Generalizing Diffusion Tensor Imaging of the Physis and Metaphysis

Abstract

BackgroundCurrent methods to predict height potential are inaccurate. Predicting height by using MRI of the physeal cartilage has shown promise but the applicability of this technique in different imaging setups has not been well‐evaluated.PurposeTo assess variability in diffusion tensor imaging of the physis and metaphysis (DTI‐P/M) of the distal femur between different scanners, imaging parameters, tractography software, and resolution.Study TypeProspective.Population/SubjectsEleven healthy subjects (five males and six females ages 10–16.94).Field Strength/Sequence3 T; DTI single shot echo planar sequences.AssessmentPhyseal DTI tract measurements of the distal femur were compared between different scanners, imaging parameters, tractography settings, interpolation correction, and tractography software.Statistical TestsBland–Altman, Spearman correlation, linear regression, and Shapiro–Wilk tests. Threshold for statistical significance was set at P = 0.05.ResultsDTI tract values consistently showed low variability with different imaging and analysis settings. Vendor to vendor comparison exhibited strong correlation (ρ = 0.93) and small but significant bias (bias −5.76, limits of agreement [LOA] −24.31 to 12.78). Strong correlation and no significant difference were seen between technical replicates of the General Electric MRI scanner (ρ = 1, bias 0.17 [LOA −1.5 to 1.2], P = 0.42) and the Siemens MRI scanner (ρ = 0.89, bias = 0.56, P = 0.71). Different voxel sizes (1 × 1 × 2 mm3 vs. 2 × 2 × 3 mm3) did not significantly affect DTI values (bias = 1.4 [LOA −5.7 to 8.4], P = 0.35) but maintained a strong correlation (ρ = 0.82). Gap size (0 mm vs. 0.6 mm) significantly affects tract volume (bias = 1.8 [LOA −5.4 to 1.8]) but maintains a strong correlation (ρ = 0.93). Comparison of tractography algorithms generated significant differences in tract number, length, and volume while maintaining correlation (ρ = 0.86, 0.99, 0.93, respectively). Comparison of interobserver variability between different tractography software also revealed significant differences while maintaining high correlation (ρ = 0.85–0.98).Data ConclusionDTI of the pediatric physis cartilage shows high reproducibility between different imaging and analytic parameters.Evidence Level2Technical EfficacyStage 1