Model-based reconstruction for simultaneous multi-slice T1 mapping using single-shot inversion-recovery radial FLASH

Abstract

Purpose: To develop a single-shot multi-slice $T_1$ mapping method by combing simultaneous multi-slice (SMS) excitations, single-shot inversion-recovery (IR) radial fast low-angle shot (FLASH), and a nonlinear model-based reconstruction method.

Methods: SMS excitations are combined with a single-shot IR radial FLASH sequence for data acquisition. A previously developed single-slice calibrationless model-based reconstruction is extended to SMS, formulating the estimation of parameter maps and coil sensitivities from all slices as a single nonlinear inverse problem. Joint-sparsity constraints are further applied to the parameter maps to improve $T_1$ precision. Validations of the proposed method are performed for a phantom and for the human brain and liver in 6 healthy adult subjects.

Results: Phantom results confirm good $T_1$ accuracy and precision of the simultaneously acquired multi-slice $T_1$ maps in comparison to single-slice references. In vivo human brain studies demonstrate the better performance of SMS acquisitions compared to the conventional spoke-interleaved multi-slice acquisition using model-based reconstruction. Aside from good accuracy and precision, the results of 6 healthy subjects in both brain and abdominal studies confirm good repeatability between scan and re-scans. The proposed method can simultaneously acquire $T_1$ maps for 5 slices of a human brain ( $0.75\times 0.75\times 5{\mathrm{mm}}^3$ ) or 3 slices of the abdomen ( $1.25\times 1.25\times 6{\mathrm{mm}}^3$ ) within 4 seconds.

Conclusions: The IR SMS radial FLASH acquisition together with a nonlinear model-based reconstruction enable rapid high-resolution multi-slice $T_1$ mapping with good accuracy, precision, and repeatability.

Keywords: ${\mathrm{T}}_1$ mapping; model-based reconstruction; radial FLASH; simultaneous multi-slice.