Secondhand Smoke Damages Lungs
Modified MRI Detects Changes Suggestive of Emphysema Long Before Symptoms Occur
Nov. 26, 2007 (Chicago) -- For the first time, researchers say they have
evidence that long-term exposure to secondhand smoke can cause structural
damage in the lungs that is indicative of
Their study also suggests that the modified
magnetic resonance imaging (MRI) technique used to detect the lung damage
may be able to spot emphysema long before
The researchers used global helium-3 diffusion MRI to study the lungs of 13
current or former smokers and 45 people who had never smoked. Of the
nonsmokers, 22 had heavy exposure to secondhand smoke, meaning they lived with
a smoker or worked in a bar for at least a decade. None had symptoms of lung
The modified MRI detected signs of early lung damage in 67% of smokers and
27% of nonsmokers with heavy exposure to secondhand smoke, says researcher
Chengbo Wang, PhD, of the Children's Hospital of Philadelphia.
In contrast, only 4% of nonsmokers who had never smoked and had fewer than
10 years of exposure appeared to have signs of early lung damage, he says.
The research was presented here at the annual meeting of the Radiological
Society of North America (RSNA).
Modified MRI Detects Lung Damage
Wang tells WebMD that it's long been thought that prolonged exposure to
secondhand smoke can cause lung damage and emphysema, but doctors lacked a way
to prove it.
"Previous methods of detection weren't sensitive enough," he
Helium-3 diffusion MRI offers more detailed images of the lungs than
previous techniques, he says.
It works like this: first, helium gas is polarized with a laser; this makes
it more visible on MRI.
Then, while lying in a conventional MRI scanner, a person inhales the
energized helium. In just six seconds, the scanner collects images showing how
the helium gas distributes in the tiny air sacs called alveoli in the lung.
Prolonged exposure to cigarette smoke causes the walls of the air sacs to
break down and the air sacs to become bigger and bigger -- early signs of
emphysema, Wang says.
As a result, helium travels much further in people with enlarged air sacs
than in people with healthy alveoli, he explains.
"Using helium MRI, we were able to detect microscopic changes suggestive
of emphysema in smokers and people exposed to secondhand smoke," Wang
RSNA spokeswoman Katarzyna Macura, MD, PhD, of Johns Hopkins Medical
Institutions in Baltimore, tells WebMD that the modified MRI needs to be
studied in larger numbers of people before it's ready for prime time.
"Accessibility and cost are the two big issues that need to be
addressed," she says. "Before any recommendations can be made, we need
solid data and proof that what we are seeing [on the scan reflects lung changes
indicative of emphysema]."