Acceleration apportionment: A method of improved 2D SENSE acceleration applied to 3D contrast-enhanced MR angiography

Purpose In 2D SENSE-accelerated 3D Cartesian acquisition, the net acceleration factor R is the product of the two individual accelerations, R = R_Y × R_Z. Acceleration Apportionment tailors acceleration parameters (R_Y, R_Z) to improve parallel imaging performance on a patient- and coil-specific basis and is demonstrated in contrast-enhanced MR angiography. Methods A performance metric is defined based on coil sensitivity information which identifies the (R_Y, R _Z) pair that optimally trades off image quality with scan time reduction on a patient-specific basis. Acceleration Apportionment is evaluated using retrospective analysis of contrast-enhanced MR angiography studies, and prospective studies in which optimally apportioned parameters are compared with standard acceleration parameters. Results The retrospective studies show strong variability in optimal acceleration parameters between anatomic regions and between patients. Prospective application of apportionment to foot contrast-enhanced MR angiography with an 8-channel receiver array provides a 20% increase in net acceleration with improved contrast-to-noise ratio. Application to 16-channel contrast-enhanced MR angiography of the feet and calves suggests 10% acceleration increase to R > 13 and no contrast-to-noise ratio loss. The specific implementation allows the optimum (R_Y, R_Z) pair to be determined within one minute. Conclusion Optimum 2D SENSE acceleration parameters can be automatically chosen on a per-exam basis to allow improved performance without disrupting the clinical workflow.