With increasing smoking history, the ADC maps showed progressive breakdown of the lung structure in all regions of the lungs. All smokers with a history greater than 18 pack-years (equivalent to one pack of cigarettes per day for 18 years) showed significant abnormalities compared to nonsmokers.
CT was performed after MRI, to allow comparison between the two modalities. Even though CT is the more established modality in the investigation of lung disease, it failed to show the same defects detected with MRI. Moreover, with the combination of MRI and hyperpolarized helium, the researchers were able to measure lung structures with 2½ times more precision than with CT, and 10 times more precision than with conventional MRI methods.
Age is a significant factor in the development of emphysema-like changes. The researchers found that, in general, the airspaces in the lungs enlarge with age. However, smoking compounds the problem. Dr. Fain and colleagues showed in a related study that these changes occur at a much slower rate in nonsmokers than in active smokers.
"On average, active smoking accelerates emphysema-like changes at about twice the normal rate found with aging," Dr. Fain explained.
In addition to early disease detection, hyperpolarized MRI can also be used to plan surgical therapies and to monitor patient response to drug therapies without the risks of exposure to CT-related radiation.
Dr. Fain believes that this new method of using polarized gases to study lung diseases will provide a clearer picture of the underlying mechanisms of poorly understood conditions like asthma and chronic pulmonary obstructive disease, leading to better treatments.