Sensitivity of physeal-metaphyseal tractography correlations with height velocity for fractional anisotropy threshold selection

Objective

Diffusion tensor imaging (DTI) tractography of the physeal-metaphyseal complex (PMC) provides insights into skeletal maturation. Fractional anisotropy (FA) minimal and maximal thresholds of 0.15 and 1.0, respectively, are commonly used to reconstruct tracts; these values were developed for highly organized tissues and may exclude the less organized hypertrophic and transitional zones that drive growth. Whether lowering the FA thresholds better captures growth-sensitive features and correlates with annualized height velocity is unknown. Material and methods: Forty-five healthy adolescents (20 boys; 12-17 years) underwent 3 T DTI of the distal femoral PMC. Deterministic tractography was performed using nine previously untested FA threshold combinations (FA_min: 0.05, 0.10, 0.15 paired with FA_max: 0.40, 0.50, 0.60) and a conventional threshold (0.15-1.0). Partial Pearson correlations between extracted metrics (tract FA, apparent diffusion coefficient [ADC], volume) and annualized height velocity were computed, controlling for Tanner stage.