  In scintillation detector, scintillation crystals are typically made into
2-dimension modular array. The location of incident gamma-ray need be
calibrated due to spatial response nonlinearity. Generally, position
histograms, the characteristic flood response of scintillation detectors, are
used for position calibration. In this paper, a position calibration method
based on crystal position lookup table which maps the inaccurate location
calculated by Anger logic to the exact hitting crystal position has been
proposed, Firstly, position histogram is segmented into disconnected regions.
Then crystal marking points are labeled by finding the centroids of regions.
Finally, crystal boundaries are determined and crystal position lookup table is
generated. The scheme is evaluated by the whole-body PET scanner and breast
dedicated SPECT detector developed by Institute of High Energy Physics, Chinese
Academy of Sciences. The results demonstrate that the algorithm is accurate,
efficient, robust and general purpose.
