Generalizing Diffusion Tensor Imaging of the Physis and Metaphysis

Background

Current 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.

Purpose

To 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 Type

Prospective.

Population/Subjects

Eleven healthy subjects (five males and six females ages 10–16.94).

Field Strength/Sequence

3 T; DTI single shot echo planar sequences.

Assessment

Physeal DTI tract measurements of the distal femur were compared between different scanners, imaging parameters, tractography settings, interpolation correction, and tractography software.

Statistical Tests

Bland–Altman, Spearman correlation, linear regression, and Shapiro–Wilk tests. Threshold for statistical significance was set at P = 0.05.

Results

DTI 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 Conclusion

DTI of the pediatric physis cartilage shows high reproducibility between different imaging and analytic parameters.

Evidence Level

2

Technical Efficacy

Stage 1