Microdose EOS Imaging: Just as Good, and Safer

Purpose: Children with scoliosis are exposed to significant lifetime radiation doses because of multiple imaging studies as part of their investigation and treatment. EOS scanning has been shown to significantly reduce overall radiation and cancer risk. To reduce radiation further, a microdose setting can be used on the EOS scanner. This study aimed to quantify the reduction in radiation dose and assess image quality compared to the standard EOS settings. Methods: A consecutive group of paediatric patients who received both a standard EOS dose and a microdose EOS scan for investigating their scoliosis within a 6-month period. The radiation doses were compared, and cancer risk was estimated using a validated risk calculator. Assessment of image quality was blindly evaluated by six surgeons, using a five-point visual analogue scale (VAS) between standard and microdose studies. Results: Twenty-five children who received both studies within a six month period were included, median age 13 (IQR 4). The total doses in the standard EOS group were 0.0895 mSv (additional lifetime cancer risk per study: 0.00197%); compared to the microdose group of 0.0167 mSv (additional lifetime cancer risk per study: 0.00037%) (p <.0001). Image quality VAS was not statistically different between settings (standard: 4.2, microdose 4.0) (p = 0.074). Conclusion: Microdose EOS resulted in a five-fold reduction in radiation dose compared to Standard dose EOS and a subsequent 532% decrease in lifetime cancer risk per study. This builds on the fact that Standard dose EOS already carries five times less radiation and cancer risk than plain films. Therefore, compared to traditional radiographs, using a microdose EOS would result in a 40-fold reduction in radiation dose, and a large lifetime reduction in iatrogenic cancer risk. Microdose EOS was found to be both safe and accurate for purpose. A larger study is needed to support these findings.