Cross-talk correction for dual radionuclide brain imaging with 99mTc and 123I

Dual radionuclide imaging is useful in many situations, yielding perfectly registered images of 2 different tracers. The case of ⁹⁹ Tc^m and ¹²³I offers particular difficulties due to the closeness of the 2 photopeaks (140 and 159 keV). The authors have developed and compared 3 different cross-talk correction methods based on 2 different approaches. The first approach is to do a simple interpolated background subtraction, based on either 5 or 4 energy windows. The second approach is to separate the correction into 3 different steps-background, scatter and cross-talk correction using 4 energy windows. The authors used line source studies to quantify the amount of cross-talk. The fraction of photon cross-talk was found to be ~4% for ⁹⁹Tc^m to ~8% for ¹²³I to ⁹⁹Tc^m. The scattered photon cross-talk was <1% for ⁹⁹Tc^m to ¹²³I, and 10-50% for ¹²³I to ⁹⁹Tc^m. The correction methods were evaluated using an anthropomorphic brain phantom, and also tested on a patient study