Consistency of fractional anisotropy values using different combinations of B-value and time of echo (TE) in diffusion tensor imaging of normal brain white matter

Introduction: Fractional Anisotropy (FA) values are considered as a solid concrete index for determining white matter integrity in ageing and neurodegenerative diseases. FA is more comparable and reliable parameter than individual diffusivity parameters. A b-value and Time of Echo (TE) significantly affect the reproducibility and accuracy of Diffusion Tensor Imaging (DTI) derived indices at 1.5 Tesla (T) MRI machines in grey and white matter. Hence, no fixed b-value and TE protocol combination is recommended in literature to obtain consistent FA values, as it is a relatively new imaging technique. Aim: To check the consistency of FA values using different combinations of b-value and TE in DTI of normal brain white matter and to establish a standardised protocol for calculating FA values in different regions of normal brain white matter of the corpus callosum, centrum semiovale and pons. Materials and Methods: A cross-sectional study of 23 healthy participants without neurological abnormalities using 1.5 T MRI, DTI of brain white matter was performed. FA values were measured at the corpus callosum, centrum semiovale and pons using fiber track analysis in six different combinations of b-value and TE. Results: The FA values with least coefficient of variation was found with a b-value of 1000 s/mm² and TE 100 ms. Conclusion: The current study established a standardised protocol for calculating FA values in different regions of normal brain white matter of the corpus callosum, centrum semiovale and pons.