Photon-counting Detector CT Enables Pediatric Low-dose Chest Imaging With Further Reduction of Radiation Exposure

Background: Photon-counting detector computed tomography (PCD CT) offers higher dose efficiency than conventional energy-integrating detector CT (EID CT), which is particularly beneficial for children. Broad evidence is missing whether frequently acquired pediatric low-dose lung imaging can be further improved using PCD CT. Objective: To compare radiation exposure, quantitative and qualitative image quality of pediatric low-dose chest PCD CT versus EID CT examinations. Methods: Unenhanced low-dose chest PCD CT and EID CT examinations acquired for clinical indications were retrospectively compared. Cohorts were matched by water-equivalent diameter (D w ) and age (n=44 each; median age 6.3 y PCD CT vs. 7.4 y EID CT). Radiation exposure was analyzed by volume CT dose index (CTDI vol ), dose length product (DLP), and size-specific dose estimate (SSDE). Quantitative image quality assessment featured the placement of regions of interest (ROIs) in the lung, heart, and liver for the extraction of mean attenuation, noise, signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and figures of merit (FOMs). Qualitative image quality was evaluated by 3 readers using Likert scales and additional direct comparisons in a blinded manner. Results: Weight, height, and body mass index (BMI) were not significantly different between the 2 cohorts ( P >0.05). PCD CT examinations showed lower median CTDI vol (0.27 vs. 0.39 mGy, P <0.0001), DLP (6.71 vs. 8.75 mGy*cm, P <0.0001), and SSDE (0.55 vs. 0.83 mGy, P <0.0001) compared with EID CT. Mean attenuation [−797.76 vs. −772.50 Hounsfield units (HU), P =0.51], noise (17.82 vs. 17.69 HU, P =0.73), SNR (−46.10 vs. −45.40, P =0.63), and CNR (39.26 vs. 39.76, P =0.68) of lung parenchyma were not significantly different; respective dose efficiency expressed by FOM was higher in PCD CT compared with EID CT (mean 8030 vs. 5482 mGy −1 , P <0.0001). Qualitative rating showed equal and overall excellent scores for both cohorts. Conclusions: PCD CT enables pediatric low-dose chest imaging with lower radiation exposure at similar image quality compared with EID CT.