Effect of 360° and 180° rotation SPET acquisitions on myocardial polar map: Comparison of 201T1-, 99Tcm- and 123I-labelled radiopharmaceuticals

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Both 360° and 180° rotation acquisition methods have been used in myocardial single photon emission tomography (SPET) studies. We compared both methods using 20199Tcm- and 123I radiopharmaceuticals with phantoms and clinical models. Myocardial phantom studies with anterior and inferior defects were performed using 201Tl, 99Tcm and 123I. Clinical models of 14 typical situations, including normal subjects, patients with anterior or inferior defects and a high right hemi-diaphragm, were studied. The radiopharmaceuticals were 201T1, 99Tcm-sestamibi, 123I-BMIPP and 123I-MIBG. Four sets of 180° anterior rotation data with starting angles of (A) posterior, (B) LPO 30°, (C) LPO 60° and (D) left lateral direction were generated and compared with 360° rotation SPET. A polar map display was used for quantification. In phantom studies, the defect contrast on the map was higher in the anterior defect with 180° rotation than with 360° rotation. However, it was decreased in the inferior defect, particularly with 201T1, because of decreased wall activity around the defect. In the patient model with anterior or inferior defects, the defect contrast was improved with 180° SPET by up to 10%. A slight decrease in the normal region was also noted in the 180° reconstruction. The effect of diffuse liver activity on the inferior region depended on the rotation range. A patient with a high right hemi-diaphragm showed a lower inferior count with 360° SPET. In conclusion, the 360° acquisition was superior to the 180° acquisition in the phantom with defects. Clinically, the quantitative differences in radionuclide types 99Tcm, 123I or 201T1) were not significant for quantifying a moderate degree (50–60% of peak count) of defect. However, we note quantitative variation depending on the rotation range in the 180° method.

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