MRIs demystified
Q: I'm scheduled for an MRI before I have knee-replacement surgery. How does it work, and do I have to get into one of those tubes? — Fred W., Waukesha, Wis.
A: Like the photographer in Antonioni's "Blow Up," MRIs take pictures of the unseen and make them visible. How? An MRI takes advantage of the fact that we are mostly made up of water (H2O — two parts hydrogen to one part oxygen).
Using a powerful magnetic field, the machine polarizes the protons in hydrogen molecules so they stand up and point in one direction — then sit back down. Imagine "the wave" rippling through the stadium seats at a baseball game. That's what happens to hydrogen molecules when an MRI is turned on.
And the incessant noise that can be so bothersome to someone inside the tube? That ping signals another dose of energy, starting another "wave" all over again. As the machine pings away, radio waves (not X-rays) organize the ups and downs, and they're assembled into a picture of your insides.
Everyone should have the option of getting an MRI before knee-replacement surgery. MRIs are also useful in diagnosing problems in the brain, heart and almost every other system. Doctors can see tissue and get a clearer picture of what is going on inside your body.
The standard machine is a metal tube that you slowly slide into; you have to stay very still while the image is formed. For many people, this can be disconcerting, so some opt for a sedative, anti-anxiety drug or even stress-reducing aromatherapy beforehand; we find breathing exercises and meditation to be extremely calming during the process.
There is also an Open Bore MRI; this model has a tube and gives a sharp image, but inside the tube there's a foot of space above your face, and sometimes you can have your head outside the tube.
So talk to your doc about what provides the best image for your pre-surgery consult and what you can handle. And give us a wave while you're in there!
Q: I've been hearing about re-vaccinations. Is it necessary to have them now that I am middle-aged? — Kathy P. Spokane, Wash.
A: In "Outbreak," Col. Sam Daniels (played by Dustin Hoffman) is a medical researcher at the U.S. Army Medical Research Institute who has to find a way to stop the spread of a lethal virus.
In real life, we YOU Docs want you to know there's a solution: vaccinations. More than 40,000 adults a year die from diseases they could avoid with a simple shot. (Avoiding these diseases also means less risk of heart attack and stroke.)
Here's the rundown on the vaccines you might need:
Flu injection, annual: Regular shot for anyone 6 months and older; high dose for 65 and older; and intradermal for those 18 to 64; a nasal spray live vaccine is for healthy people 2 to 49 (and not pregnant).
Tetanus, diphtheria and pertussis: Called Tdap — in lieu of a simple tetanus booster — everyone 19 to 65 needs a Tdap booster once and a tetanus booster every 10 years. Older than 65? Tdap or tetanus — it depends if you are in contact with an infant or not. Ask your doc.
Varicella (chickenpox): This vaccine is for everyone 19 and older if you haven't had the disease.
HPV (human papilloma virus): Recommended for women 19-26; for men 19-21 (and through 26, if your doctor recommends).
Zoster (shingles): Recommended for everyone 50 and older, with possible revaccination after 10 years.
Measles, mumps, rubella: Recommended once for everyone 19 to 55 if you haven't had the diseases.
Pneumococcal (pneumonia): There's now a vaccine approved for everyone 50 and older, with revaccination recommended every 10 years.
Meningococcal (meningitis): This vaccine, as well as those for hepatitis A and B, are advisable if a doctor thinks it's necessary.
Remember, more adults die of vaccine-preventable diseases in North America than from colorectal cancer, breast cancer, prostate cancer or car accidents.
The YOU Docs, Mehmet Oz, host of "The Dr. Oz Show," and Mike Roizen of Cleveland Clinic, are authors of "YOU: Losing Weight." To submit questions, go to RealAge.com.
