The effect of photon energy on tests of field uniformity in scintillation cameras: concise communication.

Although Co-57 is generally used for testing the field uniformity of scintillation cameras, the various photon energies of other radionuclides require uniform response throughout the entire range of energies to which a scintillation camera can respond. The use of Co-57, however, may not adequately demonstrate the field response, which may be uniform at 122 keV but not at other energies. Two scintillation camera systems were investigated in this regard by storing field-flood images, obtained at several photon energies, in a minicomputer. The stored data were analyzed using the Kolmogorov-Smirnov test, revealing that field uniformity may change with photon energy. One of the scintillation cameras showed a variation in field response with photon energy, whereas the other camera did not. These results, however, should not be extrapolated to other cameras of the same type. If a particular scintillation camera is to be used routinely with several energies, its performance should be tested with each one to provide assurance that valid information is being obtained. The effects of dynamic uniformity field correction remain to be evaluated.