Matching the protocol to the clinical question in pediatric coronary CT - one size doesn't have to fit all

PURPOSE: To compare image quality and radiation dose between pediatric coronary CT protocols. METHODS: A retrospective observational study of pediatric coronary CT in children under 2 years old undergoing awake, non-sedated imaging in a pediatric cardiac surgical centre, comparing non-gated high-pitch dual source spiral (ng-FLASH); ECG-gated FLASH (FLASH); single-phase (30 ​% R-R) and multiphase (30-50 ​% R-R) sequential acquisition protocols. Dose metrics (DLP and CTDIvol) were collected and coronary visualisation assessed for the left mainstem (0 ​= ​not visible; 1 ​= ​visible), anterior descending, circumflex and right coronary arteries (0 ​= ​not visible; 1 ​= ​origin only; 2 ​= ​to mid-vessel; 3 ​= ​whole vessel). RESULTS: 128 consecutive studies were identified (84 ​ng-FLASH, 23 FLASH, 7 single-phase and 14 multi-phase sequential); median age was 3 months (range 1 day-17 months). Multi-phase sequential scans were the highest dose (median CTDI vol 1.66 ​mGy); cf. single-phase sequential 1.20 ​mGy (p ​= ​1.00); FLASH 0.57 ​mGy (p ​< ​0.001) and ng-FLASH 0.45 ​mGy (p ​< ​0.001). Multi-phase sequential scans had best image quality (median score 8, IQR 1.75) cf. single-phase sequential scans; 6, 5, p ​= ​0.95; FLASH 5, 5, p ​= ​0.15, and ng-FLASH 4, 3, p ​= ​0.001). Multi-phase acquisitions visualised coronaries to at least the mid-portion in 71.4 ​% (vs. 28.6 ​% single-phase sequential, 30.4 ​% FLASH and 13.1 ​% ng-FLASH). CONCLUSIONS: Coronary visualisation via CT in under-2 year olds can be achieved at a fraction of the dose expected from retrospective ECG gating, without anaesthesia. Where full coronary visualisation is not the primary aim of the examination, scan protocol can be adjusted accordingly. Stepwise increases in radiation exposure can be added according to level of coronary assessment required.