Abstract
To develop a single-shot multi-slice 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. 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 precision. Validations of the proposed method are performed for a phantom and for the human brain and liver in 6 healthy adult subjects. Phantom results confirm good accuracy and precision of the simultaneously acquired multi-slice 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 maps for 5 slices of a human brain ( ) or 3 slices of the abdomen ( ) within 4 seconds. The IR SMS radial FLASH acquisition together with a nonlinear model-based reconstruction enable rapid high-resolution multi-slice mapping with good accuracy, precision, and repeatability.
Highlights
Quantitative mapping of MR relaxation times such as T1 finds increasing applications in a variety of clinical use cases [1, 2]
Mapping of T1 relaxation time commonly relies on the inversion-recovery (IR) Look-Locker sequence where RF excitations are continuously applied after inversion followed by computation of a T1 map in a postprocessing step [3,4,5]
The proposed method was first validated in a phantom study using the simultaneous multi-slice (SMS) golden-angle acquisition and the developed SMS model-based reconstruction
Summary
Quantitative mapping of MR relaxation times such as T1 finds increasing applications in a variety of clinical use cases [1, 2]. Advances in sequence development such as non-Cartesian sampling together with state-of-the-art reconstruction techniques have enabled faster parameter mapping [6,7,8,9,10,11,12,13], including accelerated T1 mapping within a single inversion recovery [14,15,16]. These methods usually consist of two steps: First, reconstruction of contrast-weighted images from undersampled datasets and, second, subsequent voxel-by-voxel fitting of the T1 map. A priori information such as sparsity constraints can be applied to the parameter maps to improve precision [6, 20, 22, 25]
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