Iterative Soft-Thresholding Reconstruction for Time-Of-Flight MR Angiography

Kedar Khare¹, Luca Marinelli¹, Christopher J. Hardy¹, Kevin F. King²

The implementation of Compressed Sensing strategies for accelerated MRI applications typically involve iterative methods to minimize nonlinear functionals consisting of terms representing L1-norm, total variation, etc. Iterative approaches (e.g. conjugate gradient) involve computation of complex cost functions and the solution is also sensitive to the choice of free parameters associated with the various non-linear priors. In this paper we present an iterative soft-thresholding method with slowly decreasing thresholding parameter and apply it to reconstruction and analysis of Time-of-Flight MRA. This method is not sensitive to the choice of free parameters and the computations involve only Fourier and wavelet transforms, both of which can be implemented efficiently. This method may be used either for reducing the scan time or for improving the spatial resolution of TOF-MRA images for fixed scan time.