Retrospective Co-RASOR Reconstruction and Post-Processing Enable Efficient and Accurate Localization of Objects and Devices

Hendrik de Leeuw¹, Peter R. Seevinck¹, Chris J.G. Bakker¹

Accurate localization of field perturbing objects e.g. needles, catheters and brachytherapy seeds, is difficult with MRI since induced signal voids are non-specific and distorted. Center-out Radial Sampling with Off-Resonance reception (co-RASOR) has been shown to locate perturbers accurately with high positive contrast, by selecting the optimum from many off-resonance acquisitions. Herein the efficiency and flexibility is significantly increased by making multiple off-resonance reconstructions from one on-resonance acquisition and automatically extracting the optimal frequency offset. The equivalence in accuracy of co-RASOR and CT is demonstrated by a phantom experiment, its flexibility with an arbitrarily oriented biopsy needle in inhomogeneous porcine tissue.