Single-shot Multi-slice T1 Mapping at High Spatial Resolution – Inversion- Recovery FLASH with Radial Undersampling and Iterative Reconstruction

ABSTRACT

Purpose:

To develop a method for T1 mapping at high spatial resolution and for multiple slices.

Methods:

The proposed method emerges as a single-shot inversion-recovery experiment which covers the entire spinlattice relaxation process by serial acquisitions of highly undersampled radial FLASH images, either in single-slice or multi-slice mode. Serial image reconstructions are performed in time-reversed order and first involve regularized nonlinear inversion (NLINV) to estimate optimum coil sensitivity profiles. Subsequently, the coil profiles are fixed for the calculation of differently T1-weighted frames and the resulting linear inverse problem is solved by a conjugate gradient (CG) technique. T1 values are obtained by pixelwise fitting with a Deichmann correction modified for multi-slice applications.

Results:

T1 accuracy was validated for a reference phantom. For human brain, T1 maps were obtained at 0.5 mm resolution for single-slice acquisitions and at 0.75 mm resolution for up to 5 simultaneous slices (5 mm thickness). Corresponding T1 maps of the liver were acquired at 1 mm and 1.5 mm resolution, respectively. All T1 values were in agreement with literature data.

Conclusion:

Inversion-recovery sequences with highly undersampled radial FLASH images and NLINV/CG reconstruction allow for fast, robust and accurate T1 mapping at high spatial resolution and for multiple slices.

Keywords:

Nonlinear inverse reconstruction, real-time MRI, spin-lattice relaxation, T1 contrast, T1 mapping.