Subtraction of simultaneously acquired dual radionuclide images

The physical aspects of a simultaneous dual radionuclide technique incorporating computer subtraction for the diagnosis of infection using 67Ga citrate and 99mTc methylene diphosphonate (MDP) or sulfur colloid are considered. The efficacy of the data acquisition protocol and the interpretation of the subtracted images are shown to depend significantly on fundamental imaging system parameters. Measurement of these parameters using simple phantoms and their role in elucidating the technique is detailed. Subtracted images produced by three variations of the basic method arising from different normalization algorithms in current usage are compared. Simple phantoms are again used in assessing the accuracy of each variation. Clinical results are reported elsewhere.