Simultaneous acquisition of super(99m)Tc- and super(123)I-labeled radiotracers using a preclinical SPECT scanner with CZT detectors

Simultaneous acquisition of super(99m)Tc and super(123)I was evaluated using a preclinical SPECT scanner with cadmium zinc telluride (CZT)-based detectors. 10-ml cylindrical syringes contained about 37 MBq super(99m)Tc-tetrofosmin ( super(99m)Tc-TF) or 37 MBq super(123)I-15-(p-iodophenyl)- 3R,S-methyl pentadecanoic acid ( super(123)I-BMIPP) were used to assess the relationship between these SPECT radioactive counts and radioactivity. Two 10-ml syringes contained 100 or 300 MBq super(99m)Tc-TF and 100 MBq super(123)I-BMIPP to assess the influence of super(99m)Tc upscatter and super(123)I downscatter, respectively. A rat-sized cylindrical phantom also contained both 100 or 300 MBq super(99m)Tc-TF and 100 MBq super(123)I-BMIPP. The two 10-ml syringes and phantom were scanned using a pinhole collimator for rats. Myocardial infarction model rats were examined using 300 MBq super(99m)Tc-TF and 100 MBq super(123)I-BMIPP. Two 1-ml syringes contained 105 MBq super(99m)Tc-labeled hexamethylpropyleneamine oxime ( super(99m)Tc-HMPAO) and 35 MBq super(123)I-labeled N- omega -fluoropropyl-2 beta -carbomethoxy-3 beta -(4-iodophenyl) nortropane ( super(123)I-FP-CIT). The two 1-ml syringes were scanned using a pinhole collimator for mice. Normal mice were examined using 105 MBq super(99m)Tc-HMPAO and 35 MBq super(123)I-FP-CIT. The relationship between SPECT radioactive counts and radioactivity was excellent. Downscatter contamination of super(123)I-BMIPP exhibited fewer radioactive counts for 300 MBq super(99m)Tc-TF without scatter correction (SC) in 125-150 keV. There was no upscatter contamination of super(99m)Tc-TF in 150-175 keV. In the rat-sized phantom, the radioactive count ratio decreased to 4.0 % for 300 MBq super(99m)Tc-TF without SC in 125-150 keV. In the rats, myocardial images and radioactive counts of super(99m)Tc-TF with the dual tracer were identical to those of the super(99m)Tc-TF single injection. Downscatter contamination of super(123)I-FP-CIT was 4.2 % without SC in 125-150 keV. In the first injection of super(99m)Tc-HMPAO and second injection of super(123)I-FP-CIT, brain images and radioactive counts of super(99m)Tc-HMPAO with the dual tracer in normal mice also were the similar to those of the super(99m)Tc-HMPAO single injection. In the first injection of super(123)I-FP-CIT and second injection of super(99m)Tc-HMPAO, the brain images and radioactive counts with the dual tracer were not much different from those of the super(123)I-FP-CIT single injecti