Femoral Skeletal Growth in Early Infancy Assessed by Radiofrequency Echographic Multi‐Spectrometry

BACKGROUND: Early skeletal growth represents a critical window for lifelong bone health and is influenced by genetic, nutritional, and environmental factors. However, the assessment of bone status during infancy remains challenging due to the limited feasibility of reference densitometric techniques for longitudinal use. Radiofrequency echographic multi-spectrometry (REMS) is an ultrasound-based technology validated for bone mineral density (BMD) assessment in adults, but its applicability to early infancy has not yet been established. This study aimed to explore a REMS-based approach for investigating femoral skeletal growth during early life. METHODS: Eighty-two healthy term infants underwent femoral REMS examinations at 3 and 6 months of age. Unfiltered radiofrequency ultrasound signals were analyzed using a multivariate framework combining fast Fourier transform (FFT) spectral analysis with partial least squares (PLS) regression. Body weight was used as an indirect surrogate marker of skeletal growth, with spectral features serving as predictors. RESULTS: Average power spectra stratified according to PLS-inferred body weight demonstrated distinct spectral patterns between lower- and higher-weight infants. The PLS-based spectral model showed longitudinal consistency, preserving relative skeletal status across time points. These findings indicate that REMS-derived spectral features vary systematically with growth-related physiological changes during infancy. CONCLUSIONS: REMS-derived spectral characteristics appear to be sensitive to early skeletal growth processes in infancy. Although further studies incorporating direct bone outcomes are required to disentangle the relative contributions of body size and mineralization, this work provides foundational evidence supporting the feasibility of extending REMS technology to early life. REMS may represent a promising non-invasive and radiation-free approach for longitudinal investigation of skeletal development in pediatric populations.