New MRI technique detects secondhand smoke damage

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CHICAGO, Nov. 26—Helium-3 diffusion MRI can be used to detect structural damage to the lungs caused by secondhand cigarette smoke, according to study results presented today at the 93rd annual meeting of the Radiological Society of North America (RSNA).

The study, conducted by researchers at the University of Virginia School of Medicine in Charlottesville and The Children's Hospital in Philadelphia, used long-time-scale, global helium-3 diffusion MRI to study the lungs of 43 volunteers, including seven current and former smokers and 36 people who had never smoked. Eighteen of the non-smokers had a high level of exposure to secondhand smoke.

“It's long been hypothesized that prolonged exposure to secondhand smoke may cause physical damage to the lungs, but previous methods of analyzing lung changes were not sensitive enough to detect it,” said Chengbo Wang, PhD, MRI physicist in the department of radiology at The Children's Hospital.

Helium-3 diffusion MRI differs from a conventional MRI in that the patient inhales prepared helium gas prior to imaging, and the scanner is adjusted to collect images showing the helium gas in the tissue. In the study, MR measured how far the helium atoms moved, or diffused, inside the lungs during 1.5 seconds. Measurements were made into scores, apparent diffusion coefficient (ADC), values for each participant. An increased ADC value indicates that the helium atoms were able to travel farther during the measurement time.

"With this technique, we are able to assess lung structure on a microscopic level," Wang said.

Wang and his colleagues found that 57 percent of the smokers and 33 percent of the nonsmokers with high exposure to secondhand smoke had ADC values greater than 0.024, suggesting that early lung damage was present. In addition, 14 percent of smokers, 67 percent of high-exposure nonsmokers and 39 percent of low-exposure nonsmokers had ADC values below 0.0185.

The researchers concluded that only 15 to 30 percent of active smokers develop emphysema, while a larger fraction develops chronic bronchitis. A decrease in ADC values may reflect airway narrowing possibly from early chronic bronchitis, and an increase may be indicative of structural lung damage/sub-clinical emphysema.

Wang said the “findings suggest that breathing secondhand smoke can injure your lungs,” and he hopes their results will push legislation to prohibit public exposure.

T.A. Altes, MD, G.W. Miller, PhD, E.E. de Lange, MD, K. Ruppert, PhD, J.F. Mata, PhD, and G.D. Cates, PhD, are co-authors of the study.