Field‐Based Spatial Self‐Registration of Multicoil Hardware for <scp> B ₀ </scp> Field Control

PURPOSE: field control despite nonreproducible hardware placement between calibration and experimental sessions. METHODS: An algorithm was designed to estimate rigid transformations between 3D field maps acquired during hardware calibration (Reference field) and subsequent experiments (Measured field). Hardware misplacement was determined by co-registration of the two fields within a defined region of interest. Simulations using Biot-Savart-derived MC basis fields and experimental validation with a 48-channel MC array at 3 T were used to quantify localization accuracy under varying signal-to-noise ratio (SNR) levels. A genetic algorithm optimized coil currents to generate a Reference field shape that yielded minimal self-registration error. RESULTS: Simulations and measurements demonstrated that submillimeter (≤ 0.5 mm) and subdegree (≤ 0.5°) localization accuracy is achievable at practical SNR levels (≥ 5). Errors decreased with increasing SNR and field complexity. The optimized field produced by the genetic algorithm yielded the lowest mean translation error (0.20 mm) and rotation error (0.11°), consistent with theoretical predictions. Self-registration computation required less than 10 s per case. CONCLUSION: shimming performance in insert-based or repositionable MR systems.