Evaluating the Effect of Injected Dose of 99mTc- MIBI on the Quantitative Parameters of Myocardial Perfusion Imaging

Background: 99mTc-MIBI cardiac perfusion scanning is recognized as a clinically useful method in evaluating coronary artery disease. By the implementation of new imaging techniques and systems, it seems possible to obtain high-quality images with a lower dose of radiopharmaceuticals. The purpose of this study was to evaluate the effect of injection dose of 99mTc-MIBI on quantitative parameters of cardiac perfusion scan. Materials and Methods: Eighty-three patients with the known probability of coronary artery disease were imaged three times (15, 120, and 180 min) after one injection during the stress phase. Assuming that 99mTc-MIBI has not any significant redistribution at this time, the only parameter which has been changed is the amount of accumulated radioactivity within the myocardium. In this way, we have three different images with different deposited doses in the myocardium from each patient. Then quantitative data of End Systolic Volume (ESV), End Diastolic Volume (EDV), and Ejection Fraction (EF) were calculated and compared. Results: Examination of quantitative scanning data indicates that the changes in EF data were non-significant and that the changes in ESV and EDV were significant over time. Conclusion: In this study, assuming a dose reduction of radioactivity up to 50% of the initial dose based on cumulative dose in myocardial and imaging time, no clinically significant changes in quantitative cardiac perfusion scan variables such as ESV, EDV and EF occurred.