Pediatric photon-counting chest CT enables iodinated contrast dose reduction with preserved image quality

Photon-counting detector (PCD) CT allows for reduced intravenous iodinated contrast dosing with preserved or improved image quality across anatomical regions as compared to conventional energy-integrating detector (EID) CT in adults. However, there is limited evidence to support this in pediatric CT, particularly for pediatric chest CT.

To compare image quality of photon-counting detector (PCD) chest CT with energy-integrating detector (EID) CT at varying iodinated contrast doses in pediatric patients.

This retrospective observational study included 60 contrast-enhanced chest CT studies in pediatric patients. The cohort included three groups: 20 PCD CT scans with a 1.5 mL/kg weight-based iodinated contrast dose, 20 EID CT scans with a 1.5 mL/kg dose, and 20 EID CT scans with a 2.0 mL/kg dose. Image noise, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) were assessed through region-of-interest measurement of Hounsfield units (HU) and standard deviation (SD). Assessed locations were the lung parenchyma, thoracic aorta, main pulmonary artery, left ventricle cavity, subcutaneous tissue, and pectoralis muscle. Blinded review by three pediatric radiologists assessed overall contrast enhancement, soft tissue delineation, and streak artifact from dense contrast using 5-point Likert scales (1 - excellent to 5 - non-diagnostic). Group comparisons were analyzed using Wilcoxon signed-rank, Chi-square, and Kruskal-Wallis tests.

Twenty patients were included for each group (60 patients total). Compared to equivalent-contrast dose EID CT at 1.5 mL/kg, PCD CT showed higher left ventricle cavity SNR (21.6 [IQR 16.3-25.1] vs 16.2 [IQR 12.3-19.3], P = 0.05) and CNR (16.0 [IQR 11.3-19.5] vs 10.3 [8.8-13.7] P = 0.05), and lower image noise in pectoralis muscle (P = 0.04) and subcutaneous fat (P < 0.01). Furthermore, objective image quality on PCD CT demonstrated improvements in lung parenchyma noise, SNR, and CNR, as well as subcutaneous fat SNR and CNR (all P < 0.01) compared with both equivalent (1.5 mL/kg) and standard (2.0 mL/kg) contrast dosing in EID CT. No significant differences between PCD CT and EID CT were observed with other objective measures of image quality. Subjective assessments favored PCD CT for overall contrast enhancement to EID CT at equivalent (1.5 mL/kg) contrast dosing (median 1, IQR 1-1 vs median 2, IQR 1-5, P = 0.02) and soft tissue delineation compared with EID CT with higher (2.0 mL/kg) contrast dosing (median 1, IQR 1-2 vs median 2, IQR 1-2, P = 0.05).

Pediatric chest CT using photon-counting detector technology enables iodinated contrast dose reduction while preserving image quality compared with conventional EID CT at standard contrast doses.