VSSI-TBM: A variational sparse source imaging method based on time basis matrix

Source imaging algorithms have been widely used to localize functional and lesion areas. Brain source reconstruction is limited by complex experimental environments (noise interference, distributed brain activity, acquisition systems, etc.), and range estimation is not accurate. This study proposes a variational sparse source imaging method based on the time basis matrix (VSSI-TBM) algorithm. VSSI-TBM permits the source spatial signal to consist of several temporal basis functions by using low-rank decomposition to extract effective signals. In a compressed space, mixed-norm constraints and a cortical source variation operator ensure spatial sparsity and smoothness. In clinical examinations or research, other a priori information regarding brain activity may be available. VSSI-TBM using lead field guide constraints can further enhance the reconstruction results. The simulation results demonstrate the robust performance of VSSI-TBM in environments with a low signal-to-noise ratio (SNR), large sources (>11cm²), and multiple sources. Additionally, integrating prior information enhances the imaging performance in complex environments. The algorithm is evaluated using an open-source dataset and an optically pumped magnetometer-based magnetoencephalography (OPM-MEG) system with a noisy 30-channel uniform layout. The results reveal a strong robustness of the spatial range reconstruction. Moreover, the combination of prior information effectively improves the imaging performance of the OPM-MEG system.