Enhancing the Detection of BOLD Signal in fMRI by Reducing the Partial Volume Effect

Figure 4

Simulation results of VSI represented as 𝑡-score maps of the “activations” using the template shown in Figure 3. (a) is the original 64 × 64 map (without VSI) obtained from the central portion (64 × 64) of the 𝑘-space of the synthetic data set shown in Figure 3, (b) is the 64 × 64 map shifted half-voxel along the horizontal direction, (c) is the 64 × 64 map shifted half-voxel along the vertical direction, and (d) is the 64 × 64 map shifted half-voxel along the diagonal direction. It is observed that the left column is blurred horizontally in (b), vertically in (c), and both horizontally and vertically in (d). The left column has the least blurring and typically has the highest 𝑡-scores in (a). The same column has the most severe burring and typically has the lowest 𝑡-scores in (d). The voxel-shifted interpolated 128 × 128 map (e) is the interspersed combination of (a), (b), (c), and (d). The location-dependent blurring and reduction of 𝑡-score seen in (a)–(d) was largely eliminated in (e). The SNR of the images is approximately 500 with Gaussian noise introduced to the complex 𝑘-space.