop a disease.  These studies often give us information about various prevention strategies.  Cohort studies are better if they are prospective (outcome has not occurred yet) rather than retrospective (outcome has already occurred).

Case-control studies are typically retrospective: patients who have a disease are compared with those who do not.  We then study differences in these patients to determine causes of the disease.

A meta-anaylsis is a review of studies that collects and pools all the results.  These types of studies have become much more common.  The key is to look at the studies that were combined; remember "garbage in, garbage out."

If you're reading the actual study, look in the "Methods Section" and keep in mind the hierarchy of evidence.  No one expects you to be able to understand everything on a medical study, but do a little bit of "research on the research" and you'll become a more informed patient.

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