Radiation dose estimation for prospective and retrospective ECG-gated cardiac CT angiography in infants and small children using a 320-MDCT volume scanner.

OBJECTIVE: The purpose of this study is to determine patient dose estimates for clinical pediatric cardiac-gated CT angiography (CTA) protocols on a 320-MDCT volume scanner.
MATERIALS AND METHODS: Organ doses were measured using 20 metal oxide semiconductor field effect transistor (MOSFET) dosimeters. Radiation dose was estimated for volumetrically acquired clinical pediatric prospectively and retrospectively ECG-gated cardiac CTA protocols in 5-year-old and 1-year-old anthropomorphic phantoms on a 320-MDCT scanner. Simulated heart rates of 60 beats/min (5-year-old phantom) and 120 beats/min (1- and 5-year-old phantoms) were used. Effective doses (EDs) were calculated using average measured organ doses and International Commission on Radiological Protection 103 tissue-weighting factors. Dose-length product (DLP) was recorded for each examination and was used to develop dose conversion factors for pediatric cardiac examinations acquired with volume scan mode. DLP was also used to estimate ED according to recently published dose conversion factors for pediatric helical chest examinations. Repeated measures and paired Student t test analyses were performed.
RESULTS: For the 5-year-old phantom, at 60 beats/min, EDs ranged from 1.2 mSv for a prospectively gated examination to 4.5 mSv for a retrospectively gated examination. For the 5-year-old phantom, at 120 beats/min, EDs ranged from 3.0 mSv for a prospectively gated examination to 4.9 mSv for a retrospectively gated examination. For the 1-year-old phantom, at 120 beats/min, EDs ranged from 2.7 mSv for a prospectively gated examination to 4.5 mSv for a retrospectively gated examination.
CONCLUSION: EDs for 320-MDCT volumetrically acquired ECG-gated pediatric cardiac CTA are lower than those published for conventional 16- and 64-MDCT scanners.