Simultaneous Acquisition of Diffusion Tensor and Dynamic Diffusion MRI

Abstract

Background: Dynamic diffusion magnetic resonance imaging (ddMRI) metrics can assess transient microstructural alterations in tissue diffusivity but requires additional scan time hindering its clinical application.

Purpose: To determine whether a diffusion gradient table can simultaneously acquire data to estimate dynamic and diffusion tensor imaging (DTI) metrics.

Study type: Prospective.

Subjects: Seven healthy subjects, 39 epilepsy patients (15 female, 31 male, age ± 15).

Field strength/sequence: Two-dimensional diffusion MRI (b = 1000 s/mm² ) at a field strength of 3 T. Sessions in healthy subjects-standard ddMRI (30 directions), standard DTI (15 and 30 directions), and nested cubes scans (15 and 30 directions). Sessions in epilepsy patients-two 30 direction (standard ddMRI, 10 nested cubes) or two 15 direction scans (standard DTI, 5 nested cubes).

Assessment: Fifteen direction DTI was repeated twice for within-session test-retest measurements in healthy subjects. Bland-Altman analysis computed bias and limits of agreement for DTI metrics using test-retest scans and standard 15 direction vs. 5 nested cubes scans. Intraclass correlation (ICC) analysis compared tensor metrics between 15 direction DTI scans (standard vs. 5 nested cubes) and the coefficients of variation (CoV) of trace and apparent diffusion coefficient (ADC) between 30 direction ddMRI scans (standard vs. 10 nested cubes).

Statistical tests: Bland-Altman and ICC analysis using a P-value of 0.05 for statistical significance.

Results: Correlations of mean diffusivity (MD), axial diffusivity (AD), and radial diffusivity (RD) were strong and significant in gray (ICC > 0.95) and white matter (ICC > 0.95) between standard vs. nested cubes DTI acquisitions. Correlation of white matter fractional anisotropy was also strong (ICC > 0.95) and significant. ICCs of the CoV of dynamic ADC measured using repeated cubes and nested cubes acquisitions were modest (ICC >0.60), but significant in gray matter.

Conclusion: A nested cubes diffusion gradient table produces tensor-based and dynamic diffusion measurements in a single acquisition.

Level of evidence: 2 TECHNICAL EFFICACY: Stage 1.

Keywords: acquisition; brain; diffusion tensor imaging; dynamic diffusion; gradient orientation; neuroimaging.