For calibration (24) for quantitative SPECT, a multiple energy emission source (11) is used for calibration. The planar sensitivities and/or uniformities are determined at different emission energies based on detections from the multiple energy emission source. For estimating (32) the activity concentration, sensitivities and/or uniformities based on measures (26) at different emission energies increase accuracy. The multiple energy emission source (11) may alternatively or additionally be used to calibrate (40) a dose calibrator (15).
