Comparison of Image Quality and Radiation Dose between High-Pitch Mode and Low-Pitch Mode Spiral Chest CT in Small Uncooperative Children: The Effect of Respiratory Rate

Objectives: To compare image quality and radiation dose between high-pitch mode (HPM) and low-pitch mode (LPM) CT in young children. Materials and methods: Forty-seven children (mean age 35.6 months; range, 0–126 months) underwent 49 CT examinations in HPM or LPM and were divided into high or low respiratory rate (RR) groups. A qualitative image quality was compared between the two modes. The volume CT dose index (CTDI_vol) and dose-length product (DLP) were evaluated from the dose reports, and effective doses were assessed using a paediatric phantom. Results: Image quality was generally better for HPM than LPM (diagnostic acceptance score, 4.00 vs. 3.46, P = 0.004); the difference was more prominent in the high RR group (4.00 vs. 3.22, P = 0.001). However, there was no significant difference in the low RR group. The mean DLP value was higher in HPM than LPM (29.48 mGy · cm vs. 23.46 mGy · cm, P = 0.022), while CTDI_vol was not significantly different. The total effective radiation dose was 26 % higher in HPM than LPM (1.82 mSv vs. 1.44 mSv). Conclusions: LPM can be considered for paediatric lung evaluation in young children with low RRs to reduce radiation dose while maintaining favourable image quality. Key Points: • Radiation exposure is higher onhigh-pitch “Flash spiral mode” than onlow-pitch “X-CARE mode”. • “Flash spiral mode” generally showed better image quality than “X-CARE mode”. • Difference in image quality was more prominent in the high RR group. • There was no difference in image quality in the low RR group. • “X-CARE mode” should be considered in a limited population with low RRs.