Pediatric Radiation Risk and CBCT
A 10-year-old boy is referred for a CBCT scan to evaluate an impacted maxillary canine. The parent is concerned about radiation exposure. The child has had multiple radiographs in the past. The clinician is considering a CBCT with a large field of view (FOV) to include the entire maxilla and mandible. The child is small for his age.
1. What are the radiation risks associated with CBCT in a pediatric patient, and how do they compare to conventional radiographs?
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Pediatric patients are more radiosensitive due to rapidly dividing cells and longer life expectancy. CBCT doses are higher than conventional radiographs but lower than medical CT. Effective dose for a large FOV CBCT can range from 50 to 500 µSv, compared to 5-50 µSv for a panoramic radiograph. The risk is stochastic (cancer induction) and deterministic (skin effects) but deterministic effects are rare at diagnostic doses. The ALARA principle (As Low As Reasonably Achievable) should be applied. The risk is justified if the diagnostic benefit outweighs the risk. In this case, the impacted canine may be assessed with a smaller FOV or conventional radiographs (panoramic and periapical) first. If CBCT is necessary, use the smallest FOV that covers the region of interest and pediatric exposure protocols (lower mA, kVp, and exposure time).
2. What strategies can be used to reduce the radiation dose while maintaining diagnostic image quality?
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Strategies include: collimation to the smallest FOV that includes the impacted canine and surrounding structures, reducing mA and kVp according to pediatric protocols, increasing voxel size (lower resolution) if fine detail is not required, using pulsed exposure rather than continuous, and limiting the number of scans. Also, shielding with lead apron and thyroid collar (though evidence for thyroid shielding in CBCT is debated). Justification of the exam: ensure that the CBCT will change management. Optimization of parameters: use the manufacturer's pediatric preset. Audit of doses. In this case, a small FOV focused on the maxilla may suffice, avoiding the mandible and reducing dose. If the canine position can be determined with a panoramic and periapical, CBCT may be avoided.