Craniofacial Imaging of Pediatric Patients by Ultrashort Echo-Time Bone- Selective MRI in Comparison to CT

Rationale and objectives: The emergence of low-dose protocols for CT imaging has mitigated pediatric radiation exposure, yet ionizing radiation remains a concern for children with complex craniofacial conditions requiring repeated radiologic monitoring. In this work, the clinical feasibility of an ultrashort echo time (UTE) MRI sequence was investigated in pediatric patients. Materials and Methods: Twelve pediatric patients (6 female, age range 8 to 18 years) with various imaging conditions were scanned at 3T using a dual-radiofrequency, dual-echo UTE MRI sequence. Bright-bone images were generated using a weighted least-squares conjugate gradient method to enhance bone specificity. The overlap of the binary skull masks was quantified using the Dice similarity coefficient (DSC) and the 95th percentile Hausdorff distance (HD95) to evaluate the similarity between MRI and CT. To assess the anatomic accuracy of 3D skull reconstructions, six craniometric distances were recorded and the agreement between MRI- and CT- derived measurements was evaluated using Lin's concordance correlation coefficient (rho c). Results: The bright-bone images from UTE MRI demonstrated high bone-contrast, suppression of soft tissue, and separation from air at the sinuses. The DSC and HD95 between MRI and CT had medians of 0.81 +/- 0.10 and 1.87 +/- 0.32 mm, respectively. There was good agreement between MRI and CT for all craniometric distances (rho c ranging from 0.90 to 0.99) with a mean absolute difference in measurements of < 2 mm. Conclusion: The clinical feasibility of the UTE MRI sequence for craniofacial imaging was demonstrated in a cohort of pediatric patients, showing good agreement with CT in resolving thin bone structures and craniometry.