Dose Reduction in Pediatric CT: A Rational Approach

TLDR

To determine size‑dependent technique factors for pediatric CT using physically measured objective data. The study used 10–32 cm phantom cylinders scanned on a multi‑detector CT scanner, measured noise, dose, and contrast across 80–140 kVp and 10–300 mAs, and fitted the data to compute size‑dependent mAs values that preserve CNR. The computed size‑dependent mAs values reduced abdominal doses to 64 %, 29 %, and 9 % of adult levels for 25, 20, and 15 cm phantoms while maintaining CNR, and reduced head doses to 57 % and 37 % of adult values for 15‑ and 13‑cm heads.

Abstract

To determine size-dependent technique factors for pediatric computed tomography (CT) by using physically measured objective data.Six phantom cylinders (10-32 cm in diameter) were scanned with a clinical multi-detector row CT scanner. CT noise was statistically characterized for CT technique factors from 80 to 140 kVp and from 10 to 300 mAs. Dose measurements were performed with each phantom. Dilute iodine and tissue contrast were determined with computer calculations validated with measured data. The dose, noise, and contrast data were computer fit, and pediatric CT technique factors (milliampere seconds) necessary to maintain the contrast-to-noise ratio (CNR) were computed.As compared with that in a reference cylindric adult abdomen of 28 cm in diameter, CNR was maintained at a constant level in pediatric patients of 25, 20, and 15 cm in diameter, respectively, when milliampere second values of 0.557, 0.196, and 0.054 of the adult milliampere second values were used. The corresponding doses were reduced to 0.642, 0.287, and 0.090 of the 28-cm-diameter adult dose, respectively. CT techniques for examination of pediatric heads measuring 15 and 13 cm, respectively, can involve the use of milliampere second values of 0.572 and 0.366 of those used for examination of a standard 17-cm-diameter adult head.CT technique charts for pediatric abdominal and head examinations were produced on the basis of physically measured data; use of these tables will enable pediatric radiation dose to be reduced while CNR is preserved.