Evaluating the correlation between pediatric exposure rates and common body size surrogates in fluoroscopy

To quantify the degree of correlation between pediatric radiation exposure rates and commonly used body size surrogates: anteroposterior (AP) or lateral (LAT) body thickness, weight, height, body mass index (BMI), body surface area (BSA), and age, for general fluoroscopy (GF) and cardiac fluoroscopically guided interventional (cardiac FGI) examinations, as a way to identify the most predictive surrogate to optimize dose management and exposure control across a wide range of pediatric body sizes.

This retrospective study included 6447 GF examinations, from 4452 pediatric patients, and 2968 cardiac FGI examinations, from 1471 patients, aged from birth to 21 years. Reference air kerma (RAK) data, collected from a radiation dose index monitoring database, were corrected using calibration measurements with accuracy better than ± 5%. Exposure rate was calculated as RAK divided by total fluoroscopy time. Patient body size surrogates: measured AP or LAT thickness, age, weight, height, BMI, and BSA were extracted or computed from recorded data. Correlations between log-transformed exposure rates and body size surrogates were evaluated using Pearson's correlation coefficients. Steiger's Z-test was applied to assess statistically significant differences between dependent correlations.

For GF examinations, AP thickness correlated most strongly with exposure rate (r = 0.691), followed by BSA (r = 0.574) and weight (r = 0.568). BMI showed the weakest correlation (r = 0.446). For cardiac FGI examinations, weight demonstrated the highest correlation with exposure rate in both frontal (r = 0.689) and LAT (r = 0.794) planes, with BSA and LAT thickness performing similarly. All other correlations were significantly lower (p < 0.001). The superior performance of AP thickness in GF reflects its direct relationship to X-ray attenuation, whereas variable geometry and positioning during cardiac FGI favor weight as a more stable predictor.

For pediatric fluoroscopy, AP thickness best predicts exposure rate in GF, while weight is the most reliable surrogate for cardiac FGI procedures. Selecting modality-specific size metrics enhances pediatric dose optimization and supports consistent radiation exposure management across all patient sizes.