A combined back-projection and Fourier transform MRI method

摘要

Measuring data is taken according to a projection method by means of gradient rotation. Instead of being passed to a conventional back-projection algorithm, the data is used to prepare a rectangular array in k-space suitable for 2D or 3D Fourier transformation. A rectangular matrix is imposed on k-space and a new value is assigned to the centre of each cell by assignment of a measured point or by averaging or weighted averaging of measured points within the cell. Alternatively, a function may be fitted to the measured points and values computed from this function. The strength of the gradient may be adjusted between projections so that measured points lie on concentric squares. A rapid projection method using FIDs instead of echoes is disclosed, in which the initial FID portion is rendered observable by reducing the gradient to slow down the FID evolution. IMAGE