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.