Poriol

30346053

Purpose
Magnetic resonance imaging protocols for the assessment of quantitative information suffer from long acquisition times since multiple measurements in a parametric dimension are required. To facilitate the clinical applicability, accelerating the acquisition is of high importance. To this end, we propose a model?based optimization framework in conjunction with undersampling 3D radial stack?of?stars data.

Theory and Methods
High resolution 3D T 1 maps are generated from subsampled data by employing model?based reconstruction combined with a regularization functional, coupling information from the spatial and parametric dimension, to exploit redundancies in the acquired parameter encodings and across parameter maps. To cope with the resulting non?linear, non?differentiable optimization problem, we propose a solution strategy based on the iteratively regularized Gauss?Newton method. The importance of 3D?spectral regularization is demonstrated by a comparison to 2D?spectral regularized results. The algorithm is validated for the variable flip angle (VFA) and inversion recovery Look?Locker (IRLL) method on numerical simulated data, MRI phantoms, and in vivo data.

Results
Evaluation of the proposed method using numerical simulations and phantom scans shows excellent quantitative agreement and image quality. T 1 maps from accelerated 3D in vivo measurements, e.g. 1.8 s/slice with the VFA method, are in high accordance with fully sampled reference reconstructions.

Conclusions
The proposed algorithm is able to recover T 1 maps with an isotropic resolution of 1 mm3 from highly undersampled radial data by exploiting structural similarities in the imaging volume and across parameter maps.

constrained reconstruction, inversion?recovery Look?Locker, imaging, model?based reconstruction, MRI, T1 quantification, variable flip angle

Rapid T1 quantification from high resolution 3D data with model?based reconstruction

Oliver Maier, Jasper Schoormans, Matthias Schloegl, Gustav J. Strijkers, Andreas Lesch, Thomas Benkert, Tobias Block, Bram F. Coolen, Kristian Bredies, Rudolf Stollberger

2019 Mar;

17724343

Subcellular compartmentalization has become an important theme in cell signaling such as spatial regulation of Ras by RasGRP1 and MEK/ERK by Sef. Here, we report spatial regulation of Raf kinase by RKTG (Raf kinase trapping to Golgi). RKTG is a seven-transmembrane protein localized at the Golgi apparatus. RKTG expression inhibits EGF-stimulated ERK and RSK phosphorylation, blocks NGF-mediated PC12 cell differentiation, and antagonizes Ras- and Raf-1-stimulated Elk-1 transactivation. Through interaction with Raf-1, RKTG changes the localization of Raf-1 from cytoplasm to the Golgi apparatus, blocks EGF-stimulated Raf-1 membrane translocation, and reduces the interaction of Raf-1 with Ras and MEK1. In RKTG-null mice, the basal ERK phosphorylation level is increased in the brain and liver. In RKTG-deleted mouse embryonic fibroblasts, EGF-induced ERK phosphorylation is enhanced. Collectively, our results reveal a paradigm of spatial regulation of Raf kinase by RKTG via sequestrating Raf-1 to the Golgi apparatus and thereby inhibiting the ERK signaling pathway.

EGF, ERK, Golgi, Raf-1, Ras, PAQR3

Spatial regulation of Raf kinase signaling by RKTG

Lin Feng, Xiaoduo Xie, Qiurong Ding, Xiaolin Luo, Jing He, Fengjuan Fan, Weizhong Liu, Zhenzhen Wang, and Yan Chen*

2007 Sep 4;