A method and apparatus for reconstruction of a region of interest (ROI)
for an object using an imaging system is provided. The imaging system may
substantially exactly reconstruct the ROI with a straight line
trajectory. In the straight line trajectory, the ROI is not bounded or
encircled by the actual trajectory of the source (e.g., no chords that
are composed from two points on the source trajectory intersect or fill
the ROI to be imaged). However, the ROI may be substantially
reconstructed by using "virtual" chords to reconstruct the ROI. The
virtual chords are such that no point on the trajectory is included in
the virtual chord (such as one that is parallel to the straight line
trajectory). These virtual chords may intersect and fill the ROI, thus
enabling substantially exact reconstruction. Further, in reconstructing
the image, the straight line trajectory may be assumed to be infinite in
length.