Small field of view nuclear imaging detector evaluation using Tc-99m and Ga-67 radioisotopes

In this work we report the imaging performance of a small field of view planar scintigraphic system for low and medium energy radiotracers imaging. 99mTc (140 keV) and 67Ga (93 keV (P1, 42%), 184 keV (P2, 21%), 300 keV (P3, 17%), 393 keV (P4, 5%)) radioisotopes were used to evaluate the nuclear imaging detector in terms of non-uniformity, energy resolution, system spatial resolution and system sensitivity. Moreover, detector's ability to reliably quantify activity variations in the useful field of view has been evaluated. Specific collimator for given photon energy range is needed, in order to reduce image degradation due to photon scattering and penetration. Three parallel hole collimators different in geometry were studied. Results show that all of them are suitable for 99mTc and 67Ga molecular imaging applications, given that only the first photopeak in the case of 67Ga has to be used for imaging. In this case, accurate quantitative information is obtained with all 3 collimators for both radioisotopes. For 99mTc the most appropriate collimator is the one with the thinner septa walls and the lower height, while for 67Ga the thickest septa and higher height collimator. Dual isotope imaging is applicable using appropriate energy windows and appropriate collimator depending on the application.