Simultaneous outer volume and blood suppression by quadruple inversion-recovery

A new method has been developed for reduced field-of-view (FOV) imaging with simultaneous blood suppression. This method combines suppression of signals from the outer volume and inflowing blood by using a small-FOV quadruple inversion-recovery (SFQIR) preparative pulse sequence consisting of two double-inversion pulse pairs separated by appropriate delays. Within each pair, inversion pulses are successively applied to the imaged slice and the slab orthogonal to the imaging plane with the thickness equal to the FOV size in the phase-encoding direction. Each double inversion results in the reinversion of the magnetization in the central part of the FOV, while the outer areas of the FOV and inflowing blood remain inverted. The SFQIR module was implemented for single- and multislice acquisition with a fast spin-echo readout sequence. Based on a theoretical model of the signal, the timing parameters of the sequence corresponding to the maximal suppression efficiency can be found by minimizing the variation of the normalized signal over the entire range of T-1's that occur in tissues. The method was tested for black-blood imaging of the aorta and carotid arteries, and the results demonstrated its ability to eliminate motion and flow artifacts, reduce scan time, and improve spatial resolution.