Study Demonstrates Effects of Secondhand Smoke on COPD

Chengbo Wang, Ph.D. (left), presented the results of his study in a scientific poster at RSNA 2007.

A new MR imaging protocol has been used to visualize the damage secondhand cigarette smoke inflicts on nonsmokers.

Researchers at the University of Virginia School of Medicine in Charlottesville and the Children’s Hospital of Philadelphia used helium-3 (3He) diffusion MR imaging to study the lungs of 60 volunteers. Chengbo Wang, Ph.D., MR physicist in the Department of Radiology at The Children's Hospital, presented results at RSNA 2007, noting the team developed their technique to determine which nonsmoking patients either had, or showed, a tendency to develop chronic obstructive pulmonary disease (COPD). Fifteen to 30 percent of smokers develop COPD, according to Dr. Wang.

Dr. Wang described the challenge to develop a methodology that would be sensitive enough to pick up subtle changes in the lung tissue never before detectable. "For lung cancer and cardiovascular disease, there is some link with secondhand smoke," he said. "For COPD, there has been no research that could confirm this." Dr. Wang said he believes the team's early results confirm that secondhand smoke is a public health threat. Secondhand smoke is classified as a carcinogen by the Environmental Protection Agency and has been linked to heart disease, lung cancer and a number of respiratory illnesses including asthma and bronchitis.

A press conference Dr. Wang gave about his study was one of the best attended during RSNA 2007.

Changes in Small Airways, Alveolar Sacs Detected

Fifteen adult participants in Dr. Wang's study were current or former smokers. Forty-five people had never smoked and 22 of them had a high level of exposure to secondhand smoke.

To utilize the long-time-scale, global 3He diffusion MR imaging employed by the researchers, patients inhaled a specially prepared helium gas before imaging. The scanner then collected images showing the gas in the patients’ lung tissue. MR measured how far the helium atoms diffused inside the lungs during a 1.5 second breathhold. Using these measurements, researchers detected changes deep in the small airways and alveolar sacs of the lungs—areas that can be destroyed, develop holes or become enlarged after prolonged exposure to cigarette smoke.

The group identified lung damage consistent with emphysema by measuring the increased distance the helium atoms moved—that is, diffused into the lung parenchyma. Those measurements were translated into apparent diffusion coefficient (ADC) values, with increased ADC values indicating the helium atoms were able to travel farther, or diffuse into more parenchyma, during the measurement period.

Researchers found that 67 percent of the smokers and 27 percent of the nonsmokers who had high exposure to secondhand cigarette smoke had ADC values greater than 0.024, suggesting early lung damage was present, said Dr. Wang.

"We know the lung is a complex structure," he said. "We also know that lung function tests are not sensitive enough to pick up early damage. Currently the best method to detect COPD is CT. We noted that for some smokers, their lung function tests are just normal and healthy. In our pictures, the mean ADC didn't change a lot, but we could definitely see small, localized changes. The preliminary results indicate that the sensitivity of long-time-scale ADC measurements is clearly improved and is very helpful in catching early disease."

For the 27 percent of nonsmokers who had high ADC values, their early lung damage looked familiar to researchers, said Dr. Wang. "For some smokers, there is so much lung damage, we use CT and you can see the changes due to emphysema," Dr. Wang said. "We observed that around 30 percent of the study group showed similar changes and we hypothesized this kind of change may represent mild emphysema. We need more study to confirm this."

Study Spurred Changes for Participants

The results of the trial were eye-opening for some study subjects as well. Dr. Wang related the experience of one woman who participated. "When she looked at her pictures she was very surprised," he said. "She went home and asked her husband to quit smoking as soon as possible. Before, she thought the smoking only hurt him. Now it looks like the smoking also hurts her."

Dr. Wang said he hopes even this small study will help to inform public policy on smoking. "With secondhand smoke, it is clear there's damage to human health," he said. "I really think public policy needs to reflect this and restrict smoking in public spaces. If people want research to prove there's harm from secondhand smoke, I feel we have begun to provide it."

More and more states are considering tough anti-smoking laws. Statewide smoking bans went into effect in Minnesota on Oct. 1, 2007, and Illinois on Jan. 1, 2008.

Study of ATV Use by Children also Puts RSNA 2007 in Spotlight

Another popular RSNA 2007 press conference presented CT findings of many serious and some deadly injuries resulting from the use of all-terrain vehicles (ATVs) by children.

"The youngest patient in our series was 6 months 'young'—he was riding with his mother," said Chetan C. Shah, M.D., who presented "Imaging Findings in 500 Children Following All-Terrain Vehicle Accidents" during a scientific session. "Our youngest driver was 2 years 'young' and was driving a 'child-size' ATV." He added that 95 percent of children involved in ATV accidents were driving adult-sized ATVs. Another 2-year-old driver, found unconscious beside a flipped vehicle, had a severe brain hemorrhage that left her with permanent disability.

While ATVs can injure drivers of all ages, Dr. Shah maintained that use by children is intrinsically dangerous due to the instability of the vehicles and the children’s small size. While reducing the size and power of the vehicles and wearing helmets and protective clothing might limit injuries, he said, there remains the question of whether children should be riding ATVs at all.

The study included 345 boys and 155 girls admitted to Arkansas Children's Hospital following ATV accidents. Children ranged in age from 6 months to 19 years, with an average age of about 11 years. Among the CT-detected head injuries were 85 skull fractures, 66 cases of extra-axial hemorrhage and 59 brain injuries. Other injuries included 21 spine fractures, five spinal cord injuries and 36 pulmonary contusions. Femur fractures were the most common extremity fracture occurring in 208 children.

Injuries resulted in 12 traumatic amputations. Six fatalities were included in the study.

"If only a few parents could see these images, they might realize the danger and prevent their small children from using ATVs," said Dr. Shah.

The abstract for "Imaging Findings in 455 Children Following All-Terrain Vehicle Accidents" is available at RSNA2007.RSNA.org/rsna2007/V2007/conference/event_display.cfm?em_id=5009296.

Hyperpolarized Helium MRI
Researchers at the University of Virginia School of Medicine in Charlottesville and the Children’s Hospital of Philadelphia used helium-3 (³He) diffusion MR imaging to visualize the damage secondhand cigarette smoke inflicts on nonsmokers. Researchers were able to detect changes deep in the small airways and alveolar sacs of the lungs—areas that can be destroyed, develop holes or become enlarged after prolonged exposure to cigarette smoke.

Images courtesy of Chengbo Wang, Ph.D.