Figure 1.

M-line reconstruction for the partial-circle-plus-arc trajectory. For each location ${\underset{̱}{x}}_0$ inside the ROI, there is one associated M-line and one associated π-line. The M-line defines the filtering directions for ${\underset{̱}{x}}_0$. The π-line delimitates the portion of the trajectory (shown in dark) from where the data must be backprojected onto ${\underset{̱}{x}}_0$ to perform a theoretically exact reconstruction at ${\underset{̱}{x}}_0$.