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RSNA 2007 Reporter’s Notebook Editor’s Note: This article was prepared from media materials released by the Radiological Society of North America at RSNA 2007 last month. Radiation and Pregnancy:
Exposure Doubled in Last Decade “While performing CT exams during pregnancy is still uncommon, we found that pregnant women are being recommended for CT more often over the last 10 years,” said Elizabeth Lazarus, MD, assistant professor of diagnostic imaging at the Warren Alpert School of Medicine at Brown University in Providence, R.I. The investigators found that from 1997 to 2006, the number of imaging studies performed on pregnant women increased by 121%. “Through medical imaging examinations, we are exposing pregnant women to twice the amount of radiation as we did 10 years ago,” Lazarus said. “Overall, the levels of radiation to which we are exposing pregnant women are low, but they do carry a slight risk of harm to the developing fetus.” The researchers conducted a retrospective review of CT, plain film x-ray, and nuclear medicine studies performed at Brown to determine how often these imaging exams were utilized in pregnant women and estimate the resulting radiation dose to the fetus. The greatest increases were in the number of CT exams, which deliver more radiation than many other radiologic procedures. An abdominal CT exposes the patient to a radiation amount more than twice that of an x-ray of the lower gastrointestinal tract. An abdominal ultrasound exam does not expose the patient to ionizing radiation. CT is not routinely used in pregnancy, but pregnant women may undergo CT to detect suspected life-threatening conditions such as bleeding in the brain, blood clots in the lungs, or appendicitis. Since CT exposes the developing fetus to radiation, concerns are often raised regarding overuse. Approximately 75% of the CT scans analyzed in the study were performed in areas of the mother’s body separate from the uterus, so the fetus was not exposed to any direct radiation. However, even low levels of radiation have been shown to carry a small risk of harm to a developing fetus. The researchers evaluated 5,235 examinations on 3,249 patients. During the 10 years of the study, the number of patients imaged per year increased from 231 to 447, and the number of exams per year increased from 325 to 730. This represented an 89% increase in patients and a 121% increase in examinations over the course of the study. During the same 10 years, the number of deliveries only increased from 8,661 to 9,261, a 7% rise. Use of plain-film x-rays increased an average of 7% per year, and the number of nuclear medicine examinations rose by approximately 12% annually. CT examinations increased by approximately 25% per year. The average estimated fetal radiation exposure for CT was 0.69 rads, compared with 0.04 rads for nuclear medicine and 0.0015 rads for plain film x-rays. Other studies have shown that the use of high-tech modalities such as CT and MRI has increased in all patient populations throughout the United States. According to Lazarus, some of this increase is due to the development of new imaging techniques to better diagnose abnormalities, and some is due to motivation by hospitals and insurers to make fast diagnoses to shorten hospital stays and improve patient care. “I want to assure patients that CT can be a safe, effective test for pregnant patients,” Lazarus said. “However, there are alternatives that should at least be explored. Pregnant patients should ask their doctors about other imaging or diagnostic tests that may not expose the fetus to radiation.” ATVs and Children: A Dangerous
Ride “Our experience shows that children’s use of ATVs is dangerous and should be restricted,” said Chetan C. Shah, MBBS, a radiology fellow at the University of Arkansas for Medical Sciences and Arkansas Children’s Hospital in Little Rock. ATVs—motorized vehicles with large, low-pressure tires designed for off-highway use—can weigh up to 600 pounds and travel up to 75 miles per hour. While the American Academy of Pediatrics recommends that children under the age of 16 be prohibited from operating ATVs, no laws are in place in most states. ATV accidents are seldom reported because the vehicles are usually unlicensed and typically operated off-road or on private land. According to the Consumer Product Safety Commission, ATV-related injuries in children under the age of 16 more than doubled from 1995 to 2005, with 40,400 children treated in hospital emergency departments nationwide in 2005. This figure represents nearly one third of all ATV-related injuries treated that year. Child fatalities resulting from ATV accidents have also nearly doubled since 1995 with 120 reported deaths in 2005. ATV-associated injuries can be caused by crashes, rollovers, ejections, or disregard of simple safety precautions. But according to Shah, ATV use by children is intrinsically dangerous because of the vehicles’ instability and the children’s small size. The study included 500 consecutive children admitted to Arkansas Children’s Hospital following ATV accidents. The children ranged in age from six months to 19 years (mean age 11.5 years) and included 345 boys and 155 girls. Head injuries included 85 skull fractures, 66 cases of hemorrhage, and 59 brain injuries. Spinal injuries included 21 spine fractures and five spinal cord injuries. Lung injuries were present in 36 children. Injuries to the spleen, liver, kidneys, or pancreas were found in 70 children. Extremity fractures occurred in 208 children, with broken legs being the most common. There were 12 amputations, including nine partial foot amputations, one upper limb amputation, and one below-knee amputation. There were six fatalities and several cases of long-term disabilities. The fatalities represent only the children who died at the hospital, not those who died at the accident site. “The youngest patient in our series was a 6-month-old infant who was riding with his mother. His thigh bone was fractured,” Shah said. “Other patients included a 2-year-old who was driving a ‘child-size’ ATV and had traumatic amputation of four toes, and another 2-year-old driver who was found unconscious beside a flipped ATV. She had a severe brain hemorrhage that left her with permanent disability,” he said. Imaging the Danger of
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, an MR physicist in the radiology department at The Children’s Hospital of Philadelphia (CHOP). Cheng presented work from CHOP and University of Virginia School of Medicine in Charlottesville at RSNA 2007 last month. Wang and colleagues 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, 18 of whom had a high level of exposure to secondhand smoke. Helium-3 diffusion MRI differs from conventional MRI in that the patient inhales a specially prepared helium gas prior to imaging, and the scanner is adjusted to collect images showing this helium gas in tissue. MR measures how far the helium atoms move, or diffuse, inside the lungs during a specific time period: 1.5 seconds in this study. Using this method, radiologists and physicists can detect changes deep in the small airways and sacs in the lungs, which can break down, become enlarged, and develop holes after prolonged exposure to cigarette smoke. Helium-3 diffusion MRI identifies this damage by measuring the increased distance the helium atoms move. In recent years, secondhand smoke has emerged as a public health threat. It has been classified as a carcinogen by the Environmental Protection Agency and has been linked to heart disease, lung cancer, and a number of respiratory ailments, including asthma and chronic bronchitis. Children are particularly susceptible to the harmful effects of secondhand smoke. For the study, measurements were translated into scores called apparent diffusion coefficient (ADC) values for each of the participants. An increased ADC value indicates that the helium atoms were able to travel farther during the measurement time. Fifty-seven percent of the smokers and 33% 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% of smokers, 67% of high-exposure nonsmokers, and 39% of low-exposure nonsmokers had ADC values below 0.0185. Relatively low ADC values in adults are a possible indication of a developing respiratory problem, such as chronic bronchitis or asthma. “These findings suggest that breathing secondhand smoke can injure your lungs,” Wang said. “Since legislation to limit public exposure to secondhand smoke is still being considered in many states, we hope that our work can be used to add momentum to the drive to pass such legislation.” Exploring a Possible Link
Between Ethnicity and Mammography “Limited understanding of mammography still exists across different ethnic and socioeconomic groups,” said Nazia F. Jafri, MD, a medical intern at Mount Auburn Hospital in Boston. “Increased community outreach and education targeted at minority and underserved women may lead to better breast cancer prognoses in these groups.” Breast cancer incidence rates tend to be lower among minority women than among Caucasian women, but mortality rates are higher. According to the Department of Health and Human Services, African American women between the ages of 35 and 44 have a breast cancer death rate more than double the rate for Caucasian women in the same age group. Hispanic women in the United States are 20% more likely to be diagnosed with late-stage breast cancer than Caucasian women. While a number of factors may contribute to these statistics, the researchers sought to determine if ethnic or socioeconomic background held any sway over women’s beliefs or opinions regarding breast cancer screening for early detection. For the study, the researchers surveyed 1,011 women of various educational, ethnic, and socioeconomic backgrounds who underwent mammography screening at Boston University Medical Center. The survey asked women questions about their understanding of mammography and their preferences regarding call-back after a suspicious finding on a screening mammogram. The results showed that differences in ethnic background appear to influence women’s preferences regarding the trade-off between recall and earlier detection of cancer. Caucasian women strongly preferred recall given the possibility of earlier detection of cancer, compared with black (African American, Caribbean, and Haitian) and Hispanic women. Also, nearly one third of black and Hispanic women thought mammography would detect more cancers than it actually does. When asked if they would continue routine screening mammography after a false-positive result, 76% of Caucasian women said they would, compared with only 56% of black women and 48% of Hispanic women. “Women’s healthcare decisions and adherence to routine health screenings are affected by cultural factors, educational background, and access to medical care,” said the study’s principal investigator Priscilla J. Slanetz, MD, MPH, associate professor of radiology at Boston University Medical Center. “Our study shows that we need to improve breast health education among minority and underserved women.” Jafri suggested that further research is necessary to address the underlying factors that influence a woman’s decision to comply with screening mammography and to seek appropriate follow-up care. “Mammography does save lives, but only when cancer is detected early,” Slanetz said. “Most recalls are for benign causes and should not deter further screening.”
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