Magnetic resonance in medicine : official journal of the Society of Magnetic Resonance in Medicine
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A dual-echo pulse sequence for simultaneous acquisition of MR angiography and venography (MRAV) is developed. Data acquisition of the second echo for susceptibility-weighted imaging-based MR venography is added to the conventional three-dimensional (3D) time-of-flight (TOF) MRA pulse sequence. Using this dual-echo acquisition approach, the venography data can be acquired without increasing the repetition time, and, therefore, the scan duration of routine TOF MRA scans is maintained. ⋯ The effect of spatial resolution on vein-to-background contrast is also demonstrated. Venous contrast is improved in high-resolution (0.52 x 0.52 x 1.6 mm(3)) images compared to that in standard-resolution (0.78 x 0.78 x 1.6 mm(3)) images. This MRAV technique enables the acquisition of MR venography without the need of an extra scan or injection of contrast agent in routine clinical brain exams at 3T.
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Most k-space-based parallel imaging reconstruction techniques, such as Generalized Autocalibrating Partially Parallel Acquisitions (GRAPPA), necessitate the acquisition of regularly sampled Cartesian k-space data to reconstruct a nonaliased image efficiently. However, non-Cartesian sampling schemes offer some inherent advantages to the user due to their better coverage of the center of k-space and faster acquisition times. On the other hand, these sampling schemes have the disadvantage that the points acquired generally do not lie on a grid and have complex k-space sampling patterns. ⋯ Because the undersampled non-Cartesian data cannot be reconstructed using a single GRAPPA kernel, several Cartesian patterns are selected for the reconstruction. This flexibility in terms of both the appearance and number of patterns allows this pseudo-Cartesian GRAPPA to be used with undersampled data sets acquired with any non-Cartesian trajectory. The successful implementation of the reconstruction algorithm using several different trajectories, including radial, rosette, spiral, one-dimensional non-Cartesian, and zig-zag trajectories, is demonstrated.