Template method to improve brain segmentation from inhomogeneous brain magnetic resonance images at high fields

Magnetic resonance imaging of the brain at high fields (e.g. 3T) provides high resolution and high signal to noise ratio images suitable for a wide range of clinical applications. However, radiofrequency (or B₁) inhomogeneity increases with the magnetic field and produces undesired intensity variations responsible for inaccuracies in quantitative analyses. A method to perform brain segmentation using T₁ maps whose inhomogeneity was corrected using previously acquired B₁ maps is described. A library of B₁ maps was created and a method to compensate the T₁ inhomogeneity using a B₁ map from another subject (template) was developed. The performance of the template-based method was evaluated in 19 healthy volunteers. Our method produced significantly better segmentations than the retrospective N3 method and the one without B₁ inhomogeneity correction.