Factors Influencing the Uptake of ^99mTc-Sestamibi in Breast Tissue on Molecular Breast Imaging

The purpose of this study was to evaluate the impact of changes to a patient's prandial status, metabolic status (rest vs. exercise), and peripheral blood flow (via caffeine or warming) on the uptake of ^99mTc-sestamibi in breast tissue. Methods: A total of 154 subjects participated in 1 of 4 study groups that evaluated the effects of 4 types of intervention on the uptake of ^99mTc-sestamibi in breast tissue (effect of fasting, light exercise, caffeine, and peripheral warming). Molecular breast imaging wasperformed before and after each intervention. Count density was assessed in counts/cm²/MBq from the mediolateral oblique view in all studies. Results: Uptake of ^99mTc-sestamibi in breast tissue increased by approximately 25% from 6.6 counts/cm²/MBq in the fed state to 8.3 counts/cm²/MBq with fasting. Peripheral warming also resulted in an approximately 20%increase in count density from 9.1 to 10.9 counts/cm²/MBq. Conversely, exercise caused a 35% drop in count density relative to the resting state. Uptake did not seem to be influenced by caffeine and did not correlate with a patient's height, weight, or breast thickness. There was only a weak correlation between breast activity and body surface area. Conclusion: The combined effects of fastingand warming resulted in an approximately 50%increased uptake of ^99mTc-sestamibi in breast tissue relative to that observed in a reference group to whom no preparatory instructions had been given. Optimal patient preparation before administration of ^99mTc-sestamibi should permit a corresponding reduction in either acquisition time or required dose of ^99mTc-sestamibi.