A research team led by Dr. Chetan Shah started with a group of 102 children who underwent both DR and 320-slice CT of the cervical spine. For the DR exams, radiation dose was calculated with an ionization chamber at a distance of 40 and 80 inches, with tube settings of 80, 100, and 120 kVp. Anteroposterior (AP) radiographs were performed at 40 inches, and lateral x-rays at 72 inches.
For the 320-detector-row CT exams, children younger than 5 years received scans with a wide-detector technique at 80 kVp, while older children were scanned at 100 or 120 kVp, with a few cases at 135 kVp, using either a helical or wide-detector mode.
Radiation dose calculations were derived from the CT scanner for both CT dose index (CTDI) and dose-length product (DLP), and DLP was converted to absorbed radiation dose using published conversion factors.
The researchers found that the average radiation dose for AP radiography was 0.035 mSv, compared with radiation doses for adult AP radiography as high as 0.12 mSv in the published literature. For lateral DR, the average dose was 0.004 mSv, compared with up to 0.02 mSv for adult DR.
Pediatric doses were similarly low for the wide-detector CT technique. The researchers found an average radiation dose of 0.87 mSv, compared with 8.68 mSv for conventional helical CT (p < 0.00001). Radiation dose was always less than 1 mSv for children younger than 5.
DR of the cervical spine results in lower radiation dose compared to film-screen radiography, while wide-detector CT of the cervical spine uses less than 1 mSv of radiation in children younger than 5, the researchers concluded.
