Inversion recovery with embedded self-calibration (IRES)

With self-calibrated parallel acquisition, the calibration data used to characterize coil response are acquired within the actual, parallel scan. Although this eliminates the need for a separate calibration scan, it reduces the net acceleration factor of the parallel scan. Furthermore, this reduction gets worse at higher accelerations. A method is described for three-dimensional inversion recovery gradient-echo imaging in which calibration is incorporated into the sequence but with no loss of net acceleration. This is done by acquiring the calibration data using very small (≤4°) tip angle acquisitions during the delay interval after acquisition of the accelerated imaging data. The technique is studied at 3 Tesla with simulation, phantom, and in vivo experiments using both image-space-based and k-space-based parallel reconstruction methods. At nominal acceleration factors of 3 and 4, the newly described inversion recovery with embedded self-calibration (IRES) method can retain effective acceleration with comparable SNR and contrast to standard self-calibration. At a net two-dimensional acceleration factor of 4, IRES can achieve higher SNR than standard self-calibration having a nominal acceleration factor of 6 but the same acquisition time.