An Adjustable Photon Detection System (APDS) for multi-slice X-ray CT systems and a multi-slice X-ray CT system using the APDS are disclosed wherein the APDS can be adjusted to be aligned to different X-ray source positions wherein the multi-slice X-ray CT system comprises one or more X-ray sources, and one or more APDS wherein the multi-slice X-ray CT system may also include a detector position calculator for calculating effective detector positions and a detector position corrector for correcting projection data using calculated effective detector positions.
