Assessment relation of myocardial detector counts and administered activity of 99mTc-SestaMIBI in MPI: The effects of body weight, BMI and gender

Abstract

Introduction: In myocardial perfusion imaging, reducing the number of photons in images of obese patients reduces image quality. To solve this problem, we need to inject the tracer activity according to the patients’ weight. This study aimed to investigate the relationship between myocardial detector counts with patients’ weight, BMI, and gender. Materials and Methods: 129 patients underwent myocardial perfusion imaging in a two-day stress-first protocol, but only rest images were included in this study. Multiplication factor (MF=0.13/AVGweight0.64 ) ×body weight(kg)+1-0.13×AVGweight0.36 ) was used to determine the amount of tracer activity to patients. The total of myocardial detector counts in the raw images was calculated from the summation of 32 projections for each patient. Multiple linear regression test was used to simultaneously examine the effects of gender, BMI, and weight on photon counts. To evaluate the effect of breast attenuation, the photon counts of 22 female patients in the Breast Up position were also assessed. Results: There was no significant relationship between photon counts and patients’ weight (p=0.129), and BMI (0.406) but gender had significant effects on photon counts and myocardial detector counts were higher in males (p=0.00). There was a statistically significant difference between the images of Breast Up and non-Breast Up position, and myocardial detector counts were higher in the breast-up imaging method(p=0.00). Conclusion: Using the formula mentioned above, the image quality is similar in obese and lean patients, but myocardial detector counts are higher in males and this formula needs to be adjusted according to the patient’s gender.