Research Article
Quick Reduction of Specific Absorption Rate Constraints in Parallel RF Excitation Pulse Design by Maximum Volume Inscribed Ellipsoids
Table 3
Optimization of AFA and STA objective functions for the excitation and inversion examples without and with proposed MVIE SAR reduction.
| MVIE SAR reduction | no | yes |
| Number of SAR constraints | 491 | 1 | Average power constraints | 8 | 8 |
| 30-degree excitation with 5 points |
| Number of RF constraints | 40 | 40 |
| Arbitrary flip angle optimization (AFA) |
| Computation time [s] | 2.63 | 1.24 | Iteration count | 41 | 38 | Root mean square error [deg] | 1.63 | 1.87 |
| Small tip angle approximation (STA) |
| Computation time [s] | 1.87 | 0.89 | Iteration count | 38 | 41 | Root mean square error [deg] | 1.64 | 1.90 |
| 180-degree inversion with 7 points |
| Number of RF constraints | 56 | 56 |
| Arbitrary flip angle optimization (AFA) |
| Computation time [s] | 8.52 | 2.87 | Iteration count | 84 | 55 | Root mean square error [deg] | 15.44 | 15.44 |
| Small tip angle approximation (STA) |
| Computation time [s] | 4.84 | 1.44 | Iteration count | 65 | 52 | Root mean square error [deg] | 10.38 | 10.38 |
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