Next-gen paediatric imaging: ultra-low dose chest photon-counting CT approaching chest radiograph doses.

OBJECTIVE: Photon-counting detector (PCD) CT may reduce radiation dose while maintaining image quality, which is particularly promising for children due to their radiosensitivity. This feasibility study investigated whether an ultra-low dose CT (ULDCT) chest protocol on PCD CT, with a dose comparable to chest radiographs, could be developed to detect gross lung abnormalities in children. MATERIALS AND METHODS: This ethics-approved retrospective study consisted of two parts: (1) development of a ULDCT chest protocol using an anthropomorphic phantom and (2) qualitative evaluation of these scans performed in 24 consecutive patients (< 16 years) for various indications. Two paediatric radiologists assessed diagnostic quality for six chest pathologies using a 3-point Likert scale. Radiation dose metrics were extracted from a dose management system, and effective doses (ED) were calculated using age-appropriate conversion factors. Statistical analysis included mainly descriptive calculations. Doses were compared with routine chest radiography. RESULTS: The Lungman phantom was scanned using 5 different protocols. The optimal settings were identified as Sn100 kVp, 2 mAs and pitch 1.5, yielding an ED of 14 µSv. All paediatric scans were assessed as acceptable, but a preference for an increased dose protocol was given to rule out interstitial lung disease or bronchiectasis. The mean total ED from the localiser and ULDCT of the chest was 11.6 [IQR: 10.9-12.8] µSv compared to 8.2 [IQR: 6.2-13.6] µSv for standard chest radiography. CONCLUSION: Our PCD ULDCT chest protocol, approaching chest radiograph doses, is promising for (follow-up of) focal abnormalities and follow-up imaging of known chest pathology in children. KEY POINTS: Question Can the technique of photon-counting detector CT result in radiation dose reduction, while achieving adequate image quality? Findings An ultra-low dose CT chest protocol was developed with a comparable dose to a single chest radiograph. Relevance statement The ultra-low dose CT chest protocol is promising in the setting of (follow-up of known) focal chest abnormalities, long-term follow-up after congenital diaphragmatic hernia repair and follow-up of interstitial lung disease in children.