X-ray study scrutinizes radiation dose levels in children

Wide variations in patient dose may exist between and within hospitals in pediatric radiography examinations, and standardization in both equipment and techniques is lacking, according to a poster from researchers in Dublin presented at the RSNA meeting.

A team led by Dr. Kate Matthews from the School of Diagnostic Imaging, University College, explored whether ranges of dose levels for children are unnecessarily large. Tissue sensitivity is higher in children, leading to greater risk factors for certain cancers. Their small body size brings all radiosensitive organs close to or within the useful beam. For equal radiation exposure, children have a greater risk of delayed effects than adults because of their longer life expectancy, and almost all exposures are genetically significant.

"These factors result in pediatric risk coefficients for radiation detriment that are up to 10 times higher than those of adults," Matthews said. "Clearly, every attempt must be made to optimize standards within pediatric radiography."

Optimization requires doses to be as low as is reasonably achievable without a negative impact on the quality of the diagnostic image. Establishing diagnostic reference levels (DRLs) in pediatrics can be an initial step in the optimization process, allowing analysis of the potential for dose reduction. Because of variations in equipment and practice, DRLs may need to be established at a national rather than an international level, Matthews said.

The study found that age-specific radiation levels for the same examination vary markedly. Although differences between minimum and maximum values are substantial (up to a factor of 36), variations between the first and third quartile values are rarely greater than a factor of 4. Interquartile differences are less sensitive to aberrant dose outliers that can irrationally influence minimum:maximum ratios.

To address this problem, Matthews advocates the introduction of sensitive dose area product meters because they are user-friendly and widely available. Ultimately, the plan in Ireland is to develop age-specific DRLs for eight pediatric x-ray examinations including the pelvis, lumbar spine, and PA full spine.

A second poster from the Dublin group focuses on performance testing on x-ray equipment used for pediatric radiography. Lead author Tracey McCrudden, a research assistant, concluded that ongoing equipment monitoring takes place in the radiology department through regular quality assurance procedures and subjective assessments of equipment performance.