A method for application of cross-calibration for a quantitative single photon emission computed tomography (SPECT) system, the method comprising: providing the SPECT system at a facility, with the SPECT system having one or more detectors configured to operate with different collimators to detect emissions from liquid radiotracers with injected dosages measured by well counters , the liquid radiotracers comprising isotopes; generating a first table of system specific planar sensitivities, the first table including one of the system specific planar sensitivities for each unique combination of isotope, energy of isotope, collimator , detector , and well counter ; generating a second table of cross-calibration factors, the second table including one of the cross-calibration factors for each unique combination of isotope, collimator , energy of the isotope, detector , and well counter , the cross-calibration factors being a function of the system specific planar sensitivities; receiving identities of a first one of the well counters used for a patient, a first one of the collimators used for the patient, a first one of the detectors used for the patient, a first one of the doses used for the patient, and a first one of the isotopes used for the patient; calculating a dose correction with a first one of the cross-calibration factors selected based on the identities; estimating the activity concentration in a patient having the first isotope at the first dose measured by the first well counter , the activity concentration estimated in a scan by the SPECT system using the first detector and first collimator and estimated as a function of the calculated dose correction; and generating an image of the activity concentration. providing the SPECT system at a facility, with the SPECT system having one or more detectors configured to operate with different collimators to detect emissions from liquid radiotracers with injected dosages measured by well counters , the liquid radiotracers comprising isotopes; generating a first table of system specific planar sensitivities, the first table including one of the system specific planar sensitivities for each unique combination of isotope, energy of isotope, collimator , detector , and well counter ; generating a second table of cross-calibration factors, the second table including one of the cross-calibration factors for each unique combination of isotope, collimator , energy of the isotope, detector , and well counter , the cross-calibration factors being a function of the system specific planar sensitivities; receiving identities of a first one of the well counters used for a patient, a first one of the collimators used for the patient, a first one of the detectors used for the patient, a first one of the doses used for the patient, and a first one of the isotopes used for the patient; calculating a dose correction with a first one of the cross-calibration factors selected based on the identities; estimating the activity concentration in a patient having the first isotope at the first dose measured by the first well counter , the activity concentration estimated in a scan by the SPECT system using the first detector and first collimator and estimated as a function of the calculated dose correction; and generating an image of the activity concentration. <EOS>