Whole-brain T2 mapping with radial sampling and retrospective motion correction at 3T.

Purpose: Several barriers prevent the use of whole-brain T₂ mapping in routine use despite increasing interest in this parameter. One of the main barriers is the long scan time resulting in patient discomfort and motion corrupted data. To address this challenge, a method for accurate whole-brain T₂ mapping with a limited acquisition time and motion correction capabilities is investigated.

Methods: A 3D radial multi-echo spin-echo sequence was implemented with optimized sampling trajectory enabling the estimation of intra-scan motion, subsequently used to correct the raw data. Motion corrected echo images are then reconstructed with linear subspace constrained reconstruction. Experiments were carried out on phantom and volunteers at 3T to evaluate the accuracy of the T₂ estimation, the sensitivity to lesions and the efficiency of the correction on motion corrupted data.

Results: Whole-brain T₂ mapping acquired in less than 7 min enabled the depiction of lesions in the white matter with longer T₂. Data retrospectively corrupted with typical motion traces of pediatric patients highly benefited from the motion correction by reducing the error in T₂ estimates within the lesions. All datasets acquired on seven volunteers, with deliberate motion, also showed that motion corrupted T₂ maps could be improved with the retrospective motion correction both at the voxel level and the structure level.

Conclusion: A whole-brain T₂ mapping sequence with retrospective intra-scan motion correction and reasonable acquisition time is proposed. The method necessitates advanced iterative reconstruction strategies but no additional navigator, external device, or increased scan time is required.