Repeatability of diffusion-based stiffness prediction - A healthy volunteer study.

INTRODUCTION

The study investigated the repeatability of brain diffusion-based stiffness prediction (DWI) in healthy volunteers.

METHODS

Thirty-one healthy volunteers were examined with DWI using two different sets of b-values: b200-1500 s/mm (DWI, 1500) and b200-1000 s/mm (DWI, 1000). Each b-value set was scanned twice per imaging session without repositioning the participants. DWI images were reconstructed from each set. Two observers delineated regions of interest (ROIs) on each DWI image. The repeatability coefficient (RC), coefficient of variation (CV), inter- and intraobserver agreement were calculated.

RESULTS

After excluding three participants due to image artifacts, the study included twenty-eight volunteers (mean age (range)) 37 years (24-62), 10 males, 18 females). For DWI, 1500, the lowest and the highest RCs were in the parietal lobe (0.52) and respectively the brain stem (1.17). The lowest RC for DWI, 1000 was in the frontal lobe (0.42) and the highest in the brain stem (1.58). The CV for whole brain measurements was 3.83 % for DWI, 1500 and 4.93 % for DWI, 1000. The Bland‒Altman (BA) limits of agreement (LoA) for the intraobserver agreement of DWI, 1500 were -0.90 to 1.06 and respectively -0.78 to 0.88 for DWI, 1000. Regarding interobserver agreement, the LoA were -0.85 to 0.94 for DWI, 1500 and -0.61 to 0.66 for DWI, 1000.

CONCLUSION

DWI is a precise technique with some observer dependence. Repeatability is higher for DWI, 1000 s/mm than for DWI 1500 s/mm.

IMPLICATIONS FOR PRACTICE

Our findings suggest that DWI can reliably detect stiffness changes larger than 4.93 % in healthy volunteers. Further studies should investigate whether the repeatability of DWI may be affected by the presence of pathology such as a brain tumor.