Sub-mSv CT for pediatric and young adult hip imaging: a low-radiation-dose alternative to pelvic radiography.

backgroundRadiography is routinely used to evaluate the pediatric and young adult pelvis and hips. Unfortunately, the 2D nature of this imaging modality is insufficient in accurately depicting and evaluating complex 3D anatomical structures. In contrast, computed tomography (CT) provides exquisite details of 3D anatomy, typically at the expense of a higher radiation dose. Recent studies have suggested that ultra-low-dose CT (ULDCT) with tin filtration may overcome this diagnostic imaging dilemma by offering high-quality CT images with reduced radiation exposure.

objectiveTo compare patient-specific radiation exposure of diagnostic-quality hip ULDCTs and pelvic radiographs and thereby validate an optimized clinical protocol for hip ULDCT imaging in pediatric and young adult patients. MATERIALS AND

methodsWe retrospectively searched the image archive at our large tertiary children's hospital for hip CTs and anteroposterior (AP) pelvic radiographs performed within 6 months of each other (Dec 2023 - May 2024). The inclusion criteria were (1) hip CTs performed in accordance with our established ULDCT imaging protocol and (2) AP pelvic radiographs acquired in accordance with the American College of Radiology (ACR) guidelines. To calculate the effective doses of the pelvic radiographs and hip CTs, we used the National Cancer Institute dosimetry system for Radiography and Fluoroscopy (NCIRF) and Computed Tomography (NCICT), respectively. A paired two-tailed t-test was used to compare the effective doses of the hip CTs and AP pelvic radiographs.

resultsThe study cohort included 29 patients (9 males, 20 females), stratified into the pediatric group (<18 years, n=17), young adult group (18-30 years, n=12), and entire cohort, with mean ages of 10.7 (SD, 6.0), 22.3 (SD, 3.7), and 15.5 (SD, 6.9) years, respectively. The average effective doses from ULDCT were 0.33 mSv (pediatric), 0.23 mSv (young adult), and 0.29 mSv (entire cohort), not significantly different from AP pelvic radiograph doses of 0.26, 0.29, and 0.27 mSv, respectively. In contrast, cumulative radiographic doses were significantly higher at 0.73 mSv, 0.76 mSv, and 0.74 mSv.

conclusionULDCT is a clinically feasible approach for pediatric and young adult hip imaging, offering diagnostic-quality CT images with substantially reduced radiation exposure (at a radiation dose level comparable to that of a single AP pelvic radiograph).