Reducing unnecessary CT scans and lowering the dosage of certain scans could significantly reduce the life-time cancer risk of children;
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A study examining X-ray computed tomography (CT) use in children has found that reducing unnecessary scans and lowering the doses for the highest-dose scans could lower the overall lifetime risk of future imaging-related cancers.
The 4 million CT scans of the most commonly imaged organs conducted in children each year could result in approximately 4,870 future cancers, the study found. Reducing the highest 25 percent of radiation doses could prevent 2,090 — or 43 percent — of these future cancers. By also eliminating unnecessary imaging, 3,020 — or 62 percent — of cancers could be prevented, said Diana Miglioretti, Dean's Professor in Biostatistics in the Department of Public Health Sciences at UC Davis Health System. "There are potential harms from CT, meaning that there is a cancer risk, albeit very small in individual children, so it is important to reduce this risk in two ways," Miglioretti said. "The first is to only do a CT when it is medically necessary, and use alternative imaging when possible. The second is to dose CT appropriately for children."
Miglioretti noted the CT use has increased dramatically because the technology is effective and offers greater convenience than other imaging methods that do not involve ionizing radiation. Radiation doses delivered by CT are 100 to 500 times higher than for conventional radiography, Miglioretti said. The retrospective study was conducted in children under 15 who were enrolled in seven integrated health-care systems. The researchers examined CT utilization data from six of the health-care systems between 1996 and 2010. Radiation dosage and estimated cancer risk were calculated by examining 744 random CTs of the head, abdomen/ pelvis, chest and spine conducted from 2001 through 2011 at five of the health systems. The researchers said exams from these regions of the body account for more than 95 percent of all CT scans.
Estimated lifetime attributable risks of cancers were calculated using the Biological Effects of Ionizing Radiation (BEIR) VII report for breast, colon, liver, lung, ovarian, prostate, stomach, thyroid, bladder, and uterine cancers and leukemia, and using models developed with similar methods for oral, esophageal, rectal, pancreatic, kidney and brain cancers, which account for as much as 85 percent of all U.S. cancer incidence.
The study found that CT use increased between 1996 and 2005. The researchers also found that patient radiation doses were highly variable for exams of the same anatomic region.
Miglioretti explained that children's organs are at an increased risk of cancer from CT scans because children still are growing and their cells are dividing rapidly. In addition, lifetime risk of cancer is greater among children because they are at the beginning of their lives — they have longer to live. She noted that physicians can reduce dosage amounts using a number of different strategies, including reducing scan length by focusing solely on the 'zone of interest' — the region requiring imaging. For example, when the zone of interest is the abdomen, physicians should avoid also scanning the pelvis. She said dosage guidelines for imaging pediatric patients should be followed closely.
"A smaller person needs a lower dose to come out of the machine to create an image of adequate quality for making a clinical diagnosis," Miglioretti said.
MEDICA.de; Source: University of California – Davis Health System