Simultaneous multi-band multi-spectral imaging using multi-band RF excitation for accelerated metal artifact...

Magnetic resonance imaging (MRI) provides high soft tissue contrast and accurate spatial guidance for interventional procedures. However, metallic needles introduce severe signal voids and phase accumulation that can obscure surrounding anatomy and target lesions, thus compromising procedural accuracy and increasing the risk of injury to adjacent healthy tissue.

To reduce metal-induced artifacts and shorten acquisition time in MRI-guided interventions while improving imaging precision during needle guidance.

We propose a simultaneous multi-band multi-spectral imaging (SMB-MSI) sequence that uses multi-band radiofrequency pulses, designed from off-resonance field maps estimated using low-resolution two-dimensional multi-spectral imaging (2D MSI) data to acquire multiple spectral bins concurrently. In the current implementation, the proposed SMB-MSI data were acquired from two simultaneously excited bins and reconstructed using direct complex summation.The performance of SMB-MSI was evaluated against fast low-angle shot (FLASH), two-dimensional fast spin echo (2D FSE), and conventional MSI with different numbers of spectral bins using phantom experiments and ex vivo porcine liver models. Puncture needles were imaged at 0.35 T and 1.5 T. Metal-induced artifact width was quantified using the full width at half maximum (FWHM), and image signal-to-noise ratios (SNRs) were assessed in both phantom and ex vivo porcine liver experiments.

SMB-MSI markedly reduced artifact width (e.g., 3.8 vs. 5.8 mm and 4.2 vs. 6.6 mm in phantom experiments, and 2.3 vs. 3.7 mm, 2.8 vs. 4.2 mm at 0.35 T and 1.5 T, respectively, relative to five-bin MSI), while shortening acquisition time by approximately 80% compared with five-bin MSI. In addition, SMB-MSI provided higher SNR than conventional MSI in both phantom and ex vivo experiments. Needle tips were clearly visualized with minimal geometric distortion. Consistent improvements were observed in both phantom and ex vivo liver experiments at both field strengths.

SMB-MSI provides rapid and accurate MRI-guided needle visualization with substantially reduced metal-induced artifacts. This approach shows promise for improving the efficiency and precision of MRI-guided interventional procedures.