Accurate brain volumetry with diffusion-weighted spin-echo single-shot echo-planar-imaging and dual-clustering segmentation: comparison with volumetry-validated quantitative magnetic resonance imaging.

PURPOSE: Although the diffusion-weighted spin-echo single-shot echo-planar-imaging (DW-SE-sshEPI) is an established quantitative MRI (qMRI) pulse sequence, it is known to be vulnerable to geometric distortions. The purpose of this work is to study is to study brain volumetry accuracy with DW-SE-sshEPI relative previously published volumetry-validated qMRI pulse sequence, specifically the mixed turbo spin-echo (mixed-TSE) pulse sequence, which is robust to magnetic field inhomogeneities and affords much higher spatial resolution.
METHODS: Twenty-eight subjects were imaged with both DW-SE-sshEPI and mixed-TSE pulse sequences. For each subject, the intracranial structures were segmented using a single-qMRI-channel dual-clustering algorithm (for DW-SE-sshEPI) and a three-qMRI-channel dual-clustering algorithm (for mixed-TSE). The respective intracranial volumes were calculated with both data sets and then compared.
RESULTS: The intracranial volumes derived from DW-SE-sshEPI and mixed-TSE data sets are highly and linearly correlated (R2 = 0.9353) with a slope of 0.9911, with one distorted DW-SE-sshEPI data set demonstrating remarkable volume underestimation. Excluding this outlier resulted in improved linear correlation (R2 = 0.9681) with a slope of 1.0003.
CONCLUSIONS: Brain volumetry with DW-SE-sshEPI at 1.5 T data sets can be very accurate for most patients for whom the major magnetic field inhomogeneities result from typical tissue interfaces (e.g., air-tissue or bone-tissue) and typical dental fillings, but not from larger metallic implants.